https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95414
Bug ID: 95414
Summary: Wrong debug info for argc at -O2
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: yangyibiao at hust dot edu.cn
Target Milestone: ---
Created attachment 48633
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48633&action=edit
a.out
$ gcc --version
gcc (GCC) 10.0.1 20200419 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
yibiao:~/Debugger$ gdb --version
GNU gdb (GDB) 10.0.50.20200517-git
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Consider test-case:
...
$ cat small.c
#include <stdio.h>
int main(int argc, char **argv) {
char buf[6];
char c[] = "abc";
sprintf(buf, (char *)c, 1);
return 0;
}
...
$ gcc -O2 -g small.c; gdb -q a.out
Reading symbols from a.out...
(gdb) b main
Breakpoint 1 at 0x401040: file small.c, line 5.
(gdb) r
Starting program: /home/yibiao/Debugger/a.out
Breakpoint 1, main (argc=1, argv=0x7fffffffdff8) at small.c:5
5 char c[] = "abc";
(gdb) info args argc
argc = 1
(gdb) step
6 sprintf(buf, (char *)c, 1);
(gdb) info args argc
argc = -8454
(gdb)
/**************************************
We can find that at line 5, the value of argc is 1. When stepping to line 6,
the value of argc is changed to -8454. When stepping with stepi, the value of
argc is correct.
