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1 @c Copyright (C) 2004-2017 Free Software Foundation, Inc.
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2 @c This is part of the GNU Fortran manual.
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3 @c For copying conditions, see the file gfortran.texi.
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4
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5 @ignore
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6 @c man begin COPYRIGHT
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7 Copyright @copyright{} 2004-2017 Free Software Foundation, Inc.
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8
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9 Permission is granted to copy, distribute and/or modify this document
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10 under the terms of the GNU Free Documentation License, Version 1.3 or
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11 any later version published by the Free Software Foundation; with the
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12 Invariant Sections being ``Funding Free Software'', the Front-Cover
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13 Texts being (a) (see below), and with the Back-Cover Texts being (b)
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14 (see below). A copy of the license is included in the gfdl(7) man page.
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15
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16 (a) The FSF's Front-Cover Text is:
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17
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18 A GNU Manual
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19
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20 (b) The FSF's Back-Cover Text is:
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21
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22 You have freedom to copy and modify this GNU Manual, like GNU
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23 software. Copies published by the Free Software Foundation raise
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24 funds for GNU development.
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25 @c man end
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26 @c Set file name and title for the man page.
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27 @setfilename gfortran
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28 @settitle GNU Fortran compiler.
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29 @c man begin SYNOPSIS
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30 gfortran [@option{-c}|@option{-S}|@option{-E}]
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31 [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
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32 [@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
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33 [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
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34 [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
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35 [@option{-f}@var{option}@dots{}]
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36 [@option{-m}@var{machine-option}@dots{}]
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37 [@option{-o} @var{outfile}] @var{infile}@dots{}
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38
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39 Only the most useful options are listed here; see below for the
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40 remainder.
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41 @c man end
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42 @c man begin SEEALSO
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43 gpl(7), gfdl(7), fsf-funding(7),
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44 cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
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45 and the Info entries for @file{gcc}, @file{cpp}, @file{gfortran}, @file{as},
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46 @file{ld}, @file{binutils} and @file{gdb}.
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47 @c man end
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48 @c man begin BUGS
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49 For instructions on reporting bugs, see
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50 @w{@value{BUGURL}}.
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51 @c man end
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52 @c man begin AUTHOR
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53 See the Info entry for @command{gfortran} for contributors to GCC and
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54 GNU Fortran.
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55 @c man end
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56 @end ignore
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57
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58 @node Invoking GNU Fortran
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59 @chapter GNU Fortran Command Options
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60 @cindex GNU Fortran command options
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61 @cindex command options
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62 @cindex options, @command{gfortran} command
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63
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64 @c man begin DESCRIPTION
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65
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66 The @command{gfortran} command supports all the options supported by the
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67 @command{gcc} command. Only options specific to GNU Fortran are documented
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68 here.
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69
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70 @xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
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71 Collection (GCC)}, for information
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72 on the non-Fortran-specific aspects of the @command{gcc} command (and,
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73 therefore, the @command{gfortran} command).
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74
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75 @cindex options, negative forms
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76 All GCC and GNU Fortran options
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77 are accepted both by @command{gfortran} and by @command{gcc}
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78 (as well as any other drivers built at the same time,
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79 such as @command{g++}),
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80 since adding GNU Fortran to the GCC distribution
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81 enables acceptance of GNU Fortran options
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82 by all of the relevant drivers.
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83
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84 In some cases, options have positive and negative forms;
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85 the negative form of @option{-ffoo} would be @option{-fno-foo}.
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86 This manual documents only one of these two forms, whichever
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87 one is not the default.
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88 @c man end
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89
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90 @menu
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91 * Option Summary:: Brief list of all @command{gfortran} options,
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92 without explanations.
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93 * Fortran Dialect Options:: Controlling the variant of Fortran language
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94 compiled.
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95 * Preprocessing Options:: Enable and customize preprocessing.
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96 * Error and Warning Options:: How picky should the compiler be?
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97 * Debugging Options:: Symbol tables, measurements, and debugging dumps.
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98 * Directory Options:: Where to find module files
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99 * Link Options :: Influencing the linking step
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100 * Runtime Options:: Influencing runtime behavior
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101 * Code Gen Options:: Specifying conventions for function calls, data layout
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102 and register usage.
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103 * Interoperability Options:: Options for interoperability with other
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104 languages.
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105 * Environment Variables:: Environment variables that affect @command{gfortran}.
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106 @end menu
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107
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108 @node Option Summary
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109 @section Option summary
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110
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111 @c man begin OPTIONS
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112
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113 Here is a summary of all the options specific to GNU Fortran, grouped
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114 by type. Explanations are in the following sections.
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115
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116 @table @emph
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117 @item Fortran Language Options
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118 @xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
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119 @gccoptlist{-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code @gol
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120 -fd-lines-as-comments @gol
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121 -fdec -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math @gol
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122 -fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
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123 -fdefault-real-10 -fdefault-real-16 -fdollar-ok -ffixed-line-length-@var{n} @gol
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124 -ffixed-line-length-none -ffree-form -ffree-line-length-@var{n} @gol
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125 -ffree-line-length-none -fimplicit-none -finteger-4-integer-8 @gol
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126 -fmax-identifier-length -fmodule-private -ffixed-form -fno-range-check @gol
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127 -fopenacc -fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 @gol
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128 -freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=@var{std}
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129 -ftest-forall-temp
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130 }
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131
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132 @item Preprocessing Options
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133 @xref{Preprocessing Options,,Enable and customize preprocessing}.
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134 @gccoptlist{-A-@var{question}@r{[}=@var{answer}@r{]}
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135 -A@var{question}=@var{answer} -C -CC -D@var{macro}@r{[}=@var{defn}@r{]}
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136 -H -P @gol
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137 -U@var{macro} -cpp -dD -dI -dM -dN -dU -fworking-directory
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138 -imultilib @var{dir} @gol
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139 -iprefix @var{file} -iquote -isysroot @var{dir} -isystem @var{dir} -nocpp
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140 -nostdinc @gol
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141 -undef
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142 }
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143
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144 @item Error and Warning Options
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145 @xref{Error and Warning Options,,Options to request or suppress errors
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146 and warnings}.
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147 @gccoptlist{-Waliasing -Wall -Wampersand -Wargument-mismatch -Warray-bounds
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148 -Wc-binding-type -Wcharacter-truncation -Wconversion @gol
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149 -Wdo-subscript -Wfunction-elimination -Wimplicit-interface @gol
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150 -Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only -Wintrinsics-std @gol
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151 -Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant @gol
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152 -Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all @gol
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153 -Wtarget-lifetime -fmax-errors=@var{n} -fsyntax-only -pedantic -pedantic-errors
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154 }
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155
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156 @item Debugging Options
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157 @xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
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158 @gccoptlist{-fbacktrace -fdump-fortran-optimized -fdump-fortran-original @gol
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159 -fdump-parse-tree -ffpe-trap=@var{list} -ffpe-summary=@var{list}
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160 }
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161
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162 @item Directory Options
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163 @xref{Directory Options,,Options for directory search}.
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164 @gccoptlist{-I@var{dir} -J@var{dir} -fintrinsic-modules-path @var{dir}}
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165
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166 @item Link Options
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167 @xref{Link Options,,Options for influencing the linking step}.
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168 @gccoptlist{-static-libgfortran}
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169
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170 @item Runtime Options
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171 @xref{Runtime Options,,Options for influencing runtime behavior}.
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172 @gccoptlist{-fconvert=@var{conversion} -fmax-subrecord-length=@var{length} @gol
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173 -frecord-marker=@var{length} -fsign-zero
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174 }
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175
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176 @item Interoperability Options
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177 @xref{Interoperability Options,,Options for interoperability}.
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178 @gccoptlist{-fc-prototypes}
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179
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180 @item Code Generation Options
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181 @xref{Code Gen Options,,Options for code generation conventions}.
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182 @gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
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183 -fbounds-check -fcheck-array-temporaries @gol
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184 -fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
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185 -fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c
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186 -ffrontend-optimize @gol
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187 -finit-character=@var{n} -finit-integer=@var{n} -finit-local-zero @gol
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188 -finit-derived @gol
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189 -finit-logical=@var{<true|false>}
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190 -finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
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191 -finline-matmul-limit=@var{n} @gol
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192 -fmax-array-constructor=@var{n} -fmax-stack-var-size=@var{n}
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193 -fno-align-commons @gol
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194 -fno-automatic -fno-protect-parens -fno-underscoring @gol
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195 -fsecond-underscore -fpack-derived -frealloc-lhs -frecursive @gol
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196 -frepack-arrays -fshort-enums -fstack-arrays
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197 }
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198 @end table
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199
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200 @node Fortran Dialect Options
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201 @section Options controlling Fortran dialect
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202 @cindex dialect options
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203 @cindex language, dialect options
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204 @cindex options, dialect
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205
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206 The following options control the details of the Fortran dialect
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207 accepted by the compiler:
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208
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209 @table @gcctabopt
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210 @item -ffree-form
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211 @itemx -ffixed-form
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212 @opindex @code{ffree-form}
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213 @opindex @code{ffixed-form}
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214 @cindex options, Fortran dialect
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215 @cindex file format, free
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216 @cindex file format, fixed
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217 Specify the layout used by the source file. The free form layout
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218 was introduced in Fortran 90. Fixed form was traditionally used in
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219 older Fortran programs. When neither option is specified, the source
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220 form is determined by the file extension.
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221
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222 @item -fall-intrinsics
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223 @opindex @code{fall-intrinsics}
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224 This option causes all intrinsic procedures (including the GNU-specific
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225 extensions) to be accepted. This can be useful with @option{-std=f95} to
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226 force standard-compliance but get access to the full range of intrinsics
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227 available with @command{gfortran}. As a consequence, @option{-Wintrinsics-std}
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228 will be ignored and no user-defined procedure with the same name as any
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229 intrinsic will be called except when it is explicitly declared @code{EXTERNAL}.
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230
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231 @item -fd-lines-as-code
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232 @itemx -fd-lines-as-comments
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233 @opindex @code{fd-lines-as-code}
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234 @opindex @code{fd-lines-as-comments}
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235 Enable special treatment for lines beginning with @code{d} or @code{D}
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236 in fixed form sources. If the @option{-fd-lines-as-code} option is
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237 given they are treated as if the first column contained a blank. If the
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238 @option{-fd-lines-as-comments} option is given, they are treated as
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239 comment lines.
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240
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241 @item -fdec
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242 @opindex @code{fdec}
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243 DEC compatibility mode. Enables extensions and other features that mimic
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244 the default behavior of older compilers (such as DEC).
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245 These features are non-standard and should be avoided at all costs.
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246 For details on GNU Fortran's implementation of these extensions see the
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247 full documentation.
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248
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249 Other flags enabled by this switch are:
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250 @option{-fdollar-ok} @option{-fcray-pointer} @option{-fdec-structure}
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251 @option{-fdec-intrinsic-ints} @option{-fdec-static} @option{-fdec-math}
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252
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253 If @option{-fd-lines-as-code}/@option{-fd-lines-as-comments} are unset, then
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254 @option{-fdec} also sets @option{-fd-lines-as-comments}.
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255
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256 @item -fdec-structure
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257 @opindex @code{fdec-structure}
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258 Enable DEC @code{STRUCTURE} and @code{RECORD} as well as @code{UNION},
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259 @code{MAP}, and dot ('.') as a member separator (in addition to '%'). This is
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260 provided for compatibility only; Fortran 90 derived types should be used
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261 instead where possible.
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262
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263 @item -fdec-intrinsic-ints
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264 @opindex @code{fdec-intrinsic-ints}
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265 Enable B/I/J/K kind variants of existing integer functions (e.g. BIAND, IIAND,
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266 JIAND, etc...). For a complete list of intrinsics see the full documentation.
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267
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268 @item -fdec-math
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269 @opindex @code{fdec-math}
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270 Enable legacy math intrinsics such as COTAN and degree-valued trigonometric
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271 functions (e.g. TAND, ATAND, etc...) for compatability with older code.
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272
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273 @item -fdec-static
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274 @opindex @code{fdec-static}
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275 Enable DEC-style STATIC and AUTOMATIC attributes to explicitly specify
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276 the storage of variables and other objects.
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277
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278 @item -fdollar-ok
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279 @opindex @code{fdollar-ok}
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280 @cindex @code{$}
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281 @cindex symbol names
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282 @cindex character set
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283 Allow @samp{$} as a valid non-first character in a symbol name. Symbols
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284 that start with @samp{$} are rejected since it is unclear which rules to
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285 apply to implicit typing as different vendors implement different rules.
