- gdb 工具 display，執行每一步驟都看變數 b 的值。
[dywang@dyH gcc]$ gdb -q gdbtest1
Reading symbols from gdbtest1...done.
(gdb) l
1 int main()
2 {
3 int a, b, c;
4 a=5;
5 b=10;
6 b+=a;
7 c=b+a;
8 return 0;
9 }
(gdb) b 2
Breakpoint 1 at 0x400478: file gdbtest1.c, line 2.
(gdb) r
Starting program: gdbtest1
Breakpoint 1, main () at gdbtest1.c:4
4 a=5;
(gdb) display b
1: b = 0
(gdb) n
5 b=10;
1: b = 0
(gdb) n
6 b+=a;
1: b = 10
(gdb) n
7 c=b+a;
1: b = 15
(gdb) n
8 return 0;
1: b = 15
(gdb) n
9 }
1: b = 15
(gdb) c
Continuing.
Program exited normally.
(gdb) q
- 重新執行 gdb 工具，使用指令 info 查看狀況，目前沒有變數 display，有一個中斷點。
[dywang@dyH gcc]$ gdb -q gdbtest1
Reading symbols from gdbtest1...done.
(gdb) b 2
Breakpoint 1 at 0x400478: file gdbtest1.c, line 2.
(gdb) r
Starting program: gdbtest1
Breakpoint 1, main () at gdbtest1.c:4
4 a=5;
(gdb) info display
There are no auto-display expressions now.
(gdb) info break
Num Type Disp Enb Address What
1 breakpoint keep y 0x0000000000400478 in main at gdbtest1.c:2
breakpoint already hit 1 time
- 產生變數 a 的 display，並用 info 查看狀況為 enable。
(gdb) display a
1: a = 32767
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
1: y a
- disable 變數 a 的 display，再用 info 查看狀況為 disable。
(gdb) disable display 1
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
1: n a
- disable 中斷點 1，再用 info 查看狀況為 disable。
(gdb) disable break 1
(gdb) info break
Num Type Disp Enb Address What
1 breakpoint keep n 0x0000000000400478 in main at gdbtest1.c:2
breakpoint already hit 1 time
- 增加變數 b 與 c 的 display
(gdb) display b
2: b = 0
(gdb) display c
3: c = 0
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
3: y c
2: y b
1: n a
- enable 變數 a 的 display
(gdb) enable display 1
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
3: y c
2: y b
1: y a
- 繼續下一步， a, b, c 三個變數的值皆 display
(gdb) n
5 b=10;
3: c = 0
2: b = 0
1: a = 5
- delete 變數的 display
(gdb) delete display 1
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
3: y c
2: y b
(gdb) delete display 2
(gdb) info display
Auto-display expressions now in effect:
Num Enb Expression
3: y c
