gdb, break vs tbreak and watchpoint

Can anyone tell me what's the difference between break and tbreak regarding watchpoints ?

A have a simple test code :

#include <stdlib.h>
#include <stdio.h>

int main(int argc, char **argv) {
  int toto;
  toto = 1;
  toto = 2;
  toto = 3;
  return (EXIT_SUCCESS);
}

When i use break on main(), then watch, toto seem to switch from 0 to 2 :

(gdb) break main
Breakpoint 1 at 0x804839a: file pp.c, line 6.
(gdb) r
Starting program: /mnt/mega20/SRC/C/gdb/pp 

Breakpoint 1, main (argc=1, argv=0xbffff4f4) at pp.c:6
6         toto = 1;
(gdb) watch toto 
Hardware watchpoint 2: toto
(gdb) c
Continuing.
Hardware watchpoint 2: toto

Old value = 0
New value = 2
main (argc=1, argv=0xbffff4f4) at pp.c:8
8         toto = 3;
(gdb)

But when i use tbreak, watc开发者_如何学JAVAh seem to work :

(gdb) tbreak main 
Temporary breakpoint 1 at 0x804839a: file pp.c, line 6.
(gdb) r
Starting program: /mnt/mega20/SRC/C/gdb/pp 

Temporary breakpoint 1, main (argc=1, argv=0xbffff4f4) at pp.c:6
6         toto = 1;
(gdb) watch toto 
Hardware watchpoint 2: toto
(gdb) c
Continuing.
Hardware watchpoint 2: toto

Old value = 0
New value = 1
main (argc=1, argv=0xbffff4f4) at pp.c:7
7         toto = 2;
(gdb) c
Continuing.
Hardware watchpoint 2: toto

Old value = 1
New value = 2
main (argc=1, argv=0xbffff4f4) at pp.c:8
8         toto = 3;
(gdb)

Same results with the start command, it works.

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I suggest you to read this:

Breakpoints and Watchpoints