[glibc/release/2.36/master] locale: prevent maybe-uninitialized errors with -Os [BZ #19444]

[glibc/release/2.36/master] locale: prevent maybe-uninitialized errors with -Os [BZ #19444]

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4444be051cae74fed390d4bc1a15ed730cc07b02

commit 4444be051cae74fed390d4bc1a15ed730cc07b02
Author: Martin Jansa <Martin.Jansa@gmail.com>
Date:   Wed Sep 21 10:51:03 2022 -0300

    locale: prevent maybe-uninitialized errors with -Os [BZ #19444]
    
    Fixes following error when building  with -Os:
    | In file included from strcoll_l.c:43:
    | strcoll_l.c: In function '__strcoll_l':
    | ../locale/weight.h:31:26: error: 'seq2.back_us' may be used
    uninitialized in this function [-Werror=maybe-uninitialized]
    |    int_fast32_t i = table[*(*cpp)++];
    |                           ^~~~~~~~~
    | strcoll_l.c:304:18: note: 'seq2.back_us' was declared here
    |    coll_seq seq1, seq2;
    |                   ^~~~
    | In file included from strcoll_l.c:43:
    | ../locale/weight.h:31:26: error: 'seq1.back_us' may be used
    uninitialized in this function [-Werror=maybe-uninitialized]
    |    int_fast32_t i = table[*(*cpp)++];
    |                           ^~~~~~~~~
    | strcoll_l.c:304:12: note: 'seq1.back_us' was declared here
    |    coll_seq seq1, seq2;
    |             ^~~~
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>
    Tested-by: Carlos O'Donell <carlos@redhat.com>
    
    (cherry picked from commit c651f9da530320e9939e6cbad57b87695eeba41c)

Diff:
---
 locale/weight.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/locale/weight.h b/locale/weight.h
index 8be2d220f8..4a4d5aa6b2 100644
--- a/locale/weight.h
+++ b/locale/weight.h
@@ -27,7 +27,14 @@ findidx (const int32_t *table,
 	 const unsigned char *extra,
 	 const unsigned char **cpp, size_t len)
 {
+  /* With GCC 8 when compiling with -Os the compiler warns that
+     seq1.back_us and seq2.back_us might be used uninitialized.
+     This uninitialized use is impossible for the same reason
+     as described in comments in locale/weightwc.h.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_Os_NEEDS_COMMENT (8, "-Wmaybe-uninitialized");
   int32_t i = table[*(*cpp)++];
+  DIAG_POP_NEEDS_COMMENT;
   const unsigned char *cp;
   const unsigned char *usrc;