[PATCH] Include safe-ctype.h after C++ standard headers, to avoid over-poisoning

[Dimitry Andric <dimitry@andric.com>]

Ref: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111632

When building gcc's C++ sources against recent libc++, the poisoning of
the ctype macros due to including safe-ctype.h before including C++
standard headers such as <list>, <map>, etc, causes many compilation
errors, similar to:

 In file included from /home/dim/src/gcc/master/gcc/gensupport.cc:23:
 In file included from /home/dim/src/gcc/master/gcc/system.h:233:
 In file included from /usr/include/c++/v1/vector:321:
 In file included from
 /usr/include/c++/v1/__format/formatter_bool.h:20:
 In file included from
 /usr/include/c++/v1/__format/formatter_integral.h:32:
 In file included from /usr/include/c++/v1/locale:202:
 /usr/include/c++/v1/__locale:546:5: error: '__abi_tag__' attribute
 only applies to structs, variables, functions, and namespaces
   546 |     _LIBCPP_INLINE_VISIBILITY
       |     ^
 /usr/include/c++/v1/__config:813:37: note: expanded from macro
 '_LIBCPP_INLINE_VISIBILITY'
   813 | #  define _LIBCPP_INLINE_VISIBILITY _LIBCPP_HIDE_FROM_ABI
       |                                     ^
 /usr/include/c++/v1/__config:792:26: note: expanded from macro
 '_LIBCPP_HIDE_FROM_ABI'
   792 |
   __attribute__((__abi_tag__(_LIBCPP_TOSTRING(
 _LIBCPP_VERSIONED_IDENTIFIER))))
       |                          ^
 In file included from /home/dim/src/gcc/master/gcc/gensupport.cc:23:
 In file included from /home/dim/src/gcc/master/gcc/system.h:233:
 In file included from /usr/include/c++/v1/vector:321:
 In file included from
 /usr/include/c++/v1/__format/formatter_bool.h:20:
 In file included from
 /usr/include/c++/v1/__format/formatter_integral.h:32:
 In file included from /usr/include/c++/v1/locale:202:
 /usr/include/c++/v1/__locale:547:37: error: expected ';' at end of
 declaration list
   547 |     char_type toupper(char_type __c) const
       |                                     ^
 /usr/include/c++/v1/__locale:553:48: error: too many arguments
 provided to function-like macro invocation
   553 |     const char_type* toupper(char_type* __low, const
   char_type* __high) const
       |                                                ^
 /home/dim/src/gcc/master/gcc/../include/safe-ctype.h:146:9: note:
 macro 'toupper' defined here
   146 | #define toupper(c) do_not_use_toupper_with_safe_ctype
       |         ^

This is because libc++ uses different transitive includes than
libstdc++, and some of those transitive includes pull in various ctype
declarations (typically via <locale>).

There was already a special case for including <string> before
safe-ctype.h, so move the rest of the C++ standard header includes to
the same location, to fix the problem.

Signed-off-by: Dimitry Andric <dimitry@andric.com>
---
gcc/system.h | 39 ++++++++++++++++++---------------------
1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/gcc/system.h b/gcc/system.h
index e924152ad4c..7a516b11438 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -194,27 +194,8 @@ extern int fprintf_unlocked (FILE *, const char *, ...);
#undef fread_unlocked
#undef fwrite_unlocked

-/* Include <string> before "safe-ctype.h" to avoid GCC poisoning
-   the ctype macros through safe-ctype.h */
-
-#ifdef __cplusplus
-#ifdef INCLUDE_STRING
-# include <string>
-#endif
-#endif
-
-/* There are an extraordinary number of issues with <ctype.h>.
-   The last straw is that it varies with the locale.  Use libiberty's
-   replacement instead.  */
-#include "safe-ctype.h"
-
-#include <sys/types.h>
-
-#include <errno.h>
-
-#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
-extern int errno;
-#endif
+/* Include C++ standard headers before "safe-ctype.h" to avoid GCC
+   poisoning the ctype macros through safe-ctype.h */

#ifdef __cplusplus
#if defined (INCLUDE_ALGORITHM) || !defined (HAVE_SWAP_IN_UTILITY)
@@ -229,6 +210,9 @@ extern int errno;
#ifdef INCLUDE_SET
# include <set>
#endif
+#ifdef INCLUDE_STRING
+# include <string>
+#endif
#ifdef INCLUDE_VECTOR
# include <vector>
#endif
@@ -245,6 +229,19 @@ extern int errno;
# include <type_traits>
#endif

+/* There are an extraordinary number of issues with <ctype.h>.
+   The last straw is that it varies with the locale.  Use libiberty's
+   replacement instead.  */
+#include "safe-ctype.h"
+
+#include <sys/types.h>
+
+#include <errno.h>
+
+#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
+extern int errno;
+#endif
+
/* Some of glibc's string inlines cause warnings.  Plus we'd rather
   rely on (and therefore test) GCC's string builtins.  */
#define __NO_STRING_INLINES
-- 
2.42.0