string, wchar: Fix error in C++ mode on glibc systems with clang

[Bruno Haible]

Building a complete gnulib testdir on a glibc system with clang 13, I see
this error (from test-wchar-c++3.cc):

/usr/include/stdlib.h:565:13: error: exception specification in declaration 
does not match previous declaration

This patch fixes it.


2022-04-13  Bruno Haible  <bruno@clisp.org>

        string, wchar: Fix error in C++ mode on glibc systems with clang.
        * lib/string.in.h (free): Add exception specification like glibc does.
        * lib/wchar.in.h (free): Likewise.

diff --git a/lib/string.in.h b/lib/string.in.h
index b818ae9cdf..b6840fa912 100644
--- a/lib/string.in.h
+++ b/lib/string.in.h
@@ -125,14 +125,22 @@ _GL_EXTERN_C void rpl_free (void *);
 #  if defined _MSC_VER
 _GL_EXTERN_C void __cdecl free (void *);
 #  else
+#   if defined __cplusplus && (__GLIBC__ + (__GLIBC_MINOR__ >= 14) > 2)
+_GL_EXTERN_C void free (void *) throw ();
+#   else
 _GL_EXTERN_C void free (void *);
+#   endif
 #  endif
 # endif
 #else
 # if defined _MSC_VER
 _GL_EXTERN_C void __cdecl free (void *);
 # else
+#  if defined __cplusplus && (__GLIBC__ + (__GLIBC_MINOR__ >= 14) > 2)
+_GL_EXTERN_C void free (void *) throw ();
+#  else
 _GL_EXTERN_C void free (void *);
+#  endif
 # endif
 #endif
 
diff --git a/lib/wchar.in.h b/lib/wchar.in.h
index d7792e5fb7..0d5c0b7abe 100644
--- a/lib/wchar.in.h
+++ b/lib/wchar.in.h
@@ -188,14 +188,22 @@ _GL_EXTERN_C void rpl_free (void *);
 #  if defined _MSC_VER
 _GL_EXTERN_C void __cdecl free (void *);
 #  else
+#   if defined __cplusplus && (__GLIBC__ + (__GLIBC_MINOR__ >= 14) > 2)
+_GL_EXTERN_C void free (void *) throw ();
+#   else
 _GL_EXTERN_C void free (void *);
+#   endif
 #  endif
 # endif
 #else
 # if defined _MSC_VER
 _GL_EXTERN_C void __cdecl free (void *);
 # else
+#  if defined __cplusplus && (__GLIBC__ + (__GLIBC_MINOR__ >= 14) > 2)
+_GL_EXTERN_C void free (void *) throw ();
+#  else
 _GL_EXTERN_C void free (void *);
+#  endif
 # endif
 #endif