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annotate gcc/doc/standards.texi @ 63:b7f97abdc517 gcc-4.6-20100522
update gcc from gcc-4.5.0 to gcc-4.6
| author | ryoma <e075725@ie.u-ryukyu.ac.jp> |
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| date | Mon, 24 May 2010 12:47:05 +0900 |
| parents | 77e2b8dfacca |
| children | f6334be47118 |
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1 @c Copyright (C) 2000, 2001, 2002, 2004, 2006, 2007, 2008, 2010 |
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2 @c Free Software Foundation, Inc. |
| 0 | 3 @c This is part of the GCC manual. |
| 4 @c For copying conditions, see the file gcc.texi. | |
| 5 | |
| 6 @node Standards | |
| 7 @chapter Language Standards Supported by GCC | |
| 8 | |
| 9 For each language compiled by GCC for which there is a standard, GCC | |
| 10 attempts to follow one or more versions of that standard, possibly | |
| 11 with some exceptions, and possibly with some extensions. | |
| 12 | |
| 13 @section C language | |
| 14 @cindex C standard | |
| 15 @cindex C standards | |
| 16 @cindex ANSI C standard | |
| 17 @cindex ANSI C | |
| 18 @cindex ANSI C89 | |
| 19 @cindex C89 | |
| 20 @cindex ANSI X3.159-1989 | |
| 21 @cindex X3.159-1989 | |
| 22 @cindex ISO C standard | |
| 23 @cindex ISO C | |
| 24 @cindex ISO C90 | |
| 25 @cindex ISO/IEC 9899 | |
| 26 @cindex ISO 9899 | |
| 27 @cindex C90 | |
| 28 @cindex ISO C94 | |
| 29 @cindex C94 | |
| 30 @cindex ISO C95 | |
| 31 @cindex C95 | |
| 32 @cindex ISO C99 | |
| 33 @cindex C99 | |
| 34 @cindex ISO C9X | |
| 35 @cindex C9X | |
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36 @cindex ISO C1X |
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37 @cindex C1X |
| 0 | 38 @cindex Technical Corrigenda |
| 39 @cindex TC1 | |
| 40 @cindex Technical Corrigendum 1 | |
| 41 @cindex TC2 | |
| 42 @cindex Technical Corrigendum 2 | |
| 43 @cindex TC3 | |
| 44 @cindex Technical Corrigendum 3 | |
| 45 @cindex AMD1 | |
| 46 @cindex freestanding implementation | |
| 47 @cindex freestanding environment | |
| 48 @cindex hosted implementation | |
| 49 @cindex hosted environment | |
| 50 @findex __STDC_HOSTED__ | |
| 51 | |
| 52 GCC supports three versions of the C standard, although support for | |
| 53 the most recent version is not yet complete. | |
| 54 | |
| 55 @opindex std | |
| 56 @opindex ansi | |
| 57 @opindex pedantic | |
| 58 @opindex pedantic-errors | |
| 59 The original ANSI C standard (X3.159-1989) was ratified in 1989 and | |
| 60 published in 1990. This standard was ratified as an ISO standard | |
| 61 (ISO/IEC 9899:1990) later in 1990. There were no technical | |
| 62 differences between these publications, although the sections of the | |
| 63 ANSI standard were renumbered and became clauses in the ISO standard. | |
| 64 This standard, in both its forms, is commonly known as @dfn{C89}, or | |
| 65 occasionally as @dfn{C90}, from the dates of ratification. The ANSI | |
| 66 standard, but not the ISO standard, also came with a Rationale | |
| 67 document. To select this standard in GCC, use one of the options | |
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68 @option{-ansi}, @option{-std=c90} or @option{-std=iso9899:1990}; to obtain |
| 0 | 69 all the diagnostics required by the standard, you should also specify |
| 70 @option{-pedantic} (or @option{-pedantic-errors} if you want them to be | |
| 71 errors rather than warnings). @xref{C Dialect Options,,Options | |
| 72 Controlling C Dialect}. | |
| 73 | |
| 74 Errors in the 1990 ISO C standard were corrected in two Technical | |
| 75 Corrigenda published in 1994 and 1996. GCC does not support the | |
| 76 uncorrected version. | |
| 77 | |
| 78 An amendment to the 1990 standard was published in 1995. This | |
| 79 amendment added digraphs and @code{__STDC_VERSION__} to the language, | |
| 80 but otherwise concerned the library. This amendment is commonly known | |
| 81 as @dfn{AMD1}; the amended standard is sometimes known as @dfn{C94} or | |
| 82 @dfn{C95}. To select this standard in GCC, use the option | |
| 83 @option{-std=iso9899:199409} (with, as for other standard versions, | |
| 84 @option{-pedantic} to receive all required diagnostics). | |
| 85 | |
| 86 A new edition of the ISO C standard was published in 1999 as ISO/IEC | |
| 87 9899:1999, and is commonly known as @dfn{C99}. GCC has incomplete | |
| 88 support for this standard version; see | |
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89 @uref{http://gcc.gnu.org/c99status.html} for details. To select this |
| 0 | 90 standard, use @option{-std=c99} or @option{-std=iso9899:1999}. (While in |
