Add __attribute_access_none to disable GCC warnings [BZ #27714]

GCC 11 warns when a pointer to an uninitialized object is passed
to a function that takes a const-qualified argument.  This is done
on the assumption that most such functions read from the object.
For the rare case of a function that doesn't, GCC 11 extends
attribute access to add a new mode called none.

POSIX pthread_setspecific() is one such rare function that takes
a const void* argument but that doesn't read from the object it
points to.  To suppress the -Wmaybe-uninitialized issued by GCC
11 when the address of an uninitialized object is passed to it
(e.g., the result of malloc()), this change #defines
__attr_access_none in cdefs.h and uses the macro on the function
in sysdeps/htl/pthread.h and sysdeps/nptl/pthread.h.

1 files changed, 7 insertions, 1 deletions

diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index 8e244a77cf..11f01f741b 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -592,9 +592,15 @@ _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
    array according to access mode, or at least one element when
    size-index is not provided:
      access (access-mode, <ref-index> [, <size-index>])  */
-#define __attr_access(x) __attribute__ ((__access__ x))
+#  define __attr_access(x) __attribute__ ((__access__ x))
+#  if __GNUC_PREREQ (11, 0)
+#    define __attr_access_none(argno) __attribute__ ((__access__ (__none__, argno)))
+#  else
+#    define __attr_access_none(argno)
+#  endif
 #else
 #  define __attr_access(x)
+#  define __attr_access_none(argno)
 #endif
 
 /* Specify that a function such as setjmp or vfork may return