[glibc] posix: Suppress -Os may be used uninitialized warnings on regexec

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=442e3a21724b07b3ae1c3c5eeba4a8e44a1a50a3

commit 442e3a21724b07b3ae1c3c5eeba4a8e44a1a50a3
Author: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Date:   Wed Sep 21 10:51:05 2022 -0300

    posix: Suppress -Os may be used uninitialized warnings on regexec
    
    GCC with -Os issues may uninitialized warnings on regexec code.
    
    Checked on x86_64-linux-gnu and i686-linux-gnu.
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>
    Tested-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 posix/regexec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/posix/regexec.c b/posix/regexec.c
index cffeaf2845..386a757f35 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -3768,7 +3768,13 @@ check_node_accept_bytes (const re_dfa_t *dfa, Idx node_idx,
 	      _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
 	  for (i = 0; i < cset->ncoll_syms; ++i)
 	    {
+	      /* The compiler might warn that extra may be used uninitialized,
+		 however the loop will be executed iff ncoll_syms is larger
+		 than 0,which means extra will be already initialized.  */
+	      DIAG_PUSH_NEEDS_COMMENT;
+	      DIAG_IGNORE_Os_NEEDS_COMMENT (8, "-Wmaybe-uninitialized");
 	      const unsigned char *coll_sym = extra + cset->coll_syms[i];
+	      DIAG_POP_NEEDS_COMMENT;
 	      /* Compare the length of input collating element and
 		 the length of current collating element.  */
 	      if (*coll_sym != elem_len)