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286 Using @samp{$} in @code{IMPLICIT} statements is also rejected.
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287
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288 @item -fbackslash
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289 @opindex @code{backslash}
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290 @cindex backslash
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291 @cindex escape characters
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292 Change the interpretation of backslashes in string literals from a single
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293 backslash character to ``C-style'' escape characters. The following
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294 combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n},
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295 @code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII
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296 characters alert, backspace, form feed, newline, carriage return,
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297 horizontal tab, vertical tab, backslash, and NUL, respectively.
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298 Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and
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299 @code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are
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300 translated into the Unicode characters corresponding to the specified code
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301 points. All other combinations of a character preceded by \ are
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302 unexpanded.
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303
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304 @item -fmodule-private
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305 @opindex @code{fmodule-private}
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306 @cindex module entities
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307 @cindex private
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308 Set the default accessibility of module entities to @code{PRIVATE}.
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309 Use-associated entities will not be accessible unless they are explicitly
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310 declared as @code{PUBLIC}.
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311
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312 @item -ffixed-line-length-@var{n}
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313 @opindex @code{ffixed-line-length-}@var{n}
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314 @cindex file format, fixed
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315 Set column after which characters are ignored in typical fixed-form
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316 lines in the source file, and through which spaces are assumed (as
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317 if padded to that length) after the ends of short fixed-form lines.
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318
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319 Popular values for @var{n} include 72 (the
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320 standard and the default), 80 (card image), and 132 (corresponding
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321 to ``extended-source'' options in some popular compilers).
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322 @var{n} may also be @samp{none}, meaning that the entire line is meaningful
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323 and that continued character constants never have implicit spaces appended
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324 to them to fill out the line.
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325 @option{-ffixed-line-length-0} means the same thing as
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326 @option{-ffixed-line-length-none}.
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327
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328 @item -ffree-line-length-@var{n}
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329 @opindex @code{ffree-line-length-}@var{n}
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330 @cindex file format, free
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331 Set column after which characters are ignored in typical free-form
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332 lines in the source file. The default value is 132.
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333 @var{n} may be @samp{none}, meaning that the entire line is meaningful.
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334 @option{-ffree-line-length-0} means the same thing as
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335 @option{-ffree-line-length-none}.
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336
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337 @item -fmax-identifier-length=@var{n}
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338 @opindex @code{fmax-identifier-length=}@var{n}
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339 Specify the maximum allowed identifier length. Typical values are
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340 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
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341
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342 @item -fimplicit-none
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343 @opindex @code{fimplicit-none}
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344 Specify that no implicit typing is allowed, unless overridden by explicit
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345 @code{IMPLICIT} statements. This is the equivalent of adding
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346 @code{implicit none} to the start of every procedure.
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347
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348 @item -fcray-pointer
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349 @opindex @code{fcray-pointer}
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|
|
350 Enable the Cray pointer extension, which provides C-like pointer
|
|
|
351 functionality.
|
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|
352
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|
|
353 @item -fopenacc
|
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|
354 @opindex @code{fopenacc}
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355 @cindex OpenACC
|
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|
356 Enable the OpenACC extensions. This includes OpenACC @code{!$acc}
|
|
|
357 directives in free form and @code{c$acc}, @code{*$acc} and
|
|
|
358 @code{!$acc} directives in fixed form, @code{!$} conditional
|
|
|
359 compilation sentinels in free form and @code{c$}, @code{*$} and
|
|
|
360 @code{!$} sentinels in fixed form, and when linking arranges for the
|
|
|
361 OpenACC runtime library to be linked in.
|
|
|
362
|
|
|
363 Note that this is an experimental feature, incomplete, and subject to
|
|
|
364 change in future versions of GCC. See
|
|
|
365 @w{@uref{https://gcc.gnu.org/wiki/OpenACC}} for more information.
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|
366
|
|
|
367 @item -fopenmp
|
|
|
368 @opindex @code{fopenmp}
|
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|
369 @cindex OpenMP
|
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|
370 Enable the OpenMP extensions. This includes OpenMP @code{!$omp} directives
|
|
|
371 in free form
|
|
|
372 and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
|
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373 @code{!$} conditional compilation sentinels in free form
|
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374 and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form,
|
|
|
375 and when linking arranges for the OpenMP runtime library to be linked
|
|
|
376 in. The option @option{-fopenmp} implies @option{-frecursive}.
|
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377
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|
|
378 @item -fno-range-check
|
|
|
379 @opindex @code{frange-check}
|
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|
380 Disable range checking on results of simplification of constant
|
|
|
381 expressions during compilation. For example, GNU Fortran will give
|
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|
382 an error at compile time when simplifying @code{a = 1. / 0}.
|
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|
383 With this option, no error will be given and @code{a} will be assigned
|
|
|
384 the value @code{+Infinity}. If an expression evaluates to a value
|
|
|
385 outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}],
|
|
|
386 then the expression will be replaced by @code{-Inf} or @code{+Inf}
|
|
|
387 as appropriate.
|
|
|
388 Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow
|
|
|
389 on most systems, but with @option{-fno-range-check} the value will
|
|
|
390 ``wrap around'' and @code{i} will be initialized to @math{-1} instead.
|
|
|
391
|
|
|
392 @item -fdefault-integer-8
|
|
|
393 @opindex @code{fdefault-integer-8}
|
|
|
394 Set the default integer and logical types to an 8 byte wide type. This option
|
|
|
395 also affects the kind of integer constants like @code{42}. Unlike
|
|
|
396 @option{-finteger-4-integer-8}, it does not promote variables with explicit
|
|
|
397 kind declaration.
|
|
|
398
|
|
|
399 @item -fdefault-real-8
|
|
|
400 @opindex @code{fdefault-real-8}
|
|
|
401 Set the default real type to an 8 byte wide type. This option also affects
|
|
|
402 the kind of non-double real constants like @code{1.0}, and does promote
|
|
|
403 the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
|
|
|
404 @code{-fdefault-double-8} is given, too. Unlike @option{-freal-4-real-8},
|
|
|
405 it does not promote variables with explicit kind declaration.
|
|
|
406
|
|
|
407 @item -fdefault-real-10
|
|
|
408 @opindex @code{fdefault-real-10}
|
|
|
409 Set the default real type to a 10 byte wide type. This option also affects
|
|
|
410 the kind of non-double real constants like @code{1.0}, and does promote
|
|
|
411 the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
|
|
|
412 @code{-fdefault-double-8} is given. Unlike @option{-freal-4-real-10},
|
|
|
413 it does not promote variables with explicit kind declaration.
|
|
|
414
|
|
|
415 @item -fdefault-real-16
|
|
|
416 @opindex @code{fdefault-real-16}
|
|
|
417 Set the default real type to a 16 byte wide type. This option also affects
|
|
|
418 the kind of non-double real constants like @code{1.0}, and does promote
|
|
|
419 the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
|
|
|
420 @code{-fdefault-double-8} is given. Unlike @option{-freal-4-real-16},
|
|
|
421 it does not promote variables with explicit kind declaration.
|
|
|
422
|
|
|
423 @item -fdefault-double-8
|
|
|
424 @opindex @code{fdefault-double-8}
|
|
|
425 Set the @code{DOUBLE PRECISION} type to an 8 byte wide type. Do nothing if this
|
|
|
426 is already the default. If @option{-fdefault-real-8} is given,
|
|
|
427 @code{DOUBLE PRECISION} would instead be promoted to 16 bytes if possible, and
|
|
|
428 @option{-fdefault-double-8} can be used to prevent this. The kind of real
|
|
|
429 constants like @code{1.d0} will not be changed by @option{-fdefault-real-8}
|
|
|
430 though, so also @option{-fdefault-double-8} does not affect it.
|
|
|
431
|
|
|
432 @item -finteger-4-integer-8
|
|
|
433 @opindex @code{finteger-4-integer-8}
|
|
|
434 Promote all @code{INTEGER(KIND=4)} entities to an @code{INTEGER(KIND=8)}
|
|
|
435 entities. If @code{KIND=8} is unavailable, then an error will be issued.
|
|
|
436 This option should be used with care and may not be suitable for your codes.
|
|
|
437 Areas of possible concern include calls to external procedures,
|
|
|
438 alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
|
|
|
439 BOZ literal constant conversion, and I/O. Inspection of the intermediate
|
|
|
440 representation of the translated Fortran code, produced by
|
|
|
441 @option{-fdump-tree-original}, is suggested.
|
|
|
442
|
|
|
443 @item -freal-4-real-8
|
|
|
444 @itemx -freal-4-real-10
|
|
|
445 @itemx -freal-4-real-16
|
|
|
446 @itemx -freal-8-real-4
|
|
|
447 @itemx -freal-8-real-10
|
|
|
448 @itemx -freal-8-real-16
|
|
|
449 @opindex @code{freal-4-real-8}
|
|
|
450 @opindex @code{freal-4-real-10}
|
|
|
451 @opindex @code{freal-4-real-16}
|
|
|
452 @opindex @code{freal-8-real-4}
|
|
|
453 @opindex @code{freal-8-real-10}
|
|
|
454 @opindex @code{freal-8-real-16}
|
|
|
455 @cindex options, real kind type promotion
|
|
|
456 Promote all @code{REAL(KIND=M)} entities to @code{REAL(KIND=N)} entities.
|
|
|
457 If @code{REAL(KIND=N)} is unavailable, then an error will be issued.
|
|
|
458 All other real kind types are unaffected by this option.
|
|
|
459 These options should be used with care and may not be suitable for your
|
|
|
460 codes. Areas of possible concern include calls to external procedures,
|
|
|
461 alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
|
|
|
462 BOZ literal constant conversion, and I/O. Inspection of the intermediate
|
|
|
463 representation of the translated Fortran code, produced by
|
|
|
464 @option{-fdump-tree-original}, is suggested.
|
|
|
465
|
|
|
466 @item -std=@var{std}
|
|
|
467 @opindex @code{std=}@var{std} option
|
|
|
468 Specify the standard to which the program is expected to conform, which
|
|
|
469 may be one of @samp{f95}, @samp{f2003}, @samp{f2008}, @samp{gnu}, or
|
|
|
470 @samp{legacy}. The default value for @var{std} is @samp{gnu}, which
|
|
|
471 specifies a superset of the Fortran 95 standard that includes all of the
|
|
|
472 extensions supported by GNU Fortran, although warnings will be given for
|
|
|
473 obsolete extensions not recommended for use in new code. The
|
|
|
474 @samp{legacy} value is equivalent but without the warnings for obsolete
|
|
|
475 extensions, and may be useful for old non-standard programs. The
|
|
|
476 @samp{f95}, @samp{f2003} and @samp{f2008} values specify strict
|
|
|
477 conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards,
|
|
|
478 respectively; errors are given for all extensions beyond the relevant
|
|
|
479 language standard, and warnings are given for the Fortran 77 features
|
|
|
480 that are permitted but obsolescent in later standards. @samp{-std=f2008ts}
|
|
|
481 allows the Fortran 2008 standard including the additions of the
|
|
|
482 Technical Specification (TS) 29113 on Further Interoperability of Fortran
|
|
|
483 with C and TS 18508 on Additional Parallel Features in Fortran.
|
|
|
484
|
|
|
485 @item -ftest-forall-temp
|
|
|
486 @opindex @code{ftest-forall-temp}
|
|
|
487 Enhance test coverage by forcing most forall assignments to use temporary.
|
|
|
488
|
|
|
489 @end table
|
|
|
490
|
|
|
491 @node Preprocessing Options
|
|
|
492 @section Enable and customize preprocessing
|
|
|
493 @cindex preprocessor
|
|
|
494 @cindex options, preprocessor
|
|
|
495 @cindex CPP
|
|
|
496
|
|
|
497 Preprocessor related options. See section
|
|
|
498 @ref{Preprocessing and conditional compilation} for more detailed
|
|
|
499 information on preprocessing in @command{gfortran}.
|
|
|
500
|
|
|
501 @table @gcctabopt
|
|
|
502 @item -cpp
|
|
|
503 @itemx -nocpp
|
|
|
504 @opindex @code{cpp}
|
|
|
505 @opindex @code{fpp}
|
|
|
506 @cindex preprocessor, enable
|
|
|
507 @cindex preprocessor, disable
|
|
|
508 Enable preprocessing. The preprocessor is automatically invoked if
|
|
|
509 the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR},
|
|
|
510 @file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use
|
|
|
511 this option to manually enable preprocessing of any kind of Fortran file.
