Enable support for GCC 11 -Wmismatched-dealloc.

To help detect common kinds of memory (and other resource) management
bugs, GCC 11 adds support for the detection of mismatched calls to
allocation and deallocation functions.  At each call site to a known
deallocation function GCC checks the set of allocation functions
the former can be paired with and, if the two don't match, issues
a -Wmismatched-dealloc warning (something similar happens in C++
for mismatched calls to new and delete).  GCC also uses the same
mechanism to detect attempts to deallocate objects not allocated
by any allocation function (or pointers past the first byte into
allocated objects) by -Wfree-nonheap-object.

This support is enabled for built-in functions like malloc and free.
To extend it beyond those, GCC extends attribute malloc to designate
a deallocation function to which pointers returned from the allocation
function may be passed to deallocate the allocated objects.  Another,
optional argument designates the positional argument to which
the pointer must be passed.

This change is the first step in enabling this extended support for
Glibc.

1 files changed, 17 insertions, 2 deletions

diff --git a/wcsmbs/wchar.h b/wcsmbs/wchar.h
index ce0acb1c28..075776890f 100644
--- a/wcsmbs/wchar.h
+++ b/wcsmbs/wchar.h
@@ -151,7 +151,8 @@ extern size_t wcsxfrm_l (wchar_t *__s1, const wchar_t *__s2,
 			 size_t __n, locale_t __loc) __THROW;
 
 /* Duplicate S, returning an identical malloc'd string.  */
-extern wchar_t *wcsdup (const wchar_t *__s) __THROW __attribute_malloc__;
+extern wchar_t *wcsdup (const wchar_t *__s) __THROW
+  __attribute_malloc__ __attr_dealloc_free;
 #endif
 
 /* Find the first occurrence of WC in WCS.  */
@@ -562,9 +563,23 @@ extern wchar_t *wcpncpy (wchar_t *__restrict __dest,
 /* Wide character I/O functions.  */
 
 #if defined __USE_XOPEN2K8 || __GLIBC_USE (LIB_EXT2)
+# ifndef __attr_dealloc_fclose
+#   if defined __has_builtin
+#     if __has_builtin (__builtin_fclose)
+/* If the attribute macro hasn't been defined yet (by <stdio.h>) and
+   fclose is a built-in, use it.  */
+#      define __attr_dealloc_fclose __attr_dealloc (__builtin_fclose, 1)
+#     endif
+#   endif
+# endif
+# ifndef __attr_dealloc_fclose
+#  define __attr_dealloc_fclose /* empty */
+# endif
+
 /* Like OPEN_MEMSTREAM, but the stream is wide oriented and produces
    a wide character string.  */
-extern __FILE *open_wmemstream (wchar_t **__bufloc, size_t *__sizeloc) __THROW;
+extern __FILE *open_wmemstream (wchar_t **__bufloc, size_t *__sizeloc) __THROW
+  __attribute_malloc__ __attr_dealloc_fclose;
 #endif
 
 #if defined __USE_ISOC95 || defined __USE_UNIX98