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1 @c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
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2 @c 2000, 2001, 2002, 2003, 2004, 2005, 2008 Free Software Foundation, Inc.
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3 @c This is part of the GCC manual.
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4 @c For copying conditions, see the file gccint.texi.
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5
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6 @node Host Config
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7 @chapter Host Configuration
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8 @cindex host configuration
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9
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10 Most details about the machine and system on which the compiler is
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11 actually running are detected by the @command{configure} script. Some
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12 things are impossible for @command{configure} to detect; these are
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13 described in two ways, either by macros defined in a file named
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14 @file{xm-@var{machine}.h} or by hook functions in the file specified
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15 by the @var{out_host_hook_obj} variable in @file{config.gcc}. (The
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16 intention is that very few hosts will need a header file but nearly
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17 every fully supported host will need to override some hooks.)
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18
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19 If you need to define only a few macros, and they have simple
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20 definitions, consider using the @code{xm_defines} variable in your
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21 @file{config.gcc} entry instead of creating a host configuration
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22 header. @xref{System Config}.
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23
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24 @menu
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25 * Host Common:: Things every host probably needs implemented.
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26 * Filesystem:: Your host can't have the letter `a' in filenames?
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27 * Host Misc:: Rare configuration options for hosts.
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28 @end menu
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29
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30 @node Host Common
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31 @section Host Common
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32 @cindex host hooks
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33 @cindex host functions
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34
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35 Some things are just not portable, even between similar operating systems,
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36 and are too difficult for autoconf to detect. They get implemented using
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37 hook functions in the file specified by the @var{host_hook_obj}
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38 variable in @file{config.gcc}.
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39
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40 @deftypefn {Host Hook} void HOST_HOOKS_EXTRA_SIGNALS (void)
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41 This host hook is used to set up handling for extra signals. The most
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42 common thing to do in this hook is to detect stack overflow.
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43 @end deftypefn
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44
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45 @deftypefn {Host Hook} void * HOST_HOOKS_GT_PCH_GET_ADDRESS (size_t @var{size}, int @var{fd})
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46 This host hook returns the address of some space that is likely to be
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47 free in some subsequent invocation of the compiler. We intend to load
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48 the PCH data at this address such that the data need not be relocated.
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49 The area should be able to hold @var{size} bytes. If the host uses
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50 @code{mmap}, @var{fd} is an open file descriptor that can be used for
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51 probing.
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52 @end deftypefn
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53
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54 @deftypefn {Host Hook} int HOST_HOOKS_GT_PCH_USE_ADDRESS (void * @var{address}, size_t @var{size}, int @var{fd}, size_t @var{offset})
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55 This host hook is called when a PCH file is about to be loaded.
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56 We want to load @var{size} bytes from @var{fd} at @var{offset}
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57 into memory at @var{address}. The given address will be the result of
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58 a previous invocation of @code{HOST_HOOKS_GT_PCH_GET_ADDRESS}.
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59 Return @minus{}1 if we couldn't allocate @var{size} bytes at @var{address}.
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60 Return 0 if the memory is allocated but the data is not loaded. Return 1
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61 if the hook has performed everything.
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62
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63 If the implementation uses reserved address space, free any reserved
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64 space beyond @var{size}, regardless of the return value. If no PCH will
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65 be loaded, this hook may be called with @var{size} zero, in which case
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66 all reserved address space should be freed.
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67
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68 Do not try to handle values of @var{address} that could not have been
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69 returned by this executable; just return @minus{}1. Such values usually
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70 indicate an out-of-date PCH file (built by some other GCC executable),
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71 and such a PCH file won't work.
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72 @end deftypefn
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73
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74 @deftypefn {Host Hook} size_t HOST_HOOKS_GT_PCH_ALLOC_GRANULARITY (void);
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75 This host hook returns the alignment required for allocating virtual
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76 memory. Usually this is the same as getpagesize, but on some hosts the
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77 alignment for reserving memory differs from the pagesize for committing
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78 memory.
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79 @end deftypefn
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80
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81 @node Filesystem
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82 @section Host Filesystem
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83 @cindex configuration file
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84 @cindex @file{xm-@var{machine}.h}
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85
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86 GCC needs to know a number of things about the semantics of the host
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87 machine's filesystem. Filesystems with Unix and MS-DOS semantics are
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88 automatically detected. For other systems, you can define the
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89 following macros in @file{xm-@var{machine}.h}.
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90
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91 @ftable @code
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92 @item HAVE_DOS_BASED_FILE_SYSTEM
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93 This macro is automatically defined by @file{system.h} if the host
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94 file system obeys the semantics defined by MS-DOS instead of Unix.
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95 DOS file systems are case insensitive, file specifications may begin
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96 with a drive letter, and both forward slash and backslash (@samp{/}
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97 and @samp{\}) are directory separators.
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98
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99 @item DIR_SEPARATOR
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100 @itemx DIR_SEPARATOR_2
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101 If defined, these macros expand to character constants specifying
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102 separators for directory names within a file specification.
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103 @file{system.h} will automatically give them appropriate values on
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104 Unix and MS-DOS file systems. If your file system is neither of
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105 these, define one or both appropriately in @file{xm-@var{machine}.h}.