|
|
|
512
|
|
|
513 To disable preprocessing of files with any of the above listed extensions,
|
|
|
514 use the negative form: @option{-nocpp}.
|
|
|
515
|
|
|
516 The preprocessor is run in traditional mode. Any restrictions of the
|
|
|
517 file-format, especially the limits on line length, apply for
|
|
|
518 preprocessed output as well, so it might be advisable to use the
|
|
|
519 @option{-ffree-line-length-none} or @option{-ffixed-line-length-none}
|
|
|
520 options.
|
|
|
521
|
|
|
522 @item -dM
|
|
|
523 @opindex @code{dM}
|
|
|
524 @cindex preprocessor, debugging
|
|
|
525 @cindex debugging, preprocessor
|
|
|
526 Instead of the normal output, generate a list of @code{'#define'}
|
|
|
527 directives for all the macros defined during the execution of the
|
|
|
528 preprocessor, including predefined macros. This gives you a way
|
|
|
529 of finding out what is predefined in your version of the preprocessor.
|
|
|
530 Assuming you have no file @file{foo.f90}, the command
|
|
|
531 @smallexample
|
|
|
532 touch foo.f90; gfortran -cpp -E -dM foo.f90
|
|
|
533 @end smallexample
|
|
|
534 will show all the predefined macros.
|
|
|
535
|
|
|
536 @item -dD
|
|
|
537 @opindex @code{dD}
|
|
|
538 @cindex preprocessor, debugging
|
|
|
539 @cindex debugging, preprocessor
|
|
|
540 Like @option{-dM} except in two respects: it does not include the
|
|
|
541 predefined macros, and it outputs both the @code{#define} directives
|
|
|
542 and the result of preprocessing. Both kinds of output go to the
|
|
|
543 standard output file.
|
|
|
544
|
|
|
545 @item -dN
|
|
|
546 @opindex @code{dN}
|
|
|
547 @cindex preprocessor, debugging
|
|
|
548 @cindex debugging, preprocessor
|
|
|
549 Like @option{-dD}, but emit only the macro names, not their expansions.
|
|
|
550
|
|
|
551 @item -dU
|
|
|
552 @opindex @code{dU}
|
|
|
553 @cindex preprocessor, debugging
|
|
|
554 @cindex debugging, preprocessor
|
|
|
555 Like @option{dD} except that only macros that are expanded, or whose
|
|
|
556 definedness is tested in preprocessor directives, are output; the
|
|
|
557 output is delayed until the use or test of the macro; and @code{'#undef'}
|
|
|
558 directives are also output for macros tested but undefined at the time.
|
|
|
559
|
|
|
560 @item -dI
|
|
|
561 @opindex @code{dI}
|
|
|
562 @cindex preprocessor, debugging
|
|
|
563 @cindex debugging, preprocessor
|
|
|
564 Output @code{'#include'} directives in addition to the result
|
|
|
565 of preprocessing.
|
|
|
566
|
|
|
567 @item -fworking-directory
|
|
|
568 @opindex @code{fworking-directory}
|
|
|
569 @cindex preprocessor, working directory
|
|
|
570 Enable generation of linemarkers in the preprocessor output that will
|
|
|
571 let the compiler know the current working directory at the time of
|
|
|
572 preprocessing. When this option is enabled, the preprocessor will emit,
|
|
|
573 after the initial linemarker, a second linemarker with the current
|
|
|
574 working directory followed by two slashes. GCC will use this directory,
|
|
|
575 when it is present in the preprocessed input, as the directory emitted
|
|
|
576 as the current working directory in some debugging information formats.
|
|
|
577 This option is implicitly enabled if debugging information is enabled,
|
|
|
578 but this can be inhibited with the negated form
|
|
|
579 @option{-fno-working-directory}. If the @option{-P} flag is present
|
|
|
580 in the command line, this option has no effect, since no @code{#line}
|
|
|
581 directives are emitted whatsoever.
|
|
|
582
|
|
|
583 @item -idirafter @var{dir}
|
|
|
584 @opindex @code{idirafter @var{dir}}
|
|
|
585 @cindex preprocessing, include path
|
|
|
586 Search @var{dir} for include files, but do it after all directories
|
|
|
587 specified with @option{-I} and the standard system directories have
|
|
|
588 been exhausted. @var{dir} is treated as a system include directory.
|
|
|
589 If dir begins with @code{=}, then the @code{=} will be replaced by
|
|
|
590 the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
|
|
|
591
|
|
|
592 @item -imultilib @var{dir}
|
|
|
593 @opindex @code{imultilib @var{dir}}
|
|
|
594 @cindex preprocessing, include path
|
|
|
595 Use @var{dir} as a subdirectory of the directory containing target-specific
|
|
|
596 C++ headers.
|
|
|
597
|
|
|
598 @item -iprefix @var{prefix}
|
|
|
599 @opindex @code{iprefix @var{prefix}}
|
|
|
600 @cindex preprocessing, include path
|
|
|
601 Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
|
|
|
602 options. If the @var{prefix} represents a directory, you should include
|
|
|
603 the final @code{'/'}.
|
|
|
604
|
|
|
605 @item -isysroot @var{dir}
|
|
|
606 @opindex @code{isysroot @var{dir}}
|
|
|
607 @cindex preprocessing, include path
|
|
|
608 This option is like the @option{--sysroot} option, but applies only to
|
|
|
609 header files. See the @option{--sysroot} option for more information.
|
|
|
610
|
|
|
611 @item -iquote @var{dir}
|
|
|
612 @opindex @code{iquote @var{dir}}
|
|
|
613 @cindex preprocessing, include path
|
|
|
614 Search @var{dir} only for header files requested with @code{#include "file"};
|
|
|
615 they are not searched for @code{#include <file>}, before all directories
|
|
|
616 specified by @option{-I} and before the standard system directories. If
|
|
|
617 @var{dir} begins with @code{=}, then the @code{=} will be replaced by the
|
|
|
618 sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
|
|
|
619
|
|
|
620 @item -isystem @var{dir}
|
|
|
621 @opindex @code{isystem @var{dir}}
|
|
|
622 @cindex preprocessing, include path
|
|
|
623 Search @var{dir} for header files, after all directories specified by
|
|
|
624 @option{-I} but before the standard system directories. Mark it as a
|
|
|
625 system directory, so that it gets the same special treatment as is
|
|
|
626 applied to the standard system directories. If @var{dir} begins with
|
|
|
627 @code{=}, then the @code{=} will be replaced by the sysroot prefix;
|
|
|
628 see @option{--sysroot} and @option{-isysroot}.
|
|
|
629
|
|
|
630 @item -nostdinc
|
|
|
631 @opindex @code{nostdinc}
|
|
|
632 Do not search the standard system directories for header files. Only
|
|
|
633 the directories you have specified with @option{-I} options (and the
|
|
|
634 directory of the current file, if appropriate) are searched.
|
|
|
635
|
|
|
636 @item -undef
|
|
|
637 @opindex @code{undef}
|
|
|
638 Do not predefine any system-specific or GCC-specific macros.
|
|
|
639 The standard predefined macros remain defined.
|
|
|
640
|
|
|
641 @item -A@var{predicate}=@var{answer}
|
|
|
642 @opindex @code{A@var{predicate}=@var{answer}}
|
|
|
643 @cindex preprocessing, assertion
|
|
|
644 Make an assertion with the predicate @var{predicate} and answer @var{answer}.
|
|
|
645 This form is preferred to the older form -A predicate(answer), which is still
|
|
|
646 supported, because it does not use shell special characters.
|
|
|
647
|
|
|
648 @item -A-@var{predicate}=@var{answer}
|
|
|
649 @opindex @code{A-@var{predicate}=@var{answer}}
|
|
|
650 @cindex preprocessing, assertion
|
|
|
651 Cancel an assertion with the predicate @var{predicate} and answer @var{answer}.
|
|
|
652
|
|
|
653 @item -C
|
|
|
654 @opindex @code{C}
|
|
|
655 @cindex preprocessing, keep comments
|
|
|
656 Do not discard comments. All comments are passed through to the output
|
|
|
657 file, except for comments in processed directives, which are deleted
|
|
|
658 along with the directive.
|
|
|
659
|
|
|
660 You should be prepared for side effects when using @option{-C}; it causes
|
|
|
661 the preprocessor to treat comments as tokens in their own right. For example,
|
|
|
662 comments appearing at the start of what would be a directive line have the
|
|
|
663 effect of turning that line into an ordinary source line, since the first
|
|
|
664 token on the line is no longer a @code{'#'}.
|
|
|
665
|
|
|
666 Warning: this currently handles C-Style comments only. The preprocessor
|
|
|
667 does not yet recognize Fortran-style comments.
|
|
|
668
|
|
|
669 @item -CC
|
|
|
670 @opindex @code{CC}
|
|
|
671 @cindex preprocessing, keep comments
|
|
|
672 Do not discard comments, including during macro expansion. This is like
|
|
|
673 @option{-C}, except that comments contained within macros are also passed
|
|
|
674 through to the output file where the macro is expanded.
|
|
|
675
|
|
|
676 In addition to the side-effects of the @option{-C} option, the @option{-CC}
|
|
|
677 option causes all C++-style comments inside a macro to be converted to C-style
|
|
|
678 comments. This is to prevent later use of that macro from inadvertently
|
|
|
679 commenting out the remainder of the source line. The @option{-CC} option
|
|
|
680 is generally used to support lint comments.
|
|
|
681
|
|
|
682 Warning: this currently handles C- and C++-Style comments only. The
|
|
|
683 preprocessor does not yet recognize Fortran-style comments.
|
|
|
684
|
|
|
685 @item -D@var{name}
|
|
|
686 @opindex @code{D@var{name}}
|
|
|
687 @cindex preprocessing, define macros
|
|
|
688 Predefine name as a macro, with definition @code{1}.
|
|
|
689
|
|
|
690 @item -D@var{name}=@var{definition}
|
|
|
691 @opindex @code{D@var{name}=@var{definition}}
|
|
|
692 @cindex preprocessing, define macros
|
|
|
693 The contents of @var{definition} are tokenized and processed as if they
|
|
|
694 appeared during translation phase three in a @code{'#define'} directive.
|
|
|
695 In particular, the definition will be truncated by embedded newline
|
|
|
696 characters.
|
|
|
697
|
|
|
698 If you are invoking the preprocessor from a shell or shell-like program
|
|
|
699 you may need to use the shell's quoting syntax to protect characters such
|
|
|
700 as spaces that have a meaning in the shell syntax.
|
|
|
701
|
|
|
702 If you wish to define a function-like macro on the command line, write
|
|
|
703 its argument list with surrounding parentheses before the equals sign
|
|
|
704 (if any). Parentheses are meaningful to most shells, so you will need
|
|
|
705 to quote the option. With sh and csh, @code{-D'name(args...)=definition'}
|
|
|
706 works.
|
|
|
707
|
|
|
708 @option{-D} and @option{-U} options are processed in the order they are
|
|
|
709 given on the command line. All -imacros file and -include file options
|
|
|
710 are processed after all -D and -U options.
|
|
|
711
|
|
|
712 @item -H
|
|
|
713 @opindex @code{H}
|
|
|
714 Print the name of each header file used, in addition to other normal
|
|
|
715 activities. Each name is indented to show how deep in the @code{'#include'}
|
|
|
716 stack it is.
|
|
|
717
|
|
|
718 @item -P
|
|
|
719 @opindex @code{P}
|
|
|
720 @cindex preprocessing, no linemarkers
|
|
|
721 Inhibit generation of linemarkers in the output from the preprocessor.
|
|
|
722 This might be useful when running the preprocessor on something that
|
|
|
723 is not C code, and will be sent to a program which might be confused
|
|
|
724 by the linemarkers.
|
|
|
725
|
|
|
726 @item -U@var{name}
|
|
|
727 @opindex @code{U@var{name}}
|
|
|
728 @cindex preprocessing, undefine macros
|
|
|
729 Cancel any previous definition of @var{name}, either built in or provided
|
|
|
730 with a @option{-D} option.
|
|
|
731 @end table
|
|
|
732
|
|
|
733
|
|
|
734 @node Error and Warning Options
|
|
|
735 @section Options to request or suppress errors and warnings
|
|
|
736 @cindex options, warnings
|
|
|
737 @cindex options, errors
|
|
|
738 @cindex warnings, suppressing
|
|
|
739 @cindex messages, error
|
|
|
740 @cindex messages, warning
|
|
|
741 @cindex suppressing warnings
|
|
|
742
|
|
|
743 Errors are diagnostic messages that report that the GNU Fortran compiler
|
|
|
744 cannot compile the relevant piece of source code. The compiler will
|
|
|
745 continue to process the program in an attempt to report further errors
|
|
|
746 to aid in debugging, but will not produce any compiled output.
