GCCコンパイラの -pedantic オプションについてメモ。
pedantic
https://eow.alc.co.jp/search?q=pedantic
形容詞
〈侮蔑的〉〔文法・学問的なことなどについて〕重要でない事にこだわり過ぎる、学者ぶった、知識をひけらかす、衒学的な
GCC 2.95.3マニュアル*1より引用。下線部は後続バージョン(3.0)で削除された内容。
-pedantic
Issue all the warnings demanded by strict ANSI C and ISO C++; reject all programs that use forbidden extensions.Valid ANSI C and ISO C++ programs should compile properly with or without this option (though a rare few will require `
-ansi'). However, without this option, certain GNU extensions and traditional C and C++ features are supported as well. With this option, they are rejected.`
-pedantic' does not cause warning messages for use of the alternate keywords whose names begin and end with `__'. Pedantic warnings are also disabled in the expression that follows__extension__. However, only system header files should use these escape routes; application programs should avoid them. See section 4.35 Alternate Keywords.This option is not intended to be useful; it exists only to satisfy pedants who would otherwise claim that GCC fails to support the ANSI standard.
Some users try to use `
-pedantic' to check programs for strict ANSI C conformance. They soon find that it does not do quite what they want: it finds some non-ANSI practices, but not all--only those for which ANSI C requires a diagnostic.A feature to report any failure to conform to ANSI C might be useful in some instances, but would require considerable additional work and would be quite different from `
https://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_2.html#SEC8-pedantic'. We don't have plans to support such a feature in the near future.
GCC 3.0マニュアル*2より引用（下線部は追加内容）。2024年1月現在の最新版GCC 13.2.0マニュアルでもほぼ同一内容。
-pedantic
Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions, and some other programs that do not follow ISO C and ISO C++. For ISO C, follows the version of the ISO C standard specified by any `-std' option used.Valid ISO C and ISO C++ programs should compile properly with or without this option (though a rare few will require `
-ansi' or a `-std' option specifying the required version of ISO C). However, without this option, certain GNU extensions and traditional C and C++ features are supported as well. With this option, they are rejected.`
-pedantic' does not cause warning messages for use of the alternate keywords whose names begin and end with `__'. Pedantic warnings are also disabled in the expression that follows__extension__. However, only system header files should use these escape routes; application programs should avoid them. See section 5.39 Alternate Keywords.Some users try to use `
-pedantic' to check programs for strict ISO C conformance. They soon find that it does not do quite what they want: it finds some non-ISO practices, but not all--only those for which ISO C requires a diagnostic, and some others for which diagnostics have been added.A feature to report any failure to conform to ISO C might be useful in some instances, but would require considerable additional work and would be quite different from `
-pedantic'. We don't have plans to support such a feature in the near future.Where the standard specified with `
https://gcc.gnu.org/onlinedocs/gcc-3.0/gcc_3.html#SEC11-std' represents a GNU extended dialect of C, such as `gnu89' or `gnu99', there is a corresponding base standard, the version of ISO C on which the GNU extended dialect is based. Warnings from `-pedantic' are given where they are required by the base standard. (It would not make sense for such warnings to be given only for features not in the specified GNU C dialect, since by definition the GNU dialects of C include all features the compiler supports with the given option, and there would be nothing to warn about.)
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