[PATCH 1/6] locale: prevent maybe-uninitialized errors with -Os [BZ #19444]

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

From: Martin Jansa <Martin.Jansa@gmail.com>

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;
|             ^~~~
---
 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;
 
-- 
2.34.1