Question

Is it possible to get the gdb debugger to work with gcc-style nested functions? If so, what versions of gcc/gdb are needed?

Answer 1

It appears that gcc/gdb have got the hang of it. With earlier versions it just didn’t work, but here’s a transcript of a simple session:

jla@jla-desktop$ gdb --version
GNU gdb (GDB) Fedora (7.2-51.fc14)
Copyright (C) 2010 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.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
~
jla@jla-desktop$ gcc --version
gcc (GCC) 4.5.1 20100924 (Red Hat 4.5.1-4)
Copyright (C) 2010 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.

~
jla@jla-desktop$ cat hello.c
#include<stdio.h>

void main(void)
{
    char* hello="hello";
    int sub(int a){
        int b;
        int c;
        b=a;
        a++;
        c=a;
        return a+b+c;
    }

    printf("%s(%i)\n", hello, sub(3));
}

~
jla@jla-desktop$ gcc -ggdb3 hello.c -o hello
~
jla@jla-desktop$ gdb hello
GNU gdb (GDB) Fedora (7.2-51.fc14)
Copyright (C) 2010 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.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/jla/hello...done.
(gdb) b main
Breakpoint 1 at 0x80483f1: file hello.c, line 5.
(gdb) list
1   #include<stdio.h>
2   
3   void main(void)
4   {
5       char* hello="hello";
6       int sub(int a){
7           int b;
8           int c;
9           b=a;
10          a++;
(gdb) r
Starting program: /home/jla/hello 

Breakpoint 1, main () at hello.c:5
5       char* hello="hello";
Missing separate debuginfos, use: debuginfo-install glibc-2.13-2.i686
(gdb) info locals
hello = 0x7aeff4 "|\355z"
(gdb) s
15      printf("%s(%i)\n", hello, sub(3));
(gdb) s
sub (a=3) at hello.c:9
9           b=a;
(gdb) info locals
b = 134518388
c = 0
(gdb) p a
$1 = 3
(gdb) p b
$2 = 134518388
(gdb) p c
$3 = 0
(gdb) where
#0  sub (a=3) at hello.c:9
#1  0x08048405 in main () at hello.c:15
(gdb)