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Date: Tue, 03 Aug 2004 20:31:00 -0000
From: "v dot haisman at sh dot cvut dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Message-ID: <20040803203120.16865.v.haisman@sh.cvut.cz>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug bootstrap/16865] New: False alarm about use of uninitialized variable breaks bootstrap at -O3
X-Bugzilla-Reason: CC
X-SW-Source: 2004-08/txt/msg00256.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

Bootstrap with -O3 dies with error bellow. It is false alarm about use of
uninitialized variable. With -O2 the warning doesn't trigger.


make[2]: Entering directory `/home/4/wilx/tmp/gcc-head/objdir/gcc'
stage1/xgcc -Bstage1/ -B/home/4/wilx/i386-unknown-freebsd4.10/bin/ -c   -O3 -g
-DIN_GCC   -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes
-pedantic -Wno-long-long -Wno-variadic-macros -Wold-style-definition -Werror
-fno-common   -DHAVE_CONFIG_H    -I. -I. -I../../srcdir/gcc -I../../srcdir/gcc/.
-I../../srcdir/gcc/../include -I../../srcdir/gcc/../libcpp/include
-I../../srcdir/gcc/../libbanshee/libcompat -I../../srcdir/gcc/../libbanshee
-I../../srcdir/gcc/../libbanshee/points-to  ../../srcdir/gcc/loop-iv.c -o loop-iv.o
../../srcdir/gcc/loop-iv.c: In function `simplify_using_initial_values':
../../srcdir/gcc/loop-iv.c:1360: warning: 'lhs' may be used uninitialized in
this function
make[2]: *** [loop-iv.o] Error 1
make[2]: Leaving directory `/home/4/wilx/tmp/gcc-head/objdir/gcc'
make[1]: *** [stage2_build] Error 2
make[1]: Leaving directory `/home/4/wilx/tmp/gcc-head/objdir/gcc'
make: *** [bootstrap] Error 2

I've used this to unbreak the bootstrap:
Index: gcc/loop-iv.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/loop-iv.c,v
retrieving revision 2.13
diff -c -p -r2.13 loop-iv.c
*** gcc/loop-iv.c       27 Jul 2004 07:27:12 -0000      2.13
--- gcc/loop-iv.c       3 Aug 2004 20:22:07 -0000
*************** static void
*** 1357,1363 ****
  simplify_using_assignment (rtx insn, rtx *expr, regset altered)
  {
    rtx set = single_set (insn);
!   rtx lhs, rhs;
    bool ret = false;

    if (set)
--- 1357,1363 ----
  simplify_using_assignment (rtx insn, rtx *expr, regset altered)
  {
    rtx set = single_set (insn);
!   rtx lhs = 0, rhs;
    bool ret = false;

    if (set)

-- 
           Summary: False alarm about use of uninitialized variable breaks
                    bootstrap at -O3
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: bootstrap
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: v dot haisman at sh dot cvut dot cz
                CC: gcc-bugs at gcc dot gnu dot org,v dot haisman at sh dot
                    cvut dot cz
 GCC build triplet: i386-unknown-freebsd4.10
  GCC host triplet: i386-unknown-freebsd4.10
GCC target triplet: i386-unknown-freebsd4.10


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16865