From: 杨已彪 <yangyibiao@hust.edu.cn>
To: gdb@sourceware.org
Subject: Wrong debug info for argc at -O2
Date: Fri, 29 May 2020 23:58:48 +0800 (GMT+08:00) [thread overview]
Message-ID: <545669ad.7ac1.172612844b0.Coremail.yangyibiao@hust.edu.cn> (raw)
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;
}
...
Stepping with step and print the values of arguments:
...
$ 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 with step, the value of argc is changed to -8454.
However, When stepping with stepi, the value of argc is still 1 at line 6.
I am posting it here as I am not sure whether this is a gcc bug or a gdb bug.
By the way, I found it very difficult to determine whether a problem is caused by gdb or gcc?
Is there any suggestions?
***************************************/
$ 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.
$ 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.
next reply other threads:[~2020-05-29 15:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 15:58 杨已彪 [this message]
2020-06-22 18:14 ` Simon Marchi
2020-06-22 18:53 ` Luis Machado
2020-06-30 15:30 ` 杨已彪
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