exec part with file + break main
The fork was part was explained at: https://stackoverflow.com/a/377295/895245
Now for the exec:
a.c:
#include <unistd.h>
int main(void) {
execl("./b", "./b", "ab", "cd", (char*)NULL);
return 1;
}
b.c:
#include <stdio.h>
int main(int argc, char **argv ) {
printf("%s\n", argv[0]);
printf("%s\n", argv[1]);
}
Then:
gcc -g a.c -o a
gcc -g b.c -o b
gdb -nh -q a
Now on the interactive session:
Reading symbols from a...done.
(gdb) start
Temporary breakpoint 1 at 0x4004ea: file a.c, line 4.
Starting program: /home/ciro/test/gdb-exec/a
Temporary breakpoint 1, main () at a.c:4
4 execl("./b", "./b", "ab", "cd", (char*)NULL);
(gdb) file b
A program is being debugged already.
Are you sure you want to change the file? (y or n) y
Load new symbol table from "b"? (y or n) y
Reading symbols from b...done.
(gdb) b main
Breakpoint 2 at 0x4004f5: file b.c, line 4.
(gdb) n
Breakpoint 2, main (argc=0, argv=0x7fffffffa570) at b.c:4
4 printf("%s\n", argv[1]);
(gdb) n
process 4877 is executing new program: /home/ciro/test/gdb-exec/b
Breakpoint 2, main (argc=3, argv=0x7fffffffa598) at b.c:4
4 printf("%s\n", argv[1]);
(gdb) n
ab
5 printf("%s\n", argv[2]);
(gdb) n
cd
6 }
(gdb)
You just have to make sure that you go up to the exec before running file, possibly with a b execl, since after that you will be using symbols from the new file.
Tested in Ubuntu 14.04, gdb 7.7.1.
