[PATCH v3] xmalloc: Fix warnings with gcc analyzer

[Siddhesh Poyarekar via Libc-alpha <libc-alpha@sourceware.org>]

Tell the compiler that xmalloc family of allocators always return
non-NULL.  xrealloc in locale/programs also always returns non-NULL,
but that conflicts with default realloc behaviour and that of xrealloc
in libsupport, so keep it as is for now and resolve the differences
later.
---
 include/programs/xmalloc.h |  9 ++++++---
 misc/sys/cdefs.h           | 10 ++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/programs/xmalloc.h b/include/programs/xmalloc.h
index 33871e22ef..5dc6aac57b 100644
--- a/include/programs/xmalloc.h
+++ b/include/programs/xmalloc.h
@@ -23,11 +23,14 @@
 
 /* Prototypes for a few program-wide used functions.  */
 extern void *xmalloc (size_t n)
-  __attribute_malloc__ __attribute_alloc_size__ ((1)) __attr_dealloc_free;
+  __attribute_malloc__ __attribute_alloc_size__ ((1)) __attr_dealloc_free
+  __returns_nonnull;
 extern void *xcalloc (size_t n, size_t s)
-  __attribute_malloc__ __attribute_alloc_size__ ((1, 2)) __attr_dealloc_free;
+  __attribute_malloc__ __attribute_alloc_size__ ((1, 2)) __attr_dealloc_free
+  __returns_nonnull;
 extern void *xrealloc (void *o, size_t n)
   __attribute_malloc__ __attribute_alloc_size__ ((2)) __attr_dealloc_free;
-extern char *xstrdup (const char *) __attribute_malloc__ __attr_dealloc_free;
+extern char *xstrdup (const char *) __attribute_malloc__ __attr_dealloc_free
+  __returns_nonnull;
 
 #endif /* xmalloc.h */
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index 30a621ab8f..e490fc1aeb 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -330,6 +330,16 @@
 # define __nonnull(params) _GL_ATTRIBUTE_NONNULL (params)
 #endif
 
+/* The returns_nonnull function attribute marks the return type of the function
+   as always being non-null.  */
+#ifndef __returns_nonnull
+# if __GNUC_PREREQ (4, 9) || __glibc_has_attribute (__returns_nonnull__)
+# define __returns_nonnull __attribute__ ((__returns_nonnull__))
+# else
+# define __returns_nonnull
+# endif
+#endif
+
 /* If fortification mode, we warn about unused results of certain
    function calls which can lead to problems.  */
 #if __GNUC_PREREQ (3,4) || __glibc_has_attribute (__warn_unused_result__)
-- 
2.31.1