Question

我有一个std :: vector作为类的一部分，它包含一个自定义类型。它的内容似乎从程序的某个地方神秘地改变了。我无法弄清楚这是怎么回事。

有没有办法从gdb“观察”std :: vector的内容（或大小）？

感谢。

Answer 1

有没有办法从gdb“观察”std :: vector的内容（或大小）？

假设您正在使用GCC，请在theVector->_M_impl._M_start和_M_finish上设置观察点。如果您正在使用其他一些std :: vector实现，请相应地进行调整。

示例：

#include <vector>

int main()
{
  std::vector<int> v;

  v.push_back(1);
  v.push_back(2);
}

g++ -g t.cc
gdb -q ./a.out

Reading symbols from /tmp/a.out...done.
(gdb) start
Temporary breakpoint 1 at 0x40090f: file t.cc, line 5.

Temporary breakpoint 1, main () at t.cc:5
5     std::vector<int> v;
(gdb) n
7     v.push_back(1);
(gdb) p v._M_impl._M_start
$1 = (int *) 0x0
(gdb) p v._M_impl._M_finish 
$2 = (int *) 0x0
(gdb) p &v._M_impl._M_finish
$3 = (int **) 0x7fffffffd878
(gdb) watch *$3
Hardware watchpoint 2: *$3
(gdb) p &v._M_impl._M_start
$4 = (int **) 0x7fffffffd870
(gdb) watch *$4
Hardware watchpoint 3: *$4
(gdb) c
Hardware watchpoint 3: *$4

Old value = (int *) 0x0
New value = (int *) 0x604010
std::vector<int, std::allocator<int> >::_M_insert_aux (this=0x7fffffffd870, __position=0x0) at /usr/include/c++/4.4/bits/vector.tcc:365
365       this->_M_impl._M_finish = __new_finish;
(gdb) bt
#0  std::vector<int, std::allocator<int> >::_M_insert_aux (this=0x7fffffffd870, __position=0x0) at /usr/include/c++/4.4/bits/vector.tcc:365
#1  0x0000000000400a98 in std::vector<int, std::allocator<int> >::push_back (this=0x7fffffffd870, __x=@0x7fffffffd88c) at /usr/include/c++/4.4/bits/stl_vector.h:741
#2  0x0000000000400935 in main () at t.cc:7
(gdb) c
Hardware watchpoint 2: *$3

Old value = (int *) 0x0
New value = (int *) 0x604014
std::vector<int, std::allocator<int> >::_M_insert_aux (this=0x7fffffffd870, __position=0x0) at /usr/include/c++/4.4/bits/vector.tcc:366
366       this->_M_impl._M_end_of_storage = __new_start + __len;
(gdb) bt
#0  std::vector<int, std::allocator<int> >::_M_insert_aux (this=0x7fffffffd870, __position=0x0) at /usr/include/c++/4.4/bits/vector.tcc:366
#1  0x0000000000400a98 in std::vector<int, std::allocator<int> >::push_back (this=0x7fffffffd870, __x=@0x7fffffffd88c) at /usr/include/c++/4.4/bits/stl_vector.h:741
#2  0x0000000000400935 in main () at t.cc:7

... etc...

Answer 2

我认为http://sourceware.org/gdb/wiki/STLSupport会有所帮助。

如何在gdb中“观察”C ++ std :: vector的大小？

2 个答案: