https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89463
Bug ID: 89463
Summary: gcc generates wrong debug information at -O3
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: qrzhang at gatech dot edu
Target Milestone: ---
It bug affects the latest trunk.
It also affects gcc-8 and gcc-7.
gcc-6 works fine.
With "-O3", it incorrectly prints "i=0".
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/9.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 9.0.1 20190222 (experimental) [trunk revision 269113] (GCC)
$ cat abc.c
int a;
int main() {
int i;
for (; a < 10; a++)
i = 0;
for (; i < 6; i++)
;
optimize_me_not();
}
$ cat outer.c
optimize_me_not() {}
$ cat cmds
b 8
r
p i
kill
q
$ gcc-trunk -g abc.c outer.c
$ gdb-trunk -x cmds -batch a.out
Breakpoint 1 at 0x4004b9: file abc.c, line 8.
Breakpoint 1, main () at abc.c:8
8 optimize_me_not();
$1 = 6
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
[Inferior 1 (process 29883) killed]
$ gcc-trunk -g abc.c outer.c -O3
$ gdb-trunk -x cmds -batch a.out
Breakpoint 1 at 0x4003b7: file abc.c, line 8.
Breakpoint 1, main () at abc.c:8
8 optimize_me_not();
$1 = 0
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
[Inferior 1 (process 31868) killed]
