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.

diff --git a/utils/macros.h b/utils/macros.h
index b960475..35ececf 100644 (file)
--- 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