Home/ Questions/Q 7419175
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-29T08:00:54+00:00

Here is my codes: #include <stdio.h> int main() { fopen(./1.txt,r); printf(hello); return 0; }

  • 0

Here is my codes:

#include <stdio.h>
int main()
{
    fopen("./1.txt","r");
    printf("hello");
    return 0;
}

$g++ -g -o m main.cpp

$gdb ./m
(gdb) b fopen
Breakpoint 1 at 0x804842c
(gdb) b printf
Breakpoint 2 at 0x804843c
(gdb) i b
Num     Type           Disp Enb Address    What
1       breakpoint     keep y   0x0804842c <fopen@plt>
2       breakpoint     keep y   0x0804843c <printf@plt>
(gdb) r

it seems that the breakpoint at function fopen never work ,but at printf works fine.
why?

Thanks

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    It’s a bug in GDB, which appears to be fixed in current CVS sources (as of 20120124).

    The problem is that there are two versions of fopen in 32-bit libc.so.6 on Linux, and GDB used to select the wrong one:

    nm -D /lib32/libc.so.6 | grep '\<fopen\>'
0005d0c0 T fopen
00109750 T fopen

readelf -s  /lib32/libc.so.6 | egrep '0005d0c0|00109750'
181: 0005d0c0    50 FUNC    GLOBAL DEFAULT   12 fopen@@GLIBC_2.1
182: 00109750   136 FUNC    GLOBAL DEFAULT   12 fopen@GLIBC_2.0
679: 0005d0c0    50 FUNC    GLOBAL DEFAULT   12 _IO_fopen@@GLIBC_2.1
680: 00109750   136 FUNC    GLOBAL DEFAULT   12 _IO_fopen@GLIBC_2.0

    If you also break on main, and repeat info break, you’ll see that GDB set the breakpoint on fopen@GLIBC_2.0, but the function that is called is the fopen@@GLIBC_2.1.

    • 0