|
|
|
747
|
|
|
748 Warnings are diagnostic messages that report constructions which
|
|
|
749 are not inherently erroneous but which are risky or suggest there is
|
|
|
750 likely to be a bug in the program. Unless @option{-Werror} is specified,
|
|
|
751 they do not prevent compilation of the program.
|
|
|
752
|
|
|
753 You can request many specific warnings with options beginning @option{-W},
|
|
|
754 for example @option{-Wimplicit} to request warnings on implicit
|
|
|
755 declarations. Each of these specific warning options also has a
|
|
|
756 negative form beginning @option{-Wno-} to turn off warnings;
|
|
|
757 for example, @option{-Wno-implicit}. This manual lists only one of the
|
|
|
758 two forms, whichever is not the default.
|
|
|
759
|
|
|
760 These options control the amount and kinds of errors and warnings produced
|
|
|
761 by GNU Fortran:
|
|
|
762
|
|
|
763 @table @gcctabopt
|
|
|
764 @item -fmax-errors=@var{n}
|
|
|
765 @opindex @code{fmax-errors=}@var{n}
|
|
|
766 @cindex errors, limiting
|
|
|
767 Limits the maximum number of error messages to @var{n}, at which point
|
|
|
768 GNU Fortran bails out rather than attempting to continue processing the
|
|
|
769 source code. If @var{n} is 0, there is no limit on the number of error
|
|
|
770 messages produced.
|
|
|
771
|
|
|
772 @item -fsyntax-only
|
|
|
773 @opindex @code{fsyntax-only}
|
|
|
774 @cindex syntax checking
|
|
|
775 Check the code for syntax errors, but do not actually compile it. This
|
|
|
776 will generate module files for each module present in the code, but no
|
|
|
777 other output file.
|
|
|
778
|
|
|
779 @item -Wpedantic
|
|
|
780 @itemx -pedantic
|
|
|
781 @opindex @code{pedantic}
|
|
|
782 @opindex @code{Wpedantic}
|
|
|
783 Issue warnings for uses of extensions to Fortran 95.
|
|
|
784 @option{-pedantic} also applies to C-language constructs where they
|
|
|
785 occur in GNU Fortran source files, such as use of @samp{\e} in a
|
|
|
786 character constant within a directive like @code{#include}.
|
|
|
787
|
|
|
788 Valid Fortran 95 programs should compile properly with or without
|
|
|
789 this option.
|
|
|
790 However, without this option, certain GNU extensions and traditional
|
|
|
791 Fortran features are supported as well.
|
|
|
792 With this option, many of them are rejected.
|
|
|
793
|
|
|
794 Some users try to use @option{-pedantic} to check programs for conformance.
|
|
|
795 They soon find that it does not do quite what they want---it finds some
|
|
|
796 nonstandard practices, but not all.
|
|
|
797 However, improvements to GNU Fortran in this area are welcome.
|
|
|
798
|
|
|
799 This should be used in conjunction with @option{-std=f95},
|
|
|
800 @option{-std=f2003} or @option{-std=f2008}.
|
|
|
801
|
|
|
802 @item -pedantic-errors
|
|
|
803 @opindex @code{pedantic-errors}
|
|
|
804 Like @option{-pedantic}, except that errors are produced rather than
|
|
|
805 warnings.
|
|
|
806
|
|
|
807 @item -Wall
|
|
|
808 @opindex @code{Wall}
|
|
|
809 @cindex all warnings
|
|
|
810 @cindex warnings, all
|
|
|
811 Enables commonly used warning options pertaining to usage that
|
|
|
812 we recommend avoiding and that we believe are easy to avoid.
|
|
|
813 This currently includes @option{-Waliasing}, @option{-Wampersand},
|
|
|
814 @option{-Wconversion}, @option{-Wsurprising}, @option{-Wc-binding-type},
|
|
|
815 @option{-Wintrinsics-std}, @option{-Wtabs}, @option{-Wintrinsic-shadow},
|
|
|
816 @option{-Wline-truncation}, @option{-Wtarget-lifetime},
|
|
|
817 @option{-Winteger-division}, @option{-Wreal-q-constant}, @option{-Wunused}
|
|
|
818 and @option{-Wundefined-do-loop}.
|
|
|
819
|
|
|
820 @item -Waliasing
|
|
|
821 @opindex @code{Waliasing}
|
|
|
822 @cindex aliasing
|
|
|
823 @cindex warnings, aliasing
|
|
|
824 Warn about possible aliasing of dummy arguments. Specifically, it warns
|
|
|
825 if the same actual argument is associated with a dummy argument with
|
|
|
826 @code{INTENT(IN)} and a dummy argument with @code{INTENT(OUT)} in a call
|
|
|
827 with an explicit interface.
|
|
|
828
|
|
|
829 The following example will trigger the warning.
|
|
|
830 @smallexample
|
|
|
831 interface
|
|
|
832 subroutine bar(a,b)
|
|
|
833 integer, intent(in) :: a
|
|
|
834 integer, intent(out) :: b
|
|
|
835 end subroutine
|
|
|
836 end interface
|
|
|
837 integer :: a
|
|
|
838
|
|
|
839 call bar(a,a)
|
|
|
840 @end smallexample
|
|
|
841
|
|
|
842 @item -Wampersand
|
|
|
843 @opindex @code{Wampersand}
|
|
|
844 @cindex warnings, ampersand
|
|
|
845 @cindex @code{&}
|
|
|
846 Warn about missing ampersand in continued character constants. The warning is
|
|
|
847 given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95},
|
|
|
848 @option{-std=f2003} and @option{-std=f2008}. Note: With no ampersand
|
|
|
849 given in a continued character constant, GNU Fortran assumes continuation
|
|
|
850 at the first non-comment, non-whitespace character after the ampersand
|
|
|
851 that initiated the continuation.
|
|
|
852
|
|
|
853 @item -Wargument-mismatch
|
|
|
854 @opindex @code{Wargument-mismatch}
|
|
|
855 @cindex warnings, argument mismatch
|
|
|
856 @cindex warnings, parameter mismatch
|
|
|
857 @cindex warnings, interface mismatch
|
|
|
858 Warn about type, rank, and other mismatches between formal parameters and actual
|
|
|
859 arguments to functions and subroutines. These warnings are recommended and
|
|
|
860 thus enabled by default.
|
|
|
861
|
|
|
862 @item -Warray-temporaries
|
|
|
863 @opindex @code{Warray-temporaries}
|
|
|
864 @cindex warnings, array temporaries
|
|
|
865 Warn about array temporaries generated by the compiler. The information
|
|
|
866 generated by this warning is sometimes useful in optimization, in order to
|
|
|
867 avoid such temporaries.
|
|
|
868
|
|
|
869 @item -Wc-binding-type
|
|
|
870 @opindex @code{Wc-binding-type}
|
|
|
871 @cindex warning, C binding type
|
|
|
872 Warn if the a variable might not be C interoperable. In particular, warn if
|
|
|
873 the variable has been declared using an intrinsic type with default kind
|
|
|
874 instead of using a kind parameter defined for C interoperability in the
|
|
|
875 intrinsic @code{ISO_C_Binding} module. This option is implied by
|
|
|
876 @option{-Wall}.
|
|
|
877
|
|
|
878 @item -Wcharacter-truncation
|
|
|
879 @opindex @code{Wcharacter-truncation}
|
|
|
880 @cindex warnings, character truncation
|
|
|
881 Warn when a character assignment will truncate the assigned string.
|
|
|
882
|
|
|
883 @item -Wline-truncation
|
|
|
884 @opindex @code{Wline-truncation}
|
|
|
885 @cindex warnings, line truncation
|
|
|
886 Warn when a source code line will be truncated. This option is
|
|
|
887 implied by @option{-Wall}. For free-form source code, the default is
|
|
|
888 @option{-Werror=line-truncation} such that truncations are reported as
|
|
|
889 error.
|
|
|
890
|
|
|
891 @item -Wconversion
|
|
|
892 @opindex @code{Wconversion}
|
|
|
893 @cindex warnings, conversion
|
|
|
894 @cindex conversion
|
|
|
895 Warn about implicit conversions that are likely to change the value of
|
|
|
896 the expression after conversion. Implied by @option{-Wall}.
|
|
|
897
|
|
|
898 @item -Wconversion-extra
|
|
|
899 @opindex @code{Wconversion-extra}
|
|
|
900 @cindex warnings, conversion
|
|
|
901 @cindex conversion
|
|
|
902 Warn about implicit conversions between different types and kinds. This
|
|
|
903 option does @emph{not} imply @option{-Wconversion}.
|
|
|
904
|
|
|
905 @item -Wextra
|
|
|
906 @opindex @code{Wextra}
|
|
|
907 @cindex extra warnings
|
|
|
908 @cindex warnings, extra
|
|
|
909 Enables some warning options for usages of language features which
|
|
|
910 may be problematic. This currently includes @option{-Wcompare-reals},
|
|
|
911 @option{-Wunused-parameter} and @option{-Wdo-subscript}.
|
|
|
912
|
|
|
913 @item -Wimplicit-interface
|
|
|
914 @opindex @code{Wimplicit-interface}
|
|
|
915 @cindex warnings, implicit interface
|
|
|
916 Warn if a procedure is called without an explicit interface.
|
|
|
917 Note this only checks that an explicit interface is present. It does not
|
|
|
918 check that the declared interfaces are consistent across program units.
|
|
|
919
|
|
|
920 @item -Wimplicit-procedure
|
|
|
921 @opindex @code{Wimplicit-procedure}
|
|
|
922 @cindex warnings, implicit procedure
|
|
|
923 Warn if a procedure is called that has neither an explicit interface
|
|
|
924 nor has been declared as @code{EXTERNAL}.
|
|
|
925
|
|
|
926 @item -Winteger-division
|
|
|
927 @opindex @code{Winteger-division}
|
|
|
928 @cindex warnings, integer division
|
|
|
929 @cindex warnings, division of integers
|
|
|
930 Warn if a constant integer division truncates it result.
|
|
|
931 As an example, 3/5 evaluates to 0.
|
|
|
932
|
|
|
933 @item -Wintrinsics-std
|
|
|
934 @opindex @code{Wintrinsics-std}
|
|
|
935 @cindex warnings, non-standard intrinsics
|
|
|
936 @cindex warnings, intrinsics of other standards
|
|
|
937 Warn if @command{gfortran} finds a procedure named like an intrinsic not
|
|
|
938 available in the currently selected standard (with @option{-std}) and treats
|
|
|
939 it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can
|
|
|
940 be used to never trigger this behavior and always link to the intrinsic
|
|
|
941 regardless of the selected standard.
|
|
|
942
|
|
|
943 @item -Wreal-q-constant
|
|
|
944 @opindex @code{Wreal-q-constant}
|
|
|
945 @cindex warnings, @code{q} exponent-letter
|
|
|
946 Produce a warning if a real-literal-constant contains a @code{q}
|
|
|
947 exponent-letter.
|
|
|
948
|
|
|
949 @item -Wsurprising
|
|
|
950 @opindex @code{Wsurprising}
|
|
|
951 @cindex warnings, suspicious code
|
|
|
952 Produce a warning when ``suspicious'' code constructs are encountered.
|
|
|
953 While technically legal these usually indicate that an error has been made.
|
|
|
954
|
|
|
955 This currently produces a warning under the following circumstances:
|
|
|
956
|
|
|
957 @itemize @bullet
|
|
|
958 @item
|
|
|
959 An INTEGER SELECT construct has a CASE that can never be matched as its
|
|
|
960 lower value is greater than its upper value.
|
|
|
961
|
|
|
962 @item
|
|
|
963 A LOGICAL SELECT construct has three CASE statements.
|
|
|
964
|
|
|
965 @item
|
|
|
966 A TRANSFER specifies a source that is shorter than the destination.
|
|
|
967
|
|
|
968 @item
|
|
|
969 The type of a function result is declared more than once with the same type. If
|
|
|
970 @option{-pedantic} or standard-conforming mode is enabled, this is an error.
|
|
|
971
|
|
|
972 @item
|
|
|
973 A @code{CHARACTER} variable is declared with negative length.
|
|
|
974 @end itemize
|
|
|
975
|
|
|
976 @item -Wtabs
|
|
|
977 @opindex @code{Wtabs}
|
|
|
978 @cindex warnings, tabs
|
|
|
979 @cindex tabulators
|
|
|
980 By default, tabs are accepted as whitespace, but tabs are not members
|
|
|
981 of the Fortran Character Set. For continuation lines, a tab followed
|
|
|
982 by a digit between 1 and 9 is supported. @option{-Wtabs} will cause
|
|
|
983 a warning to be issued if a tab is encountered. Note, @option{-Wtabs}
|
|
|
984 is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003},
|
|
|
985 @option{-std=f2008}, @option{-std=f2008ts} and @option{-Wall}.
|
|
|
986
|
|
|
987 @item -Wundefined-do-loop
|
|
|
988 @opindex @code{Wundefined-do-loop}
|
|
|
989 @cindex warnings, undefined do loop
|
|
|
990 Warn if a DO loop with step either 1 or -1 yields an underflow or an overflow
|
|
|
991 during iteration of an induction variable of the loop.
|
|
|
992 This option is implied by @option{-Wall}.
|
|
|
993
|
|
|
994 @item -Wunderflow
|
|
|
995 @opindex @code{Wunderflow}
|
|
|
996 @cindex warnings, underflow
|
|
|
997 @cindex underflow
|
|
|
998 Produce a warning when numerical constant expressions are
|
|
|
999 encountered, which yield an UNDERFLOW during compilation. Enabled by default.
|
|
|
1000
|
|
|
1001 @item -Wintrinsic-shadow
|
|
|
1002 @opindex @code{Wintrinsic-shadow}
|
|
|
1003 @cindex warnings, intrinsic
|
|
|
1004 @cindex intrinsic
|
|
|
1005 Warn if a user-defined procedure or module procedure has the same name as an
|
|
|
1006 intrinsic; in this case, an explicit interface or @code{EXTERNAL} or
|
|
|
1007 @code{INTRINSIC} declaration might be needed to get calls later resolved to
|
|
|
1008 the desired intrinsic/procedure. This option is implied by @option{-Wall}.
|
|
|
1009
|
|
|
1010 @item -Wuse-without-only
|
|
|
1011 @opindex @code{Wuse-without-only}
|
|
|
1012 @cindex warnings, use statements
|
|
|
1013 @cindex intrinsic
|
|
|
1014 Warn if a @code{USE} statement has no @code{ONLY} qualifier and
|
|
|
1015 thus implicitly imports all public entities of the used module.
|
|
|
1016
|
|
|
1017 @item -Wunused-dummy-argument
|
|
|
1018 @opindex @code{Wunused-dummy-argument}
|
|
|
1019 @cindex warnings, unused dummy argument
|
|
|
1020 @cindex unused dummy argument
|
|
|
1021 @cindex dummy argument, unused
|
|
|
1022 Warn about unused dummy arguments. This option is implied by @option{-Wall}.
|
|
|
1023
|
|
|
1024 @item -Wunused-parameter
|
|
|
1025 @opindex @code{Wunused-parameter}
|
|
|
1026 @cindex warnings, unused parameter
|
|
|
1027 @cindex unused parameter
|
|
|
1028 Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter},
|
|
|
1029 @command{gfortran}'s implementation of this option does not warn
|
|
|
1030 about unused dummy arguments (see @option{-Wunused-dummy-argument}),
|
|
|
1031 but about unused @code{PARAMETER} values. @option{-Wunused-parameter}
|
|
|
1032 is implied by @option{-Wextra} if also @option{-Wunused} or
|
|
|
1033 @option{-Wall} is used.
|
|
|
1034
|
|
|
1035 @item -Walign-commons
|
|
|
1036 @opindex @code{Walign-commons}
|
|
|
1037 @cindex warnings, alignment of @code{COMMON} blocks
|
|
|
1038 @cindex alignment of @code{COMMON} blocks
|
|
|
1039 By default, @command{gfortran} warns about any occasion of variables being
|
|
|
1040 padded for proper alignment inside a @code{COMMON} block. This warning can be turned
|
|
|
1041 off via @option{-Wno-align-commons}. See also @option{-falign-commons}.
|
|
|
1042
|
|
|
1043 @item -Wfunction-elimination
|
|
|
1044 @opindex @code{Wfunction-elimination}
|
|
|
1045 @cindex function elimination
|
|
|
1046 @cindex warnings, function elimination
|
|
|
1047 Warn if any calls to functions are eliminated by the optimizations
|
|
|
1048 enabled by the @option{-ffrontend-optimize} option.
|
|
|
1049
|
|
|
1050 @item -Wrealloc-lhs
|
|
|
1051 @opindex @code{Wrealloc-lhs}
|
|
|
1052 @cindex Reallocate the LHS in assignments, notification
|
|
|
1053 Warn when the compiler might insert code to for allocation or reallocation of
|
|
|
1054 an allocatable array variable of intrinsic type in intrinsic assignments. In
|
|
|
1055 hot loops, the Fortran 2003 reallocation feature may reduce the performance.
|
|
|
1056 If the array is already allocated with the correct shape, consider using a
|
|
|
1057 whole-array array-spec (e.g. @code{(:,:,:)}) for the variable on the left-hand
|
|
|
1058 side to prevent the reallocation check. Note that in some cases the warning
|
|
|
1059 is shown, even if the compiler will optimize reallocation checks away. For
|
|
|
1060 instance, when the right-hand side contains the same variable multiplied by
|
|
|
1061 a scalar. See also @option{-frealloc-lhs}.
|
|
|
1062
|
|
|
1063 @item -Wrealloc-lhs-all
|
|
|
1064 @opindex @code{Wrealloc-lhs-all}
|
|
|
1065 Warn when the compiler inserts code to for allocation or reallocation of an
|
|
|
1066 allocatable variable; this includes scalars and derived types.
|
|
|
1067
|
|
|
1068 @item -Wcompare-reals
|
|
|
1069 @opindex @code{Wcompare-reals}
|
|
|
1070 Warn when comparing real or complex types for equality or inequality.
|
|
|
1071 This option is implied by @option{-Wextra}.
|
|
|
1072
|
|
|
1073 @item -Wtarget-lifetime
|
|
|
1074 @opindex @code{Wtargt-lifetime}
|
|
|
1075 Warn if the pointer in a pointer assignment might be longer than the its
|
|
|
1076 target. This option is implied by @option{-Wall}.
|
|
|
1077
|
|
|
1078 @item -Wzerotrip
|
|
|
1079 @opindex @code{Wzerotrip}
|
|
|
1080 Warn if a @code{DO} loop is known to execute zero times at compile
|
|
|
1081 time. This option is implied by @option{-Wall}.
|
|
|
1082
|
|
|
1083 @item -Wdo-subscript
|
|
|
1084 @opindex @code{Wdo-subscript}
|
|
|
1085 Warn if an array subscript inside a DO loop could lead to an
|
|
|
1086 out-of-bounds access even if the compiler can not prove that the
|
|
|
1087 statement is actually executed, in cases like
|
|
|
1088 @smallexample
|
|
|
1089 real a(3)
|
|
|
1090 do i=1,4
|
|
|
1091 if (condition(i)) then
|
|
|
1092 a(i) = 1.2
|
|
|
1093 end if
|
|
|
1094 end do
|
|
|
1095 @end smallexample
|
|
|
1096 This option is implied by @option{-Wextra}.
|
|
|
1097
|
|
|
1098 @item -Werror
|
|
|
1099 @opindex @code{Werror}
|
|
|
1100 @cindex warnings, to errors
|
|
|
1101 Turns all warnings into errors.
|
|
|
1102 @end table
|
|
|
1103
|
|
|
1104 @xref{Warning Options,,Options to Request or Suppress Errors and
|
|
|
1105 Warnings, gcc,Using the GNU Compiler Collection (GCC)}, for information on
|
|
|
1106 more options offered by the GBE shared by @command{gfortran}, @command{gcc}
|
|
|
1107 and other GNU compilers.
|
|
|
1108
|
|
|
1109 Some of these have no effect when compiling programs written in Fortran.
|
|
|
1110
|
|
|
1111 @node Debugging Options
|
|
|
1112 @section Options for debugging your program or GNU Fortran
|
|
|
1113 @cindex options, debugging
|
|
|
1114 @cindex debugging information options
|
|
|
1115
|
|
|
1116 GNU Fortran has various special options that are used for debugging
|
|
|
1117 either your program or the GNU Fortran compiler.
|
|
|
1118
|
|
|
1119 @table @gcctabopt
|
|
|
1120 @item -fdump-fortran-original
|
|
|
1121 @opindex @code{fdump-fortran-original}
|
|
|
1122 Output the internal parse tree after translating the source program
|
|
|
1123 into internal representation. This option is mostly useful for
|
|
|
1124 debugging the GNU Fortran compiler itself. The output generated by
|
|
|
1125 this option might change between releases. This option may also
|
|
|
1126 generate internal compiler errors for features which have only
|
|
|
1127 recently been added.
|
|
|
1128
|
|
|
1129 @item -fdump-fortran-optimized
|
|
|
1130 @opindex @code{fdump-fortran-optimized}
|
|
|
1131 Output the parse tree after front-end optimization. Mostly useful for
|
|
|
1132 debugging the GNU Fortran compiler itself. The output generated by
|
|
|
1133 this option might change between releases. This option may also
|
|
|
1134 generate internal compiler errors for features which have only
|
|
|
1135 recently been added.
|
|
|
1136
|
|
|
1137 @item -fdump-parse-tree
|
|
|
1138 @opindex @code{fdump-parse-tree}
|
|
|
1139 Output the internal parse tree after translating the source program
|
|
|
1140 into internal representation. Mostly useful for debugging the GNU
|
|
|
1141 Fortran compiler itself. The output generated by this option might
|
|
|
1142 change between releases. This option may also generate internal
|
|
|
1143 compiler errors for features which have only recently been added. This
|
|
|
1144 option is deprecated; use @code{-fdump-fortran-original} instead.
|
|
|
1145
|
|
|
1146 @item -ffpe-trap=@var{list}
|
|
|
1147 @opindex @code{ffpe-trap=}@var{list}
|
|
|
1148 Specify a list of floating point exception traps to enable. On most
|
|
|
1149 systems, if a floating point exception occurs and the trap for that
|
|
|
1150 exception is enabled, a SIGFPE signal will be sent and the program
|
|
|
1151 being aborted, producing a core file useful for debugging. @var{list}
|
|
|
1152 is a (possibly empty) comma-separated list of the following
|
|
|
1153 exceptions: @samp{invalid} (invalid floating point operation, such as
|
|
|
1154 @code{SQRT(-1.0)}), @samp{zero} (division by zero), @samp{overflow}
|
|
|
1155 (overflow in a floating point operation), @samp{underflow} (underflow
|
|
|
1156 in a floating point operation), @samp{inexact} (loss of precision
|
|
|
1157 during operation), and @samp{denormal} (operation performed on a
|
|
|
1158 denormal value). The first five exceptions correspond to the five
|
|
|
1159 IEEE 754 exceptions, whereas the last one (@samp{denormal}) is not
|
|
|
1160 part of the IEEE 754 standard but is available on some common
|
|
|
1161 architectures such as x86.
|
|
|
1162
|
|
|
1163 The first three exceptions (@samp{invalid}, @samp{zero}, and
|
|
|
1164 @samp{overflow}) often indicate serious errors, and unless the program
|
|
|
1165 has provisions for dealing with these exceptions, enabling traps for
|
|
|
1166 these three exceptions is probably a good idea.
|
|
|
1167
|
|
|
1168 Many, if not most, floating point operations incur loss of precision
|
|
|
1169 due to rounding, and hence the @code{ffpe-trap=inexact} is likely to
|
|
|
1170 be uninteresting in practice.
|
|
|
1171
|
|
|
1172 By default no exception traps are enabled.
|
|
|
1173
|
|
|
1174 @item -ffpe-summary=@var{list}
|
|
|
1175 @opindex @code{ffpe-summary=}@var{list}
|
|
|
1176 Specify a list of floating-point exceptions, whose flag status is printed
|
|
|
1177 to @code{ERROR_UNIT} when invoking @code{STOP} and @code{ERROR STOP}.
|
|
|
1178 @var{list} can be either @samp{none}, @samp{all} or a comma-separated list
|
|
|
1179 of the following exceptions: @samp{invalid}, @samp{zero}, @samp{overflow},
|
|
|
1180 @samp{underflow}, @samp{inexact} and @samp{denormal}. (See
|
|
|
1181 @option{-ffpe-trap} for a description of the exceptions.)
|
|
|
1182
|
|
|
1183 By default, a summary for all exceptions but @samp{inexact} is shown.
|
|
|
1184
|
|
|
1185 @item -fno-backtrace
|
|
|
1186 @opindex @code{fno-backtrace}
|
|
|
1187 @cindex backtrace
|
|
|
1188 @cindex trace
|
|
|
1189 When a serious runtime error is encountered or a deadly signal is
|
|
|
1190 emitted (segmentation fault, illegal instruction, bus error,
|
|
|
1191 floating-point exception, and the other POSIX signals that have the
|
|
|
1192 action @samp{core}), the Fortran runtime library tries to output a
|
|
|
1193 backtrace of the error. @code{-fno-backtrace} disables the backtrace
|
|
|
1194 generation. This option only has influence for compilation of the
|
|
|
1195 Fortran main program.
|
|
|
1196
|
|
|
1197 @end table
|
|
|
1198
|
|
|
1199 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
|
|
|
1200 gcc,Using the GNU Compiler Collection (GCC)}, for more information on
|
|
|
1201 debugging options.
|
|
|
1202
|
|
|
1203 @node Directory Options
|
|
|
1204 @section Options for directory search
|
|
|
1205 @cindex directory, options
|
|
|
1206 @cindex options, directory search
|
|
|
1207 @cindex search path
|
|
|
1208 @cindex @code{INCLUDE} directive
|
|
|
1209 @cindex directive, @code{INCLUDE}
|
|
|
1210 These options affect how GNU Fortran searches
|
|
|
1211 for files specified by the @code{INCLUDE} directive and where it searches
|
|
|
1212 for previously compiled modules.
|
|
|
1213
|
|
|
1214 It also affects the search paths used by @command{cpp} when used to preprocess
|
|
|
1215 Fortran source.
|
|
|
1216
|
|
|
1217 @table @gcctabopt
|
|
|
1218 @item -I@var{dir}
|
|
|
1219 @opindex @code{I}@var{dir}
|
|
|
1220 @cindex directory, search paths for inclusion
|
|
|
1221 @cindex inclusion, directory search paths for
|
|
|
1222 @cindex search paths, for included files
|
|
|
1223 @cindex paths, search
|
|
|
1224 @cindex module search path
|
|
|
1225 These affect interpretation of the @code{INCLUDE} directive
|
|
|
1226 (as well as of the @code{#include} directive of the @command{cpp}
|
|
|
1227 preprocessor).
|
|
|
1228
|
|
|
1229 Also note that the general behavior of @option{-I} and
|
|
|
1230 @code{INCLUDE} is pretty much the same as of @option{-I} with
|
|
|
1231 @code{#include} in the @command{cpp} preprocessor, with regard to
|
|
|
1232 looking for @file{header.gcc} files and other such things.
|
|
|
1233
|
|
|
1234 This path is also used to search for @file{.mod} files when previously
|
|
|
1235 compiled modules are required by a @code{USE} statement.
|
|
|
1236
|
|
|
1237 @xref{Directory Options,,Options for Directory Search,
|
|
|
1238 gcc,Using the GNU Compiler Collection (GCC)}, for information on the
|
|
|
1239 @option{-I} option.
|
|
|
1240
|
|
|
1241 @item -J@var{dir}
|
|
|
1242 @opindex @code{J}@var{dir}
|
|
|
1243 @opindex @code{M}@var{dir}
|
|
|
1244 @cindex paths, search
|
|
|
1245 @cindex module search path
|
|
|
1246 This option specifies where to put @file{.mod} files for compiled modules.
|
|
|
1247 It is also added to the list of directories to searched by an @code{USE}
|
|
|
1248 statement.
|
|
|
1249
|
|
|
1250 The default is the current directory.
|
|
|
1251
|
|
|
1252 @item -fintrinsic-modules-path @var{dir}
|
|
|
1253 @opindex @code{fintrinsic-modules-path} @var{dir}
|
|
|
1254 @cindex paths, search
|
|
|
1255 @cindex module search path
|
|
|
1256 This option specifies the location of pre-compiled intrinsic modules, if
|
|
|
1257 they are not in the default location expected by the compiler.
|
|
|
1258 @end table
|
|
|
1259
|
|
|
1260 @node Link Options
|
|
|
1261 @section Influencing the linking step
|
|
|
1262 @cindex options, linking
|
|
|
1263 @cindex linking, static
|
|
|
1264
|
|
|
1265 These options come into play when the compiler links object files into an
|
|
|
1266 executable output file. They are meaningless if the compiler is not doing
|
|
|
1267 a link step.
|
|
|
1268
|
|
|
1269 @table @gcctabopt
|
|
|
1270 @item -static-libgfortran
|
|
|
1271 @opindex @code{static-libgfortran}
|
|
|
1272 On systems that provide @file{libgfortran} as a shared and a static
|
|
|
1273 library, this option forces the use of the static version. If no
|
|
|
1274 shared version of @file{libgfortran} was built when the compiler was
|
|
|
1275 configured, this option has no effect.
|
|
|
1276 @end table
|
|
|
1277
|
|
|
1278
|
|
|
1279 @node Runtime Options
|
|
|
1280 @section Influencing runtime behavior
|
|
|
1281 @cindex options, runtime
|
|
|
1282
|
|
|
1283 These options affect the runtime behavior of programs compiled with GNU Fortran.
|
|
|
1284
|
|
|
1285 @table @gcctabopt
|
|
|
1286 @item -fconvert=@var{conversion}
|
|
|
1287 @opindex @code{fconvert=}@var{conversion}
|
|
|
1288 Specify the representation of data for unformatted files. Valid
|
|
|
1289 values for conversion are: @samp{native}, the default; @samp{swap},
|
|
|
1290 swap between big- and little-endian; @samp{big-endian}, use big-endian
|
|
|
1291 representation for unformatted files; @samp{little-endian}, use little-endian
|
|
|
1292 representation for unformatted files.
|
|
|
1293
|
|
|
1294 @emph{This option has an effect only when used in the main program.
|
|
|
1295 The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment
|
|
|
1296 variable override the default specified by @option{-fconvert}.}
|
|
|
1297
|
|
|
1298 @item -frecord-marker=@var{length}
|
|
|
1299 @opindex @code{frecord-marker=}@var{length}
|
|
|
1300 Specify the length of record markers for unformatted files.
|
|
|
1301 Valid values for @var{length} are 4 and 8. Default is 4.
|
|
|
1302 @emph{This is different from previous versions of @command{gfortran}},
|
|
|
1303 which specified a default record marker length of 8 on most
|
|
|
1304 systems. If you want to read or write files compatible
|
|
|
1305 with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}.
|
|
|
1306
|
|
|
1307 @item -fmax-subrecord-length=@var{length}
|
|
|
1308 @opindex @code{fmax-subrecord-length=}@var{length}
|
|
|
1309 Specify the maximum length for a subrecord. The maximum permitted
|
|
|
1310 value for length is 2147483639, which is also the default. Only
|
|
|
1311 really useful for use by the gfortran testsuite.
|
|
|
1312
|
|
|
1313 @item -fsign-zero
|
|
|
1314 @opindex @code{fsign-zero}
|
|
|
1315 When enabled, floating point numbers of value zero with the sign bit set
|
|
|
1316 are written as negative number in formatted output and treated as
|
|
|
1317 negative in the @code{SIGN} intrinsic. @option{-fno-sign-zero} does not
|
|
|
1318 print the negative sign of zero values (or values rounded to zero for I/O)
|
|
|
1319 and regards zero as positive number in the @code{SIGN} intrinsic for
|
|
|
1320 compatibility with Fortran 77. The default is @option{-fsign-zero}.
|
|
|
1321 @end table
|
|
|
1322
|
|
|
1323 @node Code Gen Options
|
|
|
1324 @section Options for code generation conventions
|
|
|
1325 @cindex code generation, conventions
|
|
|
1326 @cindex options, code generation
|
|
|
1327 @cindex options, run-time
|
|
|
1328
|
|
|
1329 These machine-independent options control the interface conventions
|
|
|
1330 used in code generation.
|
|
|
1331
|
|
|
1332 Most of them have both positive and negative forms; the negative form
|
|
|
1333 of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
|
|
|
1334 one of the forms is listed---the one which is not the default. You
|
|
|
1335 can figure out the other form by either removing @option{no-} or adding
|
|
|
1336 it.
|
|
|
1337
|
|
|
1338 @table @gcctabopt
|
|
|
1339 @item -fno-automatic
|
|
|
1340 @opindex @code{fno-automatic}
|
|
|
1341 @cindex @code{SAVE} statement
|
|
|
1342 @cindex statement, @code{SAVE}
|
|
|
1343 Treat each program unit (except those marked as RECURSIVE) as if the
|
|
|
1344 @code{SAVE} statement were specified for every local variable and array
|
|
|
1345 referenced in it. Does not affect common blocks. (Some Fortran compilers
|
|
|
1346 provide this option under the name @option{-static} or @option{-save}.)
|
|
|
1347 The default, which is @option{-fautomatic}, uses the stack for local
|
|
|
1348 variables smaller than the value given by @option{-fmax-stack-var-size}.
|
|
|
1349 Use the option @option{-frecursive} to use no static memory.
|
|
|
1350
|
|
|
1351 @item -ff2c
|
|
|
1352 @opindex ff2c
|
|
|
1353 @cindex calling convention
|
|
|
1354 @cindex @command{f2c} calling convention
|
|
|
1355 @cindex @command{g77} calling convention
|
|
|
1356 @cindex libf2c calling convention
|
|
|
1357 Generate code designed to be compatible with code generated
|
|
|
1358 by @command{g77} and @command{f2c}.
|
|
|
1359
|
|
|
1360 The calling conventions used by @command{g77} (originally implemented
|
|
|
1361 in @command{f2c}) require functions that return type
|
|
|
1362 default @code{REAL} to actually return the C type @code{double}, and
|
|
|
1363 functions that return type @code{COMPLEX} to return the values via an
|
|
|
1364 extra argument in the calling sequence that points to where to
|
|
|
1365 store the return value. Under the default GNU calling conventions, such
|
|
|
1366 functions simply return their results as they would in GNU
|
|
|
1367 C---default @code{REAL} functions return the C type @code{float}, and
|
|
|
1368 @code{COMPLEX} functions return the GNU C type @code{complex}.
|
|
|
1369 Additionally, this option implies the @option{-fsecond-underscore}
|
|
|
1370 option, unless @option{-fno-second-underscore} is explicitly requested.
|
|
|
1371
|
|
|
1372 This does not affect the generation of code that interfaces with
|
|
|
1373 the @command{libgfortran} library.
|
|
|
1374
|
|
|
1375 @emph{Caution:} It is not a good idea to mix Fortran code compiled with
|
|
|
1376 @option{-ff2c} with code compiled with the default @option{-fno-f2c}
|
|
|
1377 calling conventions as, calling @code{COMPLEX} or default @code{REAL}
|
|
|
1378 functions between program parts which were compiled with different
|
|
|
1379 calling conventions will break at execution time.
|
|
|
1380
|
|
|
1381 @emph{Caution:} This will break code which passes intrinsic functions
|
|
|
1382 of type default @code{REAL} or @code{COMPLEX} as actual arguments, as
|
|
|
1383 the library implementations use the @option{-fno-f2c} calling conventions.
|
|
|
1384
|
|
|
1385 @item -fno-underscoring
|
|
|
1386 @opindex @code{fno-underscoring}
|
|
|
1387 @cindex underscore
|
|
|
1388 @cindex symbol names, underscores
|
|
|
1389 @cindex transforming symbol names
|
|
|
1390 @cindex symbol names, transforming
|
|
|
1391 Do not transform names of entities specified in the Fortran
|
|
|
1392 source file by appending underscores to them.
|
|
|
1393
|
|
|
1394 With @option{-funderscoring} in effect, GNU Fortran appends one
|
|
|
1395 underscore to external names with no underscores. This is done to ensure
|
|
|
1396 compatibility with code produced by many UNIX Fortran compilers.
|
|
|
1397
|
|
|
1398 @emph{Caution}: The default behavior of GNU Fortran is
|
|
|
1399 incompatible with @command{f2c} and @command{g77}, please use the
|
|
|
1400 @option{-ff2c} option if you want object files compiled with
|
|
|
1401 GNU Fortran to be compatible with object code created with these
|
|
|
1402 tools.
|
|
|
1403
|
|
|
1404 Use of @option{-fno-underscoring} is not recommended unless you are
|
|
|
1405 experimenting with issues such as integration of GNU Fortran into
|
|
|
1406 existing system environments (vis-@`{a}-vis existing libraries, tools,
|
|
|
1407 and so on).
|
|
|
1408
|
|
|
1409 For example, with @option{-funderscoring}, and assuming that @code{j()} and
|
|
|
1410 @code{max_count()} are external functions while @code{my_var} and
|
|
|
1411 @code{lvar} are local variables, a statement like
|
|
|
1412 @smallexample
|
|
|
1413 I = J() + MAX_COUNT (MY_VAR, LVAR)
|
|
|
1414 @end smallexample
|
|
|
1415 @noindent
|
|
|
1416 is implemented as something akin to:
|
|
|
1417 @smallexample
|
|
|
1418 i = j_() + max_count__(&my_var__, &lvar);
|
|
|
1419 @end smallexample
|
|
|
1420
|
|
|
1421 With @option{-fno-underscoring}, the same statement is implemented as:
|
|
|
1422
|
|
|
1423 @smallexample
|
|
|
1424 i = j() + max_count(&my_var, &lvar);
|
|
|
1425 @end smallexample
|
|
|
1426
|
|
|
1427 Use of @option{-fno-underscoring} allows direct specification of
|
|
|
1428 user-defined names while debugging and when interfacing GNU Fortran
|
|
|
1429 code with other languages.
|
|
|
1430
|
|
|
1431 Note that just because the names match does @emph{not} mean that the
|
|
|
1432 interface implemented by GNU Fortran for an external name matches the
|
|
|
1433 interface implemented by some other language for that same name.
|
|
|
1434 That is, getting code produced by GNU Fortran to link to code produced
|
|
|
1435 by some other compiler using this or any other method can be only a
|
|
|
1436 small part of the overall solution---getting the code generated by
|
|
|
1437 both compilers to agree on issues other than naming can require
|
|
|
1438 significant effort, and, unlike naming disagreements, linkers normally
|
|
|
1439 cannot detect disagreements in these other areas.
|
|
|
1440
|
|
|
1441 Also, note that with @option{-fno-underscoring}, the lack of appended
|
|
|
1442 underscores introduces the very real possibility that a user-defined
|
|
|
1443 external name will conflict with a name in a system library, which
|
|
|
1444 could make finding unresolved-reference bugs quite difficult in some
|
|
|
1445 cases---they might occur at program run time, and show up only as
|
|
|
1446 buggy behavior at run time.
|
|
|
1447
|
|
|
1448 In future versions of GNU Fortran we hope to improve naming and linking
|
|
|
1449 issues so that debugging always involves using the names as they appear
|
|
|
1450 in the source, even if the names as seen by the linker are mangled to
|
|
|
1451 prevent accidental linking between procedures with incompatible
|
|
|
1452 interfaces.
|
|
|
1453
|
|
|
1454 @item -fsecond-underscore
|
|
|
1455 @opindex @code{fsecond-underscore}
|
|
|
1456 @cindex underscore
|
|
|
1457 @cindex symbol names, underscores
|
|
|
1458 @cindex transforming symbol names
|
|
|
1459 @cindex symbol names, transforming
|
|
|
1460 @cindex @command{f2c} calling convention
|
|
|
1461 @cindex @command{g77} calling convention
|
|
|
1462 @cindex libf2c calling convention
|
|
|
1463 By default, GNU Fortran appends an underscore to external
|
|
|
1464 names. If this option is used GNU Fortran appends two
|
|
|
1465 underscores to names with underscores and one underscore to external names
|
|
|
1466 with no underscores. GNU Fortran also appends two underscores to
|
|
|
1467 internal names with underscores to avoid naming collisions with external
|
|
|
1468 names.
|
|
|
1469
|
|
|
1470 This option has no effect if @option{-fno-underscoring} is
|
|
|
1471 in effect. It is implied by the @option{-ff2c} option.
|
|
|
1472
|
|
|
1473 Otherwise, with this option, an external name such as @code{MAX_COUNT}
|
|
|
1474 is implemented as a reference to the link-time external symbol
|
|
|
1475 @code{max_count__}, instead of @code{max_count_}. This is required
|
|
|
1476 for compatibility with @command{g77} and @command{f2c}, and is implied
|
|
|
1477 by use of the @option{-ff2c} option.
|
|
|
1478
|
|
|
1479 @item -fcoarray=@var{<keyword>}
|
|
|
1480 @opindex @code{fcoarray}
|
|
|
1481 @cindex coarrays
|
|
|
1482
|
|
|
1483 @table @asis
|
|
|
1484 @item @samp{none}
|
|
|
1485 Disable coarray support; using coarray declarations and image-control
|
|
|
1486 statements will produce a compile-time error. (Default)
|
|
|
1487
|
|
|
1488 @item @samp{single}
|
|
|
1489 Single-image mode, i.e. @code{num_images()} is always one.
|
|
|
1490
|
|
|
1491 @item @samp{lib}
|
|
|
1492 Library-based coarray parallelization; a suitable GNU Fortran coarray
|
|
|
1493 library needs to be linked.
|
|
|
1494 @end table
|
|
|
1495
|
|
|
1496
|
|
|
1497 @item -fcheck=@var{<keyword>}
|
|
|
1498 @opindex @code{fcheck}
|
|
|
1499 @cindex array, bounds checking
|
|
|
1500 @cindex bounds checking
|
|
|
1501 @cindex pointer checking
|
|
|
1502 @cindex memory checking
|
|
|
1503 @cindex range checking
|
|
|
1504 @cindex subscript checking
|
|
|
1505 @cindex checking subscripts
|
|
|
1506 @cindex run-time checking
|
|
|
1507 @cindex checking array temporaries
|
|
|
1508
|
|
|
1509 Enable the generation of run-time checks; the argument shall be
|
|
|
1510 a comma-delimited list of the following keywords. Prefixing a check with
|
|
|
1511 @option{no-} disables it if it was activated by a previous specification.
|
|
|
1512
|
|
|
1513 @table @asis
|
|
|
1514 @item @samp{all}
|
|
|
1515 Enable all run-time test of @option{-fcheck}.
|
|
|
1516
|
|
|
1517 @item @samp{array-temps}
|
|
|
1518 Warns at run time when for passing an actual argument a temporary array
|
|
|
1519 had to be generated. The information generated by this warning is
|
|
|
1520 sometimes useful in optimization, in order to avoid such temporaries.
|
|
|
1521
|
|
|
1522 Note: The warning is only printed once per location.
|
|
|
1523
|
|
|
1524 @item @samp{bounds}
|
|
|
1525 Enable generation of run-time checks for array subscripts
|
|
|
1526 and against the declared minimum and maximum values. It also
|
|
|
1527 checks array indices for assumed and deferred
|
|
|
1528 shape arrays against the actual allocated bounds and ensures that all string
|
|
|
1529 lengths are equal for character array constructors without an explicit
|
|
|
1530 typespec.
|
|
|
1531
|
|
|
1532 Some checks require that @option{-fcheck=bounds} is set for
|
|
|
1533 the compilation of the main program.
|
|
|
1534
|
|
|
1535 Note: In the future this may also include other forms of checking, e.g.,
|
|
|
1536 checking substring references.
|
|
|
1537
|
|
|
1538 @item @samp{do}
|
|
|
1539 Enable generation of run-time checks for invalid modification of loop
|
|
|
1540 iteration variables.
|
|
|
1541
|
|
|
1542 @item @samp{mem}
|
|
|
1543 Enable generation of run-time checks for memory allocation.
|
|
|
1544 Note: This option does not affect explicit allocations using the
|
|
|
1545 @code{ALLOCATE} statement, which will be always checked.
|
|
|
1546
|
|
|
1547 @item @samp{pointer}
|
|
|
1548 Enable generation of run-time checks for pointers and allocatables.
|
|
|
1549
|
|
|
1550 @item @samp{recursion}
|
|
|
1551 Enable generation of run-time checks for recursively called subroutines and
|
|
|
1552 functions which are not marked as recursive. See also @option{-frecursive}.
|
|
|
1553 Note: This check does not work for OpenMP programs and is disabled if used
|
|
|
1554 together with @option{-frecursive} and @option{-fopenmp}.
|
|
|
1555 @end table
|
|
|
1556
|
|
|
1557 Example: Assuming you have a file @file{foo.f90}, the command
|
|
|
1558 @smallexample
|
|
|
1559 gfortran -fcheck=all,no-array-temps foo.f90
|
|
|
1560 @end smallexample
|
|
|
1561 will compile the file with all checks enabled as specified above except
|
|
|
1562 warnings for generated array temporaries.
|
|
|
1563
|
|
|
1564
|
|
|
1565 @item -fbounds-check
|
|
|
1566 @opindex @code{fbounds-check}
|
|
|
1567 @c Note: This option is also referred in gcc's manpage
|
|
|
1568 Deprecated alias for @option{-fcheck=bounds}.
|
|
|
1569
|
|
|
1570 @item -fcheck-array-temporaries
|
|
|
1571 @opindex @code{fcheck-array-temporaries}
|
|
|
1572 Deprecated alias for @option{-fcheck=array-temps}.
|
|
|
1573
|
|
|
1574 @item -fmax-array-constructor=@var{n}
|
|
|
1575 @opindex @code{fmax-array-constructor}
|
|
|
1576 This option can be used to increase the upper limit permitted in
|
|
|
1577 array constructors. The code below requires this option to expand
|
|
|
1578 the array at compile time.
|
|
|
1579
|
|
|
1580 @smallexample
|
|
|
1581 program test
|
|
|
1582 implicit none
|
|
|
1583 integer j
|
|
|
1584 integer, parameter :: n = 100000
|
|
|
1585 integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)
|
|
|
1586 print '(10(I0,1X))', i
|
|
|
1587 end program test
|
|
|
1588 @end smallexample
|
|
|
1589
|
|
|
1590 @emph{Caution: This option can lead to long compile times and excessively
|
|
|
1591 large object files.}
|
|
|
1592
|
|
|
1593 The default value for @var{n} is 65535.
|
|
|
1594
|
|
|
1595
|
|
|
1596 @item -fmax-stack-var-size=@var{n}
|
|
|
1597 @opindex @code{fmax-stack-var-size}
|
|
|
1598 This option specifies the size in bytes of the largest array that will be put
|
|
|
1599 on the stack; if the size is exceeded static memory is used (except in
|
|
|
1600 procedures marked as RECURSIVE). Use the option @option{-frecursive} to
|
|
|
1601 allow for recursive procedures which do not have a RECURSIVE attribute or
|
|
|
1602 for parallel programs. Use @option{-fno-automatic} to never use the stack.
|
|
|
1603
|
|
|
1604 This option currently only affects local arrays declared with constant
|
|
|
1605 bounds, and may not apply to all character variables.
|
|
|
1606 Future versions of GNU Fortran may improve this behavior.
|
|
|
1607
|
|
|
1608 The default value for @var{n} is 32768.
|
|
|
1609
|
|
|
1610 @item -fstack-arrays
|
|
|
1611 @opindex @code{fstack-arrays}
|
|
|
1612 Adding this option will make the Fortran compiler put all arrays of
|
|
|
1613 unknown size and array temporaries onto stack memory. If your program uses very
|
|
|
1614 large local arrays it is possible that you will have to extend your runtime
|
|
|
1615 limits for stack memory on some operating systems. This flag is enabled
|
|
|
1616 by default at optimization level @option{-Ofast} unless
|
|
|
1617 @option{-fmax-stack-var-size} is specified.
|
|
|
1618
|
|
|
1619 @item -fpack-derived
|
|
|
1620 @opindex @code{fpack-derived}
|
|
|
1621 @cindex structure packing
|
|
|
1622 This option tells GNU Fortran to pack derived type members as closely as
|
|
|
1623 possible. Code compiled with this option is likely to be incompatible
|
|
|
1624 with code compiled without this option, and may execute slower.
|
|
|
1625
|
|
|
1626 @item -frepack-arrays
|
|
|
1627 @opindex @code{frepack-arrays}
|
|
|
1628 @cindex repacking arrays
|
|
|
1629 In some circumstances GNU Fortran may pass assumed shape array
|
|
|
1630 sections via a descriptor describing a noncontiguous area of memory.
|
|
|
1631 This option adds code to the function prologue to repack the data into
|
|
|
1632 a contiguous block at runtime.
|
|
|
1633
|
|
|
1634 This should result in faster accesses to the array. However it can introduce
|
|
|
1635 significant overhead to the function call, especially when the passed data
|
|
|
1636 is noncontiguous.
|
|
|
1637
|
|
|
1638 @item -fshort-enums
|
|
|
1639 @opindex @code{fshort-enums}
|
|
|
1640 This option is provided for interoperability with C code that was
|
|
|
1641 compiled with the @option{-fshort-enums} option. It will make
|
|
|
1642 GNU Fortran choose the smallest @code{INTEGER} kind a given
|
|
|
1643 enumerator set will fit in, and give all its enumerators this kind.
|
|
|
1644
|
|
|
1645 @item -fexternal-blas
|
|
|
1646 @opindex @code{fexternal-blas}
|
|
|
1647 This option will make @command{gfortran} generate calls to BLAS functions
|
|
|
1648 for some matrix operations like @code{MATMUL}, instead of using our own
|
|
|
1649 algorithms, if the size of the matrices involved is larger than a given
|
|
|
1650 limit (see @option{-fblas-matmul-limit}). This may be profitable if an
|
|
|
1651 optimized vendor BLAS library is available. The BLAS library will have
|
|
|
1652 to be specified at link time.
|
|
|
1653
|
|
|
1654 @item -fblas-matmul-limit=@var{n}
|
|
|
1655 @opindex @code{fblas-matmul-limit}
|
|
|
1656 Only significant when @option{-fexternal-blas} is in effect.
|
|
|
1657 Matrix multiplication of matrices with size larger than (or equal to) @var{n}
|
|
|
1658 will be performed by calls to BLAS functions, while others will be
|
|
|
1659 handled by @command{gfortran} internal algorithms. If the matrices
|
|
|
1660 involved are not square, the size comparison is performed using the
|
|
|
1661 geometric mean of the dimensions of the argument and result matrices.
|
|
|
1662
|
|
|
1663 The default value for @var{n} is 30.
|
|
|
1664
|
|
|
1665 @item -finline-matmul-limit=@var{n}
|
|
|
1666 @opindex @code{finline-matmul-limit}
|
|
|
1667 When front-end optimiztion is active, some calls to the @code{MATMUL}
|
|
|
1668 intrinsic function will be inlined. This may result in code size
|
|
|
1669 increase if the size of the matrix cannot be determined at compile
|
|
|
1670 time, as code for both cases is generated. Setting
|
|
|
1671 @code{-finline-matmul-limit=0} will disable inlining in all cases.
|
|
|
1672 Setting this option with a value of @var{n} will produce inline code
|
|
|
1673 for matrices with size up to @var{n}. If the matrices involved are not
|
|
|
1674 square, the size comparison is performed using the geometric mean of
|
|
|
1675 the dimensions of the argument and result matrices.
|
|
|
1676
|
|
|
1677 The default value for @var{n} is 30. The @code{-fblas-matmul-limit}
|
|
|
1678 can be used to change this value.
|
|
|
1679
|
|
|
1680 @item -frecursive
|
|
|
1681 @opindex @code{frecursive}
|
|
|
1682 Allow indirect recursion by forcing all local arrays to be allocated
|
|
|
1683 on the stack. This flag cannot be used together with
|
|
|
1684 @option{-fmax-stack-var-size=} or @option{-fno-automatic}.
|
|
|
1685
|
|
|
1686 @item -finit-local-zero
|
|
|
1687 @itemx -finit-derived
|
|
|
1688 @itemx -finit-integer=@var{n}
|
|
|
1689 @itemx -finit-real=@var{<zero|inf|-inf|nan|snan>}
|
|
|
1690 @itemx -finit-logical=@var{<true|false>}
|
|
|
1691 @itemx -finit-character=@var{n}
|
|
|
1692 @opindex @code{finit-local-zero}
|
|
|
1693 @opindex @code{finit-derived}
|
|
|
1694 @opindex @code{finit-integer}
|
|
|
1695 @opindex @code{finit-real}
|
|
|
1696 @opindex @code{finit-logical}
|
|
|
1697 @opindex @code{finit-character}
|
|
|
1698 The @option{-finit-local-zero} option instructs the compiler to
|
|
|
1699 initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX}
|
|
|
1700 variables to zero, @code{LOGICAL} variables to false, and
|
|
|
1701 @code{CHARACTER} variables to a string of null bytes. Finer-grained
|
|
|
1702 initialization options are provided by the
|
|
|
1703 @option{-finit-integer=@var{n}},
|
|
|
1704 @option{-finit-real=@var{<zero|inf|-inf|nan|snan>}} (which also initializes
|
|
|
1705 the real and imaginary parts of local @code{COMPLEX} variables),
|
|
|
1706 @option{-finit-logical=@var{<true|false>}}, and
|
|
|
1707 @option{-finit-character=@var{n}} (where @var{n} is an ASCII character
|
|
|
1708 value) options. Components of derived type variables will be initialized
|
|
|
1709 according to these flags only with @option{-finit-derived}. These options do
|
|
|
1710 not initialize
|
|
|
1711 @itemize @bullet
|
|
|
1712 @item
|
|
|
1713 objects with the POINTER attribute
|
|
|
1714 @item
|
|
|
1715 allocatable arrays
|
|
|
1716 @item
|
|
|
1717 variables that appear in an @code{EQUIVALENCE} statement.
|
|
|
1718 @end itemize
|
|
|
1719 (These limitations may be removed in future releases).
|
|
|
1720
|
|
|
1721 Note that the @option{-finit-real=nan} option initializes @code{REAL}
|
|
|
1722 and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN
|
|
|
1723 use @option{-finit-real=snan}; note, however, that compile-time
|
|
|
1724 optimizations may convert them into quiet NaN and that trapping
|
|
|
1725 needs to be enabled (e.g. via @option{-ffpe-trap}).
|
|
|
1726
|
|
|
1727 Finally, note that enabling any of the @option{-finit-*} options will
|
|
|
1728 silence warnings that would have been emitted by @option{-Wuninitialized}
|
|
|
1729 for the affected local variables.
|
|
|
1730
|
|
|
1731 @item -falign-commons
|
|
|
1732 @opindex @code{falign-commons}
|
|
|
1733 @cindex alignment of @code{COMMON} blocks
|
|
|
1734 By default, @command{gfortran} enforces proper alignment of all variables in a
|
|
|
1735 @code{COMMON} block by padding them as needed. On certain platforms this is mandatory,
|
|
|
1736 on others it increases performance. If a @code{COMMON} block is not declared with
|
|
|
1737 consistent data types everywhere, this padding can cause trouble, and
|
|
|
1738 @option{-fno-align-commons} can be used to disable automatic alignment. The
|
|
|
1739 same form of this option should be used for all files that share a @code{COMMON} block.
|
|
|
1740 To avoid potential alignment issues in @code{COMMON} blocks, it is recommended to order
|
|
|
1741 objects from largest to smallest.
|
|
|
1742
|
|
|
1743 @item -fno-protect-parens
|
|
|
1744 @opindex @code{fno-protect-parens}
|
|
|
1745 @cindex re-association of parenthesized expressions
|
|
|
1746 By default the parentheses in expression are honored for all optimization
|
|
|
1747 levels such that the compiler does not do any re-association. Using
|
|
|
1748 @option{-fno-protect-parens} allows the compiler to reorder @code{REAL} and
|
|
|
1749 @code{COMPLEX} expressions to produce faster code. Note that for the re-association
|
|
|
1750 optimization @option{-fno-signed-zeros} and @option{-fno-trapping-math}
|
|
|
1751 need to be in effect. The parentheses protection is enabled by default, unless
|
|
|
1752 @option{-Ofast} is given.
|
|
|
1753
|
|
|
1754 @item -frealloc-lhs
|
|
|
1755 @opindex @code{frealloc-lhs}
|
|
|
1756 @cindex Reallocate the LHS in assignments
|
|
|
1757 An allocatable left-hand side of an intrinsic assignment is automatically
|
|
|
1758 (re)allocated if it is either unallocated or has a different shape. The
|
|
|
1759 option is enabled by default except when @option{-std=f95} is given. See
|
|
|
1760 also @option{-Wrealloc-lhs}.
|
|
|
1761
|
|
|
1762 @item -faggressive-function-elimination
|
|
|
1763 @opindex @code{faggressive-function-elimination}
|
|
|
1764 @cindex Elimination of functions with identical argument lists
|
|
|
1765 Functions with identical argument lists are eliminated within
|
|
|
1766 statements, regardless of whether these functions are marked
|
|
|
1767 @code{PURE} or not. For example, in
|
|
|
1768 @smallexample
|
|
|
1769 a = f(b,c) + f(b,c)
|
|
|
1770 @end smallexample
|
|
|
1771 there will only be a single call to @code{f}. This option only works
|
|
|
1772 if @option{-ffrontend-optimize} is in effect.
|
|
|
1773
|
|
|
1774 @item -ffrontend-optimize
|
|
|
1775 @opindex @code{frontend-optimize}
|
|
|
1776 @cindex Front-end optimization
|
|
|
1777 This option performs front-end optimization, based on manipulating
|
|
|
1778 parts the Fortran parse tree. Enabled by default by any @option{-O}
|
|
|
1779 option. Optimizations enabled by this option include inlining calls
|
|
|
1780 to @code{MATMUL}, elimination of identical function calls within
|
|
|
1781 expressions, removing unnecessary calls to @code{TRIM} in comparisons
|
|
|
1782 and assignments and replacing @code{TRIM(a)} with
|
|
|
1783 @code{a(1:LEN_TRIM(a))}. It can be deselected by specifying
|
|
|
1784 @option{-fno-frontend-optimize}.
|
|
|
1785 @end table
|
|
|
1786
|
|
|
1787 @xref{Code Gen Options,,Options for Code Generation Conventions,
|
|
|
1788 gcc,Using the GNU Compiler Collection (GCC)}, for information on more options
|
|
|
1789 offered by the GBE
|
|
|
1790 shared by @command{gfortran}, @command{gcc}, and other GNU compilers.
|
|
|
1791
|
|
|
1792 @c man end
|
|
|
1793
|
|
|
1794 @node Interoperability Options
|
|
|
1795 @section Options for interoperability with other languages
|
|
|
1796
|
|
|
1797 @table @asis
|
|
|
1798
|
|
|
1799 @item -fc-prototypes
|
|
|
1800 @opindex @code{c-prototypes}
|
|
|
1801 @cindex Generating C prototypes from Fortran source code
|
|
|
1802 This option will generate C prototypes from @code{BIND(C)} variable
|
|
|
1803 declarations, types and procedure interfaces and writes them to
|
|
|
1804 standard output. @code{ENUM} is not yet supported.
|
|
|
1805
|
|
|
1806 The generated prototypes may need inclusion of an appropriate header,
|
|
|
1807 such as @code{<stdint.h>} or @code{<stdlib.h>}. For types which are
|
|
|
1808 not specified using the appropriate kind from the @code{iso_c_binding}
|
|
|
1809 module, a warning is added as a comment to the code.
|
|
|
1810
|
|
|
1811 For function pointers, a pointer to a function returning @code{int}
|
|
|
1812 without an explicit argument list is generated.
|
|
|
1813
|
|
|
1814 Example of use:
|
|
|
1815 @smallexample
|
|
|
1816 $ gfortran -fc-prototypes -fsyntax-only foo.f90 > foo.h
|
|
|
1817 @end smallexample
|
|
|
1818 where the C code intended for interoperating with the Fortran code
|
|
|
1819 then uses @code{#include "foo.h"}.
|
|
|
1820 @end table
|
|
|
1821
|
|
|
1822 @node Environment Variables
|
|
|
1823 @section Environment variables affecting @command{gfortran}
|
|
|
1824 @cindex environment variable
|
|
|
1825
|
|
|
1826 @c man begin ENVIRONMENT
|
|
|
1827
|
|
|
1828 The @command{gfortran} compiler currently does not make use of any environment
|
|
|
1829 variables to control its operation above and beyond those
|
|
|
1830 that affect the operation of @command{gcc}.
|
|
|
1831
|
|
|
1832 @xref{Environment Variables,,Environment Variables Affecting GCC,
|
|
|
1833 gcc,Using the GNU Compiler Collection (GCC)}, for information on environment
|
|
|
1834 variables.
|
|
|
1835
|
|
|
1836 @xref{Runtime}, for environment variables that affect the
|
|
|
1837 run-time behavior of programs compiled with GNU Fortran.
|
|
|
1838 @c man end
|
