From d94956b547ca1a477e8b464c58516aca3cccccb9 Mon Sep 17 00:00:00 2001 From: Mark Wooding Date: Wed, 5 Jul 2017 21:23:00 +0100 Subject: [PATCH] utils/macros.h: Refactor the GCC-ish compiler support. Fully define `GCC_VERSION_P' early, and then use it without any other guard to define the GCC-specific hacks. This way, it's easy to support other compilers which behave similarly, by defining an appropriate `FOO_VERSION_P' macro, and then adding appropriate extra alternatives to the individual guards. No functional changes. --- utils/macros.h | 134 ++++++++++++++++++++++++++++----------------------------- 1 file changed, 65 insertions(+), 69 deletions(-) diff --git a/utils/macros.h b/utils/macros.h index b960475..35ececf 100644 --- a/utils/macros.h +++ b/utils/macros.h @@ -47,91 +47,87 @@ /* --- Compiler-specific definitions --- */ #if defined(__GNUC__) - # define GCC_VERSION_P(maj, min) \ (__GNUC__ > (maj) || (__GNUC__ == (maj) && __GNUC_MINOR__ >= (min))) +#else +# define GCC_VERSION_P(maj, min) 0 +#endif -# if GCC_VERSION_P(2, 5) -# define NORETURN __attribute__((noreturn)) -# define PRINTF_LIKE(fix, aix) __attribute__((format(printf, fix, aix))) -# define SCANF_LIKE(fix, aix) __attribute__((format(scanf, fix, aix))) -# define IGNORABLE __attribute__((unused)) -# endif - -# if GCC_VERSION_P(4, 5) -# define DEPRECATED(msg) __attribute__((deprecated(msg))) -# elif GCC_VERSION_P(3, 1) -# define DEPRECATED(msg) __attribute__((deprecated)) -# endif - -# if GCC_VERSION_P(4, 0) -# define EXECL_LIKE(ntrail) __attribute__((sentinel(ntrail))) -# endif - -# if GCC_VERSION_P(4, 6) - - /* --- Diagnostic suppression in GCC: a tale of woe --- * - * - * This is extremely unpleasant, largely as a result of bugs in the GCC - * preprocessor's handling of @_Pragma@. The fundamental problem is - * that it's the preprocessor, and not the compiler proper, which - * detects @_Pragma@, emitting @#pragma@ lines into its output; and it - * does it during macro expansion, even if the macro is being expanded - * during argument collection. Since arguments are expanded before - * replacing the macro's invocation with its body, a pragma in an - * argument will be emitted %%\emph{before}%% any pragmata in the body, - * even if they appear before the argument in the body -- and even if - * the argument doesn't actually appear anywhere at all in the body. - * - * Another, rather less significant, problem is that @_Pragma@'s - * argument is a single string literal, recognized in translation phase - * 4, before string-literal concatenation in phase 6, so we must build - * pragma bodies as token lists and then stringify them. - * - * As a result, we need some subterfuge here. The @MLIB__PRAGMA_HACK@ - * macro issues a @_Pragma@ on its argument token list, which it - * stringifies; this deals with the second problem. The first is - * trickier: we must delay expansion of @MLIB__PRAGMA_HACK@ from the - * argument collection phase to the body rescanning phase, and we do - * this by splitting the invocations between @GCC_WARNING@ macro calls: - * the name is left hanging from the previous call (or from - * @MLIB__MUFFLE_WARNINGS@, in the first case) and the body is supplied - * by @GCC_WARNING@, which also supplies the next @MLIB__PRAGMA_HACK@. - * The remaining problem is to make sure we can dispose of the final - * trailing @MLIB__PRAGMA_HACK@ harmlessly, which we do by introducing - * an extra argument @emitp@, which may be either @t@ or @nil@; this - * dispatches to an appropriate helper macro by means of token-pasting. - * - * I'm so sorry. - */ - -# define MLIB__PRAGMA_HACK_t(x) _Pragma(#x) -# define MLIB__PRAGMA_HACK_nil(x) -# define