Date: Tue, 13 Mar 2007 15:11:07 +0300 From: Andrey Chernov <ache@freebsd.org> To: current@freebsd.org Subject: Bad gcc -O optimization cause core dump. What to do? Message-ID: <20070313121106.GA96293@nagual.pp.ru>
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Copy the segment below to the file a.c
---------------------- cut me here ---------------------
#include <stdio.h>
main() {
printf("%s\n", NULL);
}
---------------------- cut me here ---------------------
Compile first as
cc a.c
./a.out
got
(null)
Then compile as
cc -O a.c
./a.out
got core dump.
Lets see assembler output from
cc -O -S a.c
.file "a.c"
.text
.p2align 2,,3
.globl main
.type main, @function
main:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
subl $28, %esp
pushl $0
call puts
leave
ret
.size main, .-main
.ident "GCC: (GNU) 3.4.6 [FreeBSD] 20060825"
It calls "puts(NULL)" with core dump.
It means "printf("%s\n", NULL)" is overoptimized.
BTW, things like "printf("1%s\n", NULL)" are not overoptimized.
Any ideas? Is it right or needs to be fixed?
--
http://ache.pp.ru/
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