c++ - GDB:如何将内存地址转换为STL对象

Question

我正在使用GDB分析核心转储。我知道它指向“std::basic_fstream >”的内存地址。
如何在GDB提示符下将原始内存地址转换为该模板对象？
我尝试通过以下命令:
(gdb)p *('std::basic_fstream >'*)0x7fae3800b280
在当前上下文中没有符号“std::basic_fstream >”。
(gdb)p *(std::basic_fstream > *)0x7fae3800b280
表达式中语法错误，在`)0x7fae3800b280'附近。

Answer 1

I tried by below command:

大胆猜测:您的set auto-solib-add off中是否有~/.gdbinit？
以下示例对我来说效果很好:

cat t.cc
#include <fstream>

int main(int argc, char *argv[])
{
  std::wfstream s("/dev/tty", s.out);
  for (int j = 0; j < argc; j++)
    s << j << " " << argv[j] << std::endl;
  return 0;
}

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

(gdb) b 8
Breakpoint 1 at 0x1235: file t.cc, line 8.
(gdb) run foo
Starting program: /tