Last attempt at <tgmath.h>: do enable the new code for C11 compilers.

I was thinking by myself, if the new code doesn't work with GCC 4.2, why
not simply turn it into an efficient version for C11 compilers? By
changing the code to use _Generic() directly in that case, I can build
the tgmath regression test in a matter of milliseconds with Clang,
instead of the 8 seconds it used to take.

So by the time C11 becomes the default, it will pick up the new code
automatically. And now I will refrain from making more changes to
<tgmath.h>.

1 files changed, 17 insertions, 11 deletions

diff --git a/include/tgmath.h b/include/tgmath.h
index 9de0afe4248b..9302302658fb 100644
--- a/include/tgmath.h
+++ b/include/tgmath.h
@@ -53,19 +53,23 @@
  * Note that these macros cannot be implemented with C's ?: operator,
  * because the return type of the whole expression would incorrectly be long
  * double complex regardless of the argument types.
+ *
+ * The structure of the C11 implementation of these macros can in
+ * principle be reused for non-C11 compilers, but due to an integer
+ * promotion bug for complex types in GCC 4.2, simply let non-C11
+ * compilers use an inefficient yet reliable version.
  */
 
-#ifndef __generic
-#error "<tgmath.h> not implemented for this compiler"
-#endif
-
-#if 0 /* XXX: Much shorter and faster to compile, but broken with GCC 4.2. */
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
 #define	__tg_generic(x, cfnl, cfn, cfnf, fnl, fn, fnf)			\
-	__generic(x, long double _Complex, cfnl,			\
-	    __generic(x, double _Complex, cfn,				\
-	        __generic(x, float _Complex, cfnf,			\
-	            __generic(x, long double, fnl,			\
-	                __generic(x, float, fnf, fn)))))
+	_Generic(x,							\
+		long double _Complex: cfnl,				\
+		double _Complex: cfn,					\
+		float _Complex: cfnf,					\
+		long double: fnl,					\
+		default: fn,						\
+		float: fnf						\
+	)
 #define	__tg_type(x)							\
 	__tg_generic(x, (long double _Complex)0, (double _Complex)0,	\
 	    (float _Complex)0, (long double)0, (double)0, (float)0)
@@ -77,7 +81,7 @@
 	__tg_generic(							\
 	    __tg_type(x) + __tg_type(y),				\
 	    cfnl, cfn, cfnf, fnl, fn, fnf)(__VA_ARGS__)
-#else
+#elif defined(__generic)
 #define	__tg_generic_simple(x, fnl, fn, fnf)				\
 	__generic(x, long double _Complex, fnl,				\
 	    __generic(x, double _Complex, fn,				\
@@ -113,6 +117,8 @@
 	    __tg_generic_full(y, cfnl, cfn , cfn , fnl , fn  , fn  ),	\
 	    __tg_generic_full(y, cfnl, cfn , cfnf, fnl , fn  , fnf ))	\
 	    (__VA_ARGS__)
+#else
+#error "<tgmath.h> not implemented for this compiler"
 #endif
 
 /* Macros to save lots of repetition below */