fnmatch: work around GCC compiler warning bug with uninit var

* posix/fnmatch_loop.c (FCT): Use a scalar not a one-item array.
This works around a bug with x86-64 GCC 4.9.2 and earlier
where 'gcc -O2 -Wmaybe-uninitialized' incorrectly complains
"../locale/weightwc.h:93:7: warning: '*((void *)&str+4)' may be
used uninitialized in this function [-Wmaybe-uninitialized]".

diff --git a/ChangeLog b/ChangeLog
index 8ee0650..c020ed4 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2014-11-25  Paul Eggert  <eggert@cs.ucla.edu>
+
+       fnmatch: work around GCC compiler warning bug with uninit var
+       * posix/fnmatch_loop.c (FCT): Use a scalar not a one-item array.
+       This works around a bug with x86-64 GCC 4.9.2 and earlier
+       where 'gcc -O2 -Wmaybe-uninitialized' incorrectly complains
+       "../locale/weightwc.h:93:7: warning: '*((void *)&str+4)' may be
+       used uninitialized in this function [-Wmaybe-uninitialized]".
+
 2014-11-25  Joseph Myers  <joseph@codesourcery.com>
 
        * posix/bug-regex31.c (main): Return RES not 0.

diff --git a/posix/fnmatch_loop.c b/posix/fnmatch_loop.c
index db6d9d7..1e27913 100644 (file)
--- a/posix/fnmatch_loop.c
+++ b/posix/fnmatch_loop.c
@@ -343,7 +343,12 @@ FCT (pattern, string, string_end, no_leading_period, flags, ends, alloca_used)
 #ifdef _LIBC
                else if (c == L('[') && *p == L('='))
                  {
-                   UCHAR str[1];
+                   /* It's important that STR be a scalar variable rather
+                      than a one-element array, because GCC (at least 4.9.2
+                      -O2 on x86-64) can be confused by the array and
+                      diagnose a "used initialized" in a dead branch in the
+                      findidx function.  */
+                   UCHAR str;
                    uint32_t nrules =
                      _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
                    const CHAR *startp = p;
@@ -355,7 +360,7 @@ FCT (pattern, string, string_end, no_leading_period, flags, ends, alloca_used)
                        c = L('[');
                        goto normal_bracket;
                      }
-                   str[0] = c;
+                   str = c;
 
                    c = *++p;
                    if (c != L('=') || p[1] != L(']'))
@@ -368,7 +373,7 @@ FCT (pattern, string, string_end, no_leading_period, flags, ends, alloca_used)
 
                    if (nrules == 0)
                      {
-                       if ((UCHAR) *n == str[0])
+                       if ((UCHAR) *n == str)
                          goto matched;
                      }
                    else
@@ -383,7 +388,7 @@ FCT (pattern, string, string_end, no_leading_period, flags, ends, alloca_used)
 # endif
                        const int32_t *indirect;
                        int32_t idx;
-                       const UCHAR *cp = (const UCHAR *) str;
+                       const UCHAR *cp = (const UCHAR *) &str;
 
 # if WIDE_CHAR_VERSION
                        table = (const int32_t *)