[PATCH] #undef isblank before def or decl in libstdc++ headers

[Olivier Hainque]

(Thanks for your feedback Jonathan)

> On 10 Dec 2021, at 19:24, Jonathan Wakely <jwakely@redhat.com> wrote:
> 
> I'm curious why _GLIBCXX_USE_C99_CTYPE_TR1 is not defined if VxWorks
> has isblank, the configure check is:

Oh, hmm, very good point. The reason was that the definition
of isblank is conditioned on _C99/_HAS_C9X as well, so the need
for which we had introduced the definition in os_defines.h
would better be generalized.

	* config/vxworks.h (VXWORKS_OS_CPP_BUILTINS): Define
	_C99 for C++.

--- a/gcc/config/vxworks.h
+++ b/gcc/config/vxworks.h
@@ -328,6 +328,10 @@ extern void vxworks_asm_out_destructor (rtx symbol, int priority);
 	   if (!flag_isoc99 && !c_dialect_cxx())			\
              builtin_define ("_ALLOW_KEYWORD_MACROS");			\
         }								\
+      /* C++ support relies on C99 features.  Make sure they are	\
+	 exposed by the system headers.  */				\
+      if (c_dialect_cxx())						\
+	builtin_define("_C99");						\
     }									\
   while (0)


Works with the two libstdc++ changes reverted, and gives
"configure" a better view of what's there.

Makes sense?