| 91 development, drafts of this standard version were referred to as | |
| 92 @dfn{C9X}.) | |
| 93 | |
| 94 Errors in the 1999 ISO C standard were corrected in three Technical | |
| 95 Corrigenda published in 2001, 2004 and 2007. GCC does not support the | |
| 96 uncorrected version. | |
| 97 | |
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98 A fourth version of the C standard, known as @dfn{C1X}, is under |
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99 development; GCC has limited preliminary support for parts of this |
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100 standard, enabled with @option{-std=c1x}. |
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101 |
| 0 | 102 By default, GCC provides some extensions to the C language that on |
| 103 rare occasions conflict with the C standard. @xref{C | |
| 104 Extensions,,Extensions to the C Language Family}. Use of the | |
| 105 @option{-std} options listed above will disable these extensions where | |
| 106 they conflict with the C standard version selected. You may also | |
| 107 select an extended version of the C language explicitly with | |
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108 @option{-std=gnu90} (for C90 with GNU extensions), @option{-std=gnu99} |
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109 (for C99 with GNU extensions) or @option{-std=gnu1x} (for C1X with GNU |
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110 extensions). The default, if no C language dialect |
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111 options are given, is @option{-std=gnu90}; this will change to |
| 0 | 112 @option{-std=gnu99} in some future release when the C99 support is |
| 113 complete. Some features that are part of the C99 standard are | |
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114 accepted as extensions in C90 mode. |
| 0 | 115 |
| 116 The ISO C standard defines (in clause 4) two classes of conforming | |
| 117 implementation. A @dfn{conforming hosted implementation} supports the | |
| 118 whole standard including all the library facilities; a @dfn{conforming | |
| 119 freestanding implementation} is only required to provide certain | |
| 120 library facilities: those in @code{<float.h>}, @code{<limits.h>}, | |
| 121 @code{<stdarg.h>}, and @code{<stddef.h>}; since AMD1, also those in | |
| 122 @code{<iso646.h>}; and in C99, also those in @code{<stdbool.h>} and | |
| 123 @code{<stdint.h>}. In addition, complex types, added in C99, are not | |
| 124 required for freestanding implementations. The standard also defines | |
| 125 two environments for programs, a @dfn{freestanding environment}, | |
| 126 required of all implementations and which may not have library | |
| 127 facilities beyond those required of freestanding implementations, | |
| 128 where the handling of program startup and termination are | |
| 129 implementation-defined, and a @dfn{hosted environment}, which is not | |
| 130 required, in which all the library facilities are provided and startup | |
| 131 is through a function @code{int main (void)} or @code{int main (int, | |
| 132 char *[])}. An OS kernel would be a freestanding environment; a | |
| 133 program using the facilities of an operating system would normally be | |
| 134 in a hosted implementation. | |
| 135 | |
| 136 @opindex ffreestanding | |
| 137 GCC aims towards being usable as a conforming freestanding | |
| 138 implementation, or as the compiler for a conforming hosted | |
| 139 implementation. By default, it will act as the compiler for a hosted | |
| 140 implementation, defining @code{__STDC_HOSTED__} as @code{1} and | |
| 141 presuming that when the names of ISO C functions are used, they have | |
| 142 the semantics defined in the standard. To make it act as a conforming | |
| 143 freestanding implementation for a freestanding environment, use the | |
| 144 option @option{-ffreestanding}; it will then define | |
| 145 @code{__STDC_HOSTED__} to @code{0} and not make assumptions about the | |
| 146 meanings of function names from the standard library, with exceptions | |
| 147 noted below. To build an OS kernel, you may well still need to make | |
| 148 your own arrangements for linking and startup. | |
| 149 @xref{C Dialect Options,,Options Controlling C Dialect}. | |
| 150 | |
| 151 GCC does not provide the library facilities required only of hosted | |
| 152 implementations, nor yet all the facilities required by C99 of | |
| 153 freestanding implementations; to use the facilities of a hosted | |
| 154 environment, you will need to find them elsewhere (for example, in the | |
| 155 GNU C library). @xref{Standard Libraries,,Standard Libraries}. | |
| 156 | |
| 157 Most of the compiler support routines used by GCC are present in | |
| 158 @file{libgcc}, but there are a few exceptions. GCC requires the | |
| 159 freestanding environment provide @code{memcpy}, @code{memmove}, | |
| 160 @code{memset} and @code{memcmp}. | |
| 161 Finally, if @code{__builtin_trap} is used, and the target does | |
| 162 not implement the @code{trap} pattern, then GCC will emit a call | |
| 163 to @code{abort}. | |
| 164 | |
| 165 For references to Technical Corrigenda, Rationale documents and | |
| 166 information concerning the history of C that is available online, see | |
| 167 @uref{http://gcc.gnu.org/readings.html} | |
| 168 | |
| 169 @section C++ language | |
| 170 | |
| 171 GCC supports the ISO C++ standard (1998) and contains experimental | |
| 172 support for the upcoming ISO C++ standard (200x). | |
| 173 | |
| 174 The original ISO C++ standard was published as the ISO standard (ISO/IEC | |
| 175 14882:1998) and amended by a Technical Corrigenda published in 2003 | |
| 176 (ISO/IEC 14882:2003). These standards are referred to as C++98 and | |
| 177 C++03, respectively. GCC implements the majority of C++98 (@code{export} | |
| 178 is a notable exception) and most of the changes in C++03. To select | |
| 179 this standard in GCC, use one of the options @option{-ansi} or | |
| 180 @option{-std=c++98}; to obtain all the diagnostics required by the | |
| 181 standard, you should also specify @option{-pedantic} (or | |
| 182 @option{-pedantic-errors} if you want them to be errors rather than | |
| 183 warnings). | |
| 184 | |
| 185 The ISO C++ committee is working on a new ISO C++ standard, dubbed | |
| 186 C++0x, that is intended to be published by 2009. C++0x contains several | |
| 187 changes to the C++ language, some of which have been implemented in an | |
| 188 experimental C++0x mode in GCC@. The C++0x mode in GCC tracks the draft | |
| 189 working paper for the C++0x standard; the latest working paper is | |
| 190 available on the ISO C++ committee's web site at | |
| 191 @uref{http://www.open-std.org/jtc1/sc22/wg21/}. For information | |
| 192 regarding the C++0x features available in the experimental C++0x mode, | |
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193 see @uref{http://gcc.gnu.org/projects/cxx0x.html}. To select this |
| 0 | 194 standard in GCC, use the option @option{-std=c++0x}; to obtain all the |
| 195 diagnostics required by the standard, you should also specify | |
| 196 @option{-pedantic} (or @option{-pedantic-errors} if you want them to be | |
| 197 errors rather than warnings). | |
| 198 | |
| 199 By default, GCC provides some extensions to the C++ language; @xref{C++ | |
| 200 Dialect Options,Options Controlling C++ Dialect}. Use of the | |
| 201 @option{-std} option listed above will disable these extensions. You | |
| 202 may also select an extended version of the C++ language explicitly with | |
| 203 @option{-std=gnu++98} (for C++98 with GNU extensions) or | |
| 204 @option{-std=gnu++0x} (for C++0x with GNU extensions). The default, if | |
| 205 no C++ language dialect options are given, is @option{-std=gnu++98}. | |
| 206 | |
| 207 @section Objective-C and Objective-C++ languages | |
| 208 @cindex Objective-C | |
| 209 @cindex Objective-C++ | |
| 210 | |
| 211 There is no formal written standard for Objective-C or Objective-C++@. The most | |
| 212 authoritative manual is ``Object-Oriented Programming and the | |
| 213 Objective-C Language'', available at a number of web sites: | |
| 214 | |
| 215 @itemize | |
| 216 @item | |
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217 @uref{http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/} |
| 0 | 218 is a recent (and periodically updated) version; |
| 219 @item | |
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220 @uref{http://objc.toodarkpark.net} |
| 0 | 221 is an older example; |
| 222 @item | |
| 223 @uref{http://www.gnustep.org} | |
| 224 and | |
| 225 @uref{http://gcc.gnu.org/readings.html} | |
| 226 have additional useful information. | |
| 227 @end itemize | |
| 228 | |
| 229 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, | |
| 230 GNAT Reference Manual}, for information on standard | |
| 231 conformance and compatibility of the Ada compiler. | |
| 232 | |
| 233 @xref{Standards,,Standards, gfortran, The GNU Fortran Compiler}, for details | |
| 234 of standards supported by GNU Fortran. | |
| 235 | |
| 236 @xref{Compatibility,,Compatibility with the Java Platform, gcj, GNU gcj}, | |
| 237 for details of compatibility between @command{gcj} and the Java Platform. |