[glibc] Disable spurious -Warray-bounds for ypclnt.c (bug 26687)

[Joseph Myers <jsm28@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=882774658cb8daee4c16677a3fd674f6052cc157

commit 882774658cb8daee4c16677a3fd674f6052cc157
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri Oct 30 21:40:25 2020 +0000

    Disable spurious -Warray-bounds for ypclnt.c (bug 26687)
    
    Included among the GCC 11 warnings listed in bug 26687, but not fixed
    when that bug was marked as FIXED, are -Warray-bounds warnings in
    nis/ypclnt.c.  These are all for different calls to the same piece of
    code, which already has a comment explaining that the element accessed
    is in a common prefix of the various structures.  On the basis of that
    comment, this patch treats the warning as a false positive and
    disables it for that code.
    
    Tested with build-many-glibcs.py for arm-linux-gnueabi, where,
    together with my previous two patches, this allows the build of glibc
    to complete with GCC 11 (further build failures appear in the
    testsuite).
    
    Reviewed-by: DJ Delorie <dj@redhat.com>

Diff:
---
 nis/ypclnt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/nis/ypclnt.c b/nis/ypclnt.c
index ada08bf982..898f8143e9 100644
--- a/nis/ypclnt.c
+++ b/nis/ypclnt.c
@@ -30,6 +30,7 @@
 #include <sys/uio.h>
 #include <libc-lock.h>
 #include <shlib-compat.h>
+#include <libc-diag.h>
 
 /* This should only be defined on systems with a BSD compatible ypbind */
 #ifndef BINDINGDIR
@@ -368,12 +369,19 @@ do_ypcall_tr (const char *domain, u_long prog, xdrproc_t xargs,
 	      caddr_t req, xdrproc_t xres, caddr_t resp)
 {
   int status = do_ypcall (domain, prog, xargs, req, xres, resp);
+  DIAG_PUSH_NEEDS_COMMENT;
+  /* This cast results in a warning that a ypresp_val is partly
+     outside the bounds of the actual object referenced, but as
+     explained below only the stat element (in a common prefix) is
+     accessed.  */
+  DIAG_IGNORE_NEEDS_COMMENT (11, "-Warray-bounds");
   if (status == YPERR_SUCCESS)
     /* We cast to ypresp_val although the pointer could also be of
        type ypresp_key_val or ypresp_master or ypresp_order or
        ypresp_maplist.  But the stat element is in a common prefix so
        this does not matter.  */
     status = ypprot_err (((struct ypresp_val *) resp)->stat);
+  DIAG_POP_NEEDS_COMMENT;
   return status;
 }