Question

我正在调试一个大型应用程序，我希望在某个字符串写入std::cerr之前中断。我有办法做到这一点吗？

代码中有很多地方写这个字符串。字符串的格式并不总是

std::cerr << "some error code";

它可能是其他形式，例如

std::cerr << write_error_code();

另请注意，std::cerr正在撰写许多内容，因此我不能仅仅依赖std::cerr。

我对std::cout也有同样的问题，但如果答案也不适用，我会发布另一个问题。

Answer 1

这是我在Linux上做的一个例子。这个例子是用gcc 4.3构建的。

#include <iostream>
#include <stdio.h>
#include <setjmp.h>

void write_error_code()
{
  std::cerr << "some error code";
}

int main()
{
  std::cout << "Start, main()\n";
  std::cerr << "some error code" << std::endl;
  std::cerr << "some error code?" << std::endl;
  std::cerr << "some error code?" << std::endl;
  write_error_code();
  std::cout << "End, main()\n";

  return 0;
}

我看了一下反汇编，发现std::cerr << ""是一个符号名为_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc的函数。
该函数有2个参数：__out和__s。
所以我创建了一个.gdbinit文件：

host: srv2-x64rh5-02, OS: Linux 2.6.18-238.el5>more .gdbinit
file a.out
b _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
commands
silent
if strcmp(__s, "some error code") == 0
  print "Some error code has been given as an arg"
  bt
  c
else
  c
end
end
r
quit

在这里我测试我的程序：

host: srv2-x64rh5-02, OS: Linux 2.6.18-238.el5>gdb -q ./a.out
Reading symbols from /import/home/sergey.kurenkov/src/linux.x64.5.0/tests/test.br_on_std_cerr/a.out...done.
Breakpoint 1 at 0x400710
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x2aaaaaaab000
Start, main()
$1 = "Some error code has been given as an arg"
#0  std::operator<< <std::char_traits<char> > (__out=..., __s=0x400a4c "some error code")
    at /home/zalex/test/gcc_build/x86_64-unknown-linux-gnu/libstdc++-v3/include/ostream:509
#1  0x0000000000400873 in main () at main.cpp:13
some error code
some error code?
some error code?
$2 = "Some error code has been given as an arg"
#0  std::operator<< <std::char_traits<char> > (__out=..., __s=0x400a4c "some error code")
    at /home/zalex/test/gcc_build/x86_64-unknown-linux-gnu/libstdc++-v3/include/ostream:509
#1  0x000000000040084f in write_error_code () at main.cpp:7
#2  0x00000000004008f5 in main () at main.cpp:18
some error codeEnd, main()

Program exited normally.

gdb在将某个字符串写入std：cerr之前中断

1 个答案: