gdb、break 与 tbreak 和观察点

Question

谁能告诉我关于观察点的break和tbreak之间有什么区别？

A 有一个简单的测试代码：

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

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

当我在 main() 上使用 break，然后 watch，toto 似乎从 0 切换到 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)

但是当我使用 tbreak 时，watch 似乎工作：

(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)

与 start 命令的结果相同，它工作。