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106
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107 However, operating systems like VMS, where constructing a pathname is
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108 more complicated than just stringing together directory names
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109 separated by a special character, should not define either of these
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110 macros.
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111
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112 @item PATH_SEPARATOR
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113 If defined, this macro should expand to a character constant
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114 specifying the separator for elements of search paths. The default
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115 value is a colon (@samp{:}). DOS-based systems usually, but not
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116 always, use semicolon (@samp{;}).
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117
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118 @item VMS
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119 Define this macro if the host system is VMS@.
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120
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121 @item HOST_OBJECT_SUFFIX
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122 Define this macro to be a C string representing the suffix for object
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123 files on your host machine. If you do not define this macro, GCC will
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124 use @samp{.o} as the suffix for object files.
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125
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126 @item HOST_EXECUTABLE_SUFFIX
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127 Define this macro to be a C string representing the suffix for
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128 executable files on your host machine. If you do not define this macro,
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129 GCC will use the null string as the suffix for executable files.
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130
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131 @item HOST_BIT_BUCKET
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132 A pathname defined by the host operating system, which can be opened as
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133 a file and written to, but all the information written is discarded.
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134 This is commonly known as a @dfn{bit bucket} or @dfn{null device}. If
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135 you do not define this macro, GCC will use @samp{/dev/null} as the bit
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136 bucket. If the host does not support a bit bucket, define this macro to
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137 an invalid filename.
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138
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139 @item UPDATE_PATH_HOST_CANONICALIZE (@var{path})
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140 If defined, a C statement (sans semicolon) that performs host-dependent
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141 canonicalization when a path used in a compilation driver or
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142 preprocessor is canonicalized. @var{path} is a malloc-ed path to be
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143 canonicalized. If the C statement does canonicalize @var{path} into a
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144 different buffer, the old path should be freed and the new buffer should
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145 have been allocated with malloc.
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146
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147 @item DUMPFILE_FORMAT
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148 Define this macro to be a C string representing the format to use for
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149 constructing the index part of debugging dump file names. The resultant
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150 string must fit in fifteen bytes. The full filename will be the
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151 concatenation of: the prefix of the assembler file name, the string
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152 resulting from applying this format to an index number, and a string
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153 unique to each dump file kind, e.g.@: @samp{rtl}.
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154
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155 If you do not define this macro, GCC will use @samp{.%02d.}. You should
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156 define this macro if using the default will create an invalid file name.
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157
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158 @item DELETE_IF_ORDINARY
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159 Define this macro to be a C statement (sans semicolon) that performs
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160 host-dependent removal of ordinary temp files in the compilation driver.
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161
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162 If you do not define this macro, GCC will use the default version. You
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163 should define this macro if the default version does not reliably remove
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164 the temp file as, for example, on VMS which allows multiple versions
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165 of a file.
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166
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167 @item HOST_LACKS_INODE_NUMBERS
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168 Define this macro if the host filesystem does not report meaningful inode
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169 numbers in struct stat.
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170 @end ftable
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171
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172 @node Host Misc
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173 @section Host Misc
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174 @cindex configuration file
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175 @cindex @file{xm-@var{machine}.h}
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176
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177 @ftable @code
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178 @item FATAL_EXIT_CODE
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179 A C expression for the status code to be returned when the compiler
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180 exits after serious errors. The default is the system-provided macro
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181 @samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that
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182 macro. Define this macro only if these defaults are incorrect.
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183
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184 @item SUCCESS_EXIT_CODE
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185 A C expression for the status code to be returned when the compiler
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186 exits without serious errors. (Warnings are not serious errors.) The
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187 default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if
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188 the system doesn't define that macro. Define this macro only if these
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189 defaults are incorrect.
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190
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191 @item USE_C_ALLOCA
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192 Define this macro if GCC should use the C implementation of @code{alloca}
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193 provided by @file{libiberty.a}. This only affects how some parts of the
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194 compiler itself allocate memory. It does not change code generation.
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195
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196 When GCC is built with a compiler other than itself, the C @code{alloca}
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197 is always used. This is because most other implementations have serious
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198 bugs. You should define this macro only on a system where no
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199 stack-based @code{alloca} can possibly work. For instance, if a system
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200 has a small limit on the size of the stack, GCC's builtin @code{alloca}
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201 will not work reliably.
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202
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203 @item COLLECT2_HOST_INITIALIZATION
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204 If defined, a C statement (sans semicolon) that performs host-dependent
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205 initialization when @code{collect2} is being initialized.
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206
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207 @item GCC_DRIVER_HOST_INITIALIZATION
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208 If defined, a C statement (sans semicolon) that performs host-dependent
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209 initialization when a compilation driver is being initialized.
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210
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211 @item HOST_LONG_LONG_FORMAT
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212 If defined, the string used to indicate an argument of type @code{long
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213 long} to functions like @code{printf}. The default value is
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214 @code{"ll"}.
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215 @end ftable
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216
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217 In addition, if @command{configure} generates an incorrect definition of
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218 any of the macros in @file{auto-host.h}, you can override that
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219 definition in a host configuration header. If you need to do this,
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220 first see if it is possible to fix @command{configure}.
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