lang/gcc15: fix build after base d08296c7ab0d

After base d08296c7ab0d7bb259bf7b8cdf9ffb819c1929ab ("libc: Implement
qualifier-preserving standard library functions"), lang/gcc15 fails to
build with errors like:

  /wrkdirs/usr/ports/lang/gcc15/work/gcc-15.2.0/libgomp/affinity-fmt.c: In function 'gomp_display_affinity':
  /wrkdirs/usr/ports/lang/gcc15/work/gcc-15.2.0/libgomp/affinity-fmt.c:330:25: error: initialization discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
    330 |               char *q = strchr (p + 1, '}');
        |                         ^~~~~~

and:

  In file included from /wrkdirs/usr/ports/lang/gcc15/work/.build/gcc/include-fixed/stdio.h:52,
                   from cp-demangle.c:109:
  /wrkdirs/usr/ports/lang/gcc15/work/gcc-15.2.0/libstdc++-v3/../include/libiberty.h:225:14: error: expected identifier or '(' before '_Generic'
    225 | extern void *memrchr(const void *, int, size_t);
        |              ^~~~~~~

The former is because strchr with a 'const char *' input now returns a
'const char*'. This is easily fixed by making 'q' a 'const char *' too.

The latter is because memrchr is now a macro, similar to the other
functions in <string.h>, and libiberty.h attempts to incorrectly
redeclare it.

This is because cp-demangle.c includes libiberty.h, but does not include
the config.h generated for libiberty.h, instead using the config.h
generated for libstdc++.

The problem is really with the way upstream creates its config.h
headers: they should either make libiberty.h automatically include its
own config.h file, or rename that one to libiberty-config.h, so it can
be included at the same time as the libstdc++ config.h header.

The easiest way to fix it is to add a '!defined(__FreeBSD__)'
conditional to the #if statement that attempts to declare the
incompatible memrchr.

Approved by:	salvadore (maintainer)
PR:		297601
MFH:		2026Q3

(cherry picked from commit 955eda5e75ec2f2c177de7005b3b952d9593b7f4)

2 files changed, 22 insertions, 0 deletions

diff --git a/lang/gcc15/files/patch-include_libiberty.h b/lang/gcc15/files/patch-include_libiberty.h
new file mode 100644
index 000000000000..c082051d9f88
--- /dev/null
+++ b/lang/gcc15/files/patch-include_libiberty.h
@@ -0,0 +1,11 @@
+--- include/libiberty.h.orig	2025-08-08 06:51:44 UTC
++++ include/libiberty.h
+@@ -221,7 +221,7 @@ extern int mkstemps(char *, int);
+ 
+ /* Make memrchr available on systems that do not have it.  */
+ #if !defined (__GNU_LIBRARY__ ) && !defined (__linux__) && \
+-    !defined (HAVE_MEMRCHR)
++    !defined (__FreeBSD__) && !defined (HAVE_MEMRCHR)
+ extern void *memrchr(const void *, int, size_t);
+ #endif
+ 
diff --git a/lang/gcc15/files/patch-libgomp_affinity-fmt.c b/lang/gcc15/files/patch-libgomp_affinity-fmt.c
new file mode 100644
index 000000000000..fa3ab1ae484f
--- /dev/null
+++ b/lang/gcc15/files/patch-libgomp_affinity-fmt.c
@@ -0,0 +1,11 @@
+--- libgomp/affinity-fmt.c.orig	2025-08-08 06:51:45 UTC
++++ libgomp/affinity-fmt.c
+@@ -327,7 +327,7 @@ gomp_display_affinity (char *buffer, size_t size,
+ 	      }
+ 	  if (c == '{')
+ 	    {
+-	      char *q = strchr (p + 1, '}');
++	      const char *q = strchr (p + 1, '}');
+ 	      if (q)
+ 		gomp_fatal ("unsupported long type name '%.*s' in affinity "
+ 			    "format", (int) (q - (p + 1)), p + 1);