From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 5516 invoked by alias); 24 Mar 2011 12:15:08 -0000 Received: (qmail 5216 invoked by uid 55); 24 Mar 2011 12:14:52 -0000 Date: Thu, 24 Mar 2011 12:18:00 -0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/48267] incorrect signed overflow warning when a pointer cannot possibly overflow X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Keywords: diagnostic X-Bugzilla-Severity: minor X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Keywords Status Last reconfirmed Component Ever Confirmed Known to fail Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-03/txt/msg02540.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48267 Richard Guenther changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic Status|UNCONFIRMED |NEW Last reconfirmed| |2011.03.24 12:14:46 Component|c |middle-end Ever Confirmed|0 |1 Known to fail| |4.5.2, 4.7.0 --- Comment #1 from Richard Guenther 2011-03-24 12:14:46 UTC --- Confirmed. Happens from #1 0x00000000007307e7 in fold_undefer_overflow_warnings (issue=1 '\001', stmt=0x7ffff5b373c0, code=2) at /space/rguenther/src/svn/trunk/gcc/fold-const.c:281 281 warning_at (locus, OPT_Wstrict_overflow, "%s", warnmsg); (gdb) #2 0x0000000000afdfdf in evaluate_stmt (stmt=0x7ffff5b373c0) at /space/rguenther/src/svn/trunk/gcc/tree-ssa-ccp.c:2117 2117 fold_undefer_overflow_warnings (is_constant, stmt, 0); (gdb) #3 0x0000000000aff7c5 in visit_cond_stmt (stmt=0x7ffff5b373c0, taken_edge_p=0x7fffffffda48) at /space/rguenther/src/svn/trunk/gcc/tree-ssa-ccp.c:2443 2443 val = evaluate_stmt (stmt); (gdb) #4 0x0000000000aff8f8 in ccp_visit_stmt (stmt=0x7ffff5b373c0, taken_edge_p=0x7fffffffda48, output_p=0x7fffffffda40) at /space/rguenther/src/svn/trunk/gcc/tree-ssa-ccp.c:2501 2501 return visit_cond_stmt (stmt, taken_edge_p); (gdb) call debug_gimple_stmt (stmt) if (p_1 < &head_table[1]) which calls fold_binary with &head_table < &head_table[1] and in the end warns here: 8688 if (code != EQ_EXPR 8689 && code != NE_EXPR 8690 && bitpos0 != bitpos1 8691 && (pointer_may_wrap_p (base0, offset0, bitpos0) 8692 || pointer_may_wrap_p (base1, offset1, bitpos1))) 8693 fold_overflow_warning (("assuming pointer wraparound does not " 8694 "occur when comparing P +- C1 with " 8695 "P +- C2"), 8696 WARN_STRICT_OVERFLOW_CONDITIONAL) because we call pointer_may_wrap_p with base0 which isn't an address but an object which is bogus. It's argument has to depend on indirect_base in which case we stripped an ADDR_EXPR.