Fix two more -Os strcoll / wcscoll build failures

[Joseph Myers <joseph@codesourcery.com>]

Continuing fixes for -Os build issues shown with build-many-glibcs.py,
this patch adds uses of DIAG_* to disable -Wmaybe-uninitialized in two
more places where code inlined from strcoll / wcscoll is wrongly
diagnosed as possibly using uninitialized structure fields.  (All
these warnings in different places for these functions are I think
essentially the same bug.)

Tested with build-many-glibcs.py for alpha-linux-gnu and
mips-linux-gnu that this fixes the -Os build failures for those
configurations with GCC 7.

2018-02-26  Joseph Myers  <joseph@codesourcery.com>

	* locale/weightwc.h (findidx): Ignore -Wmaybe-uninitialized for
	-Os in two more places.

diff --git a/locale/weightwc.h b/locale/weightwc.h
index ac25ba9..36c65b5 100644
--- a/locale/weightwc.h
+++ b/locale/weightwc.h
@@ -28,7 +28,15 @@ findidx (const int32_t *table,
 	 const wint_t *extra,
 	 const wint_t **cpp, size_t len)
 {
+  /* With GCC 7 when compiling with -Os the compiler warns that
+     seq1.back_us and seq2.back_us, which become *cpp, might be used
+     uninitialized.  This is impossible as this function cannot be
+     called except in cases where those fields have been
+     initialized.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_Os_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
   wint_t ch = *(*cpp)++;
+  DIAG_POP_NEEDS_COMMENT;
   int32_t i = __collidx_table_lookup ((const char *) table, ch);
 
   if (i >= 0)
@@ -107,11 +115,18 @@ findidx (const int32_t *table,
 	      continue;
 	    }
 
+	  /* With GCC 7 when compiling with -Os the compiler warns
+	     that seq1.back_us and seq2.back_us, which become usrc,
+	     might be used uninitialized.  This is impossible for the
+	     same reason as described above.  */
+	  DIAG_PUSH_NEEDS_COMMENT;
+	  DIAG_IGNORE_Os_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
 	  if (cp[nhere - 1] > usrc[nhere -1])
 	    {
 	      cp += 2 * nhere;
 	      continue;
 	    }
+	  DIAG_POP_NEEDS_COMMENT;
 
 	  if (cp[2 * nhere - 1] < usrc[nhere -1])
 	    {

-- 
Joseph S. Myers
joseph@codesourcery.com