From: Luis Machado <luis.machado@linaro.org>
To: 杨已彪 <yangyibiao@hust.edu.cn>, gdb@sourceware.org
Subject: Re: Wrong debug info for argc at -O2
Date: Mon, 22 Jun 2020 15:53:15 -0300 [thread overview]
Message-ID: <c3044feb-d401-5120-17d7-999f1bd86477@linaro.org> (raw)
In-Reply-To: <545669ad.7ac1.172612844b0.Coremail.yangyibiao@hust.edu.cn>
On 5/29/20 12:58 PM, 杨已彪 wrote:
>
>
> 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)
What architecture is this?
If you want precise debug information, you should use -O0 instead. With
O2 you are likely to run into situations where the debug info has been
lost or is just incorrect.
With that said, GCC has improved over the past few years in terms of
debug info generation for O2+.
next prev parent reply other threads:[~2020-06-22 18:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 15:58 杨已彪
2020-06-22 18:14 ` Simon Marchi
2020-06-22 18:53 ` Luis Machado [this message]
2020-06-30 15:30 ` 杨已彪
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