当只有一个观察点时，gdb停止 [英] gdb stops with too many watchpoints when there is only one

问题描述

您知道为什么除了太多的硬件断点/观察点之外无法插入观察点吗？

我有以下调试会话：

  GNU gdb（GDB）7.1 
 ... 
（gdb）watch itrap_t_beg [1] [222] 
硬件观察点1：itrap_t_beg [1] [222] 
（gdb）cont 
继续。 
 ... 
硬件观察点1：itrap_t_beg [1] [222] 
 
 ... 
（gdb）cont 
继续。 
警告：
无法插入硬件观察点1. 
无法插入硬件断点：$ b​​ $ b您可能请求太多硬件断点/观察点。 
 
（gdb）信息中断
数字类型显示地址什么
 1 hw监视点保存y itrap_t_beg [1] [222] 
断点已经命中1次
  

正如您所看到的，只有一个观察点，但它不能插入断点。 b
$ b

你知道我该如何解决这个问题吗？

据我所知，商品x86 CPU有四个调试寄存器可用于支持硬件中断/监视。这限制了您可以观看的对象大小。对象对齐也在这里起作用。

尝试将监视范围限制为一个较小的对象，如结构的第一个和最后一个成员对。

Do you know any other reasons why a watchpoint could not be inserted other than too many hardware breakpoints/watchpoints?

I have the following debug session:

GNU gdb (GDB) 7.1
...
(gdb) watch itrap_t_beg[1][222]
Hardware watchpoint 1: itrap_t_beg[1][222]
(gdb) cont
Continuing.
...
Hardware watchpoint 1: itrap_t_beg[1][222]

...
(gdb) cont
Continuing.
Warning:
Could not insert hardware watchpoint 1.
Could not insert hardware breakpoints:
You may have requested too many hardware breakpoints/watchpoints.

(gdb) info break
Num     Type           Disp Enb Address            What
1       hw watchpoint  keep y                      itrap_t_beg[1][222]
        breakpoint already hit 1 time

As you can see, there's only one watchpoint yet it can't insert the breakpoint.

Do you know how can I fix this?

解决方案

As far as I know commodity x86 CPUs have four debug registers available for supporting hardware breaks/watches. This limits the object size that you can watch. Object alignment also plays here.

Try limiting the watch scope to a smaller object like pair of first and last members of the structure.

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