Finish And Until
'finish' lets the current function execute until it finishes.
'until <source line> makes gdb continue program execution until the given line is reached.
Note: 'until' can only be executed if the program already
return
Sometimes we want a function to terminate prematurely during a debugging session.
For example:
A function computes a variable's value wrongly.
We found this, but still want to debug the rest of the program.
we can force the function to return immediately with the correct value:
return 59
Conditional Break-Points
Let us suppose we have a long loop, and we want to start debugging only at the 503rd iteration.
We do this using conditional break-points:
Breakpoint 1, func_long_calc (i=5000) at c1.c:5
5 int j = 5;
(gdb) list 8,10
8 for (plastic = 0; plastic < i; ++plastic) {
9 j += plastic;
10 }
(gdb) break 9 if plastic == 503
Breakpoint 4 at 0x804835a: file c1.c, line 9.
(gdb) cont
Continuing.
Breakpoint 4, func_long_calc (i=5000) at c1.c:9
9 j += plastic;
(gdb) print plastic
$1 = 503
Other Break-Point Commands
表达式匹配断点
'rbreak <regular expression>' sets break-points for all functions whose name matches the regular expression.
'disable <number>' disables (but does not delete) the given break-point.
'enable <number>' re-enables the given (previously disabled) break-point.
临时断点
'tbreak' sets a temporary break-point - once it is hit, it is deleted.
监测点
Watch-Points
定义
A watch-point makes the program stop when an expression is true, regardless of the function in which it happens.
例1
A basic example: 'watch a == 1' makes the program stop when variable 'a' has the value... '1'.
例2
Checking when my memory gets over-written with a zero byte:
watch *(char*)0x65476 == 0
查看
Watch-points and other break-points are all seen using 'info break' or 'info watch'.
删除
use 'delete <watch-point number>' to delete a watch-point, just like with a break-point.
Hardware Vs. Software Watch-Points
By default, gdb attempts to use hardware-assisted break-points.
These get processed using the hardware, and have a lesser impact on program speed...
...relative to software watch-points.
There are a few other caveats to watch-points regarding multi-threaded programs - we'll see them later.
I Want To Do This - Again!
You can ask gdb to save a "checkpoint": （恢复点）
checkpoint
reference: http://www.haifux.org/lectures/210/index.html
more time!
After stepping forward and finding you've gone further then you wanted, switch back to the checkpoint:
restart <checkpoint id> （返回恢复点）
To see the list of active check-points:
info checkpoints （查看恢复点)
What a checkpoint does: forks off a copy of the program, so gdb will be able to switch back to it later on.
To delete checkpoints:
delete checkpoint <checkpoint id> (删除恢复点)