From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30072 invoked by alias); 3 May 2012 19:50:44 -0000 Received: (qmail 30063 invoked by uid 22791); 3 May 2012 19:50:43 -0000 X-SWARE-Spam-Status: No, hits=-3.5 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,TW_VF X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 03 May 2012 19:50:30 +0000 From: "ppluzhnikov at google dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/53220] New: g++ mis-compiles compound literals Date: Thu, 03 May 2012 19:50:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: ppluzhnikov at google dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: 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: 2012-05/txt/msg00328.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53220 Bug #: 53220 Summary: g++ mis-compiles compound literals Classification: Unclassified Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: ppluzhnikov@google.com This appears to be a gcc-4.7 regression. Confirmed in: g++ (GCC) 4.8.0 20120331 (experimental) g++ (GCC) 4.8.0 20120503 (experimental) #include int main() { for (int *p = (int[]){ 1, 2, 3, 0}; *p; ++p) { printf("%d\n", *p); } return 0; } gcc -std=c99 t2.c && ./a.out 1 2 3 gcc -std=c99 -O2 t2.c && ./a.out 1 2 3 g++ t2.c && ./a.out 1 2 3 g++ -O2 -g t2.c && ./a.out 944127552 32767 AFAICT, g++ completely removes the initializer and reads random garbage off stack: (gdb) disas main Dump of assembler code for function main(): 0x0000000000400600 <+0>: push %rbx 0x0000000000400601 <+1>: sub $0x10,%rsp 0x0000000000400605 <+5>: mov (%rsp),%esi 0x0000000000400608 <+8>: mov %rsp,%rbx 0x000000000040060b <+11>: test %esi,%esi 0x000000000040060d <+13>: je 0x400626 0x000000000040060f <+15>: nop 0x0000000000400610 <+16>: xor %eax,%eax 0x0000000000400612 <+18>: add $0x4,%rbx 0x0000000000400616 <+22>: mov $0x40071c,%edi 0x000000000040061b <+27>: callq 0x400478 0x0000000000400620 <+32>: mov (%rbx),%esi 0x0000000000400622 <+34>: test %esi,%esi 0x0000000000400624 <+36>: jne 0x400610 0x0000000000400626 <+38>: add $0x10,%rsp 0x000000000040062a <+42>: xor %eax,%eax 0x000000000040062c <+44>: pop %rbx 0x000000000040062d <+45>: retq End of assembler dump. valgrind ./a.out ... ==13572== Conditional jump or move depends on uninitialised value(s) ==13572== at 0x40060D: main (/tmp/t2.c:5) ==13572== ==13572== Use of uninitialised value of size 8 ==13572== at 0x5625E4B: _itoa_word (/build/buildd/eglibc-2.11.1/stdio-common/_itoa.c:195) ==13572== by 0x5628A87: vfprintf (/build/buildd/eglibc-2.11.1/stdio-common/vfprintf.c:1616) ==13572== by 0x5631659: printf (/build/buildd/eglibc-2.11.1/stdio-common/printf.c:35) ==13572== by 0x40061F: main (/tmp/t2.c:6) ==13572== ==13572== Conditional jump or move depends on uninitialised value(s) ==13572== at 0x5625E55: _itoa_word (/build/buildd/eglibc-2.11.1/stdio-common/_itoa.c:195) ==13572== by 0x5628A87: vfprintf (/build/buildd/eglibc-2.11.1/stdio-common/vfprintf.c:1616) ==13572== by 0x5631659: printf (/build/buildd/eglibc-2.11.1/stdio-common/printf.c:35) ==13572== by 0x40061F: main (/tmp/t2.c:6) ==13572== ==13572== Conditional jump or move depends on uninitialised value(s) ==13572== at 0x5627ED2: vfprintf (/build/buildd/eglibc-2.11.1/stdio-common/vfprintf.c:1616) ==13572== by 0x5631659: printf (/build/buildd/eglibc-2.11.1/stdio-common/printf.c:35) ==13572== by 0x40061F: main (/tmp/t2.c:6) ==13572== ==13572== Conditional jump or move depends on uninitialised value(s) ==13572== at 0x5627EF0: vfprintf (/build/buildd/eglibc-2.11.1/stdio-common/vfprintf.c:1616) ==13572== by 0x5631659: printf (/build/buildd/eglibc-2.11.1/stdio-common/printf.c:35) ==13572== by 0x40061F: main (/tmp/t2.c:6) ==13572== -16780368 ==13572== Conditional jump or move depends on uninitialised value(s) ==13572== at 0x400624: main (/tmp/t2.c:5) ==13572== 127 ... Google ref: b/6439133