MLIB__PRAGMA_HACK(emitp, x) MLIB__PRAGMA_HACK_##emitp(x) -# define MLIB__MUFFLE_WARNINGS(warns, body) \ +#if GCC_VERSION_P(2, 5) +# define NORETURN __attribute__((noreturn)) +# define PRINTF_LIKE(fix, aix) __attribute__((format(printf, fix, aix))) +# define SCANF_LIKE(fix, aix) __attribute__((format(scanf, fix, aix))) +# define IGNORABLE __attribute__((unused)) +#endif + +#if GCC_VERSION_P(4, 5) +# define DEPRECATED(msg) __attribute__((deprecated(msg))) +#elif GCC_VERSION_P(3, 1) +# define DEPRECATED(msg) __attribute__((deprecated)) +#endif + +#if GCC_VERSION_P(4, 0) +# define EXECL_LIKE(ntrail) __attribute__((sentinel(ntrail))) +#endif + +#if GCC_VERSION_P(4, 6) + + /* --- Diagnostic suppression in GCC: a tale of woe --- * + * + * This is extremely unpleasant, largely as a result of bugs in the GCC + * preprocessor's handling of @_Pragma@. The fundamental problem is + * that it's the preprocessor, and not the compiler proper, which + * detects @_Pragma@, emitting @#pragma@ lines into its output; and it + * does it during macro expansion, even if the macro is being expanded + * during argument collection. Since arguments are expanded before + * replacing the macro's invocation with its body, a pragma in an + * argument will be emitted %%\emph{before}%% any pragmata in the body, + * even if they appear before the argument in the body -- and even if + * the argument doesn't actually appear anywhere at all in the body. + * + * Another, rather less significant, problem is that @_Pragma@'s + * argument is a single string literal, recognized in translation phase + * 4, before string-literal concatenation in phase 6, so we must build + * pragma bodies as token lists and then stringify them. + * + * As a result, we need some subterfuge here. The @MLIB__PRAGMA_HACK@ + * macro issues a @_Pragma@ on its argument token list, which it + * stringifies; this deals with the second problem. The first is + * trickier: we must delay expansion of @MLIB__PRAGMA_HACK@ from the + * argument collection phase to the body rescanning phase, and we do + * this by splitting the invocations between @GCC_WARNING@ macro calls: + * the name is left hanging from the previous call (or from + * @MLIB__MUFFLE_WARNINGS@, in the first case) and the body is supplied + * by @GCC_WARNING@, which also supplies the next @MLIB__PRAGMA_HACK@. + * The remaining problem is to make sure we can dispose of the final + * trailing @MLIB__PRAGMA_HACK@ harmlessly, which we do by introducing + * an extra argument @emitp@, which may be either @t@ or @nil@; this + * dispatches to an appropriate helper macro by means of token-pasting. + * + * I'm so sorry. + */ + +# define MLIB__PRAGMA_HACK_t(x) _Pragma(#x) +# define MLIB__PRAGMA_HACK_nil(x) +# define MLIB__PRAGMA_HACK(emitp, x) MLIB__PRAGMA_HACK_##emitp(x) +# define MLIB__MUFFLE_WARNINGS(warns, body) \ _Pragma("GCC diagnostic push") MLIB__PRAGMA_HACK \ warns \ (nil, nil) \ body \ _Pragma("GCC diagnostic pop") -# define GCC_WARNING(warn) \ +# define GCC_WARNING(warn) \ (t, GCC diagnostic ignored warn) MLIB__PRAGMA_HACK -# define MUFFLE_WARNINGS_DECL(warns, body) \ +# define MUFFLE_WARNINGS_DECL(warns, body) \ MLIB__MUFFLE_WARNINGS(warns, body) -# define MUFFLE_WARNINGS_EXPR(warns, body) \ +# define MUFFLE_WARNINGS_EXPR(warns, body) \ __extension__ ({ MLIB__MUFFLE_WARNINGS(warns, (body);) }) -# define MUFFLE_WARNINGS_STMT(warns, body) \ +# define MUFFLE_WARNINGS_STMT(warns, body) \ do { MLIB__MUFFLE_WARNINGS(warns, body) } while (0) -# endif - #endif /* --- Fallback definitions, mostly trivial --- */ -#ifndef GCC_VERSION_P -# define GCC_VERSION_P(maj, min) 0 -#endif - #ifndef DEPRECATED # define DEPRECATED(msg) #endif -- 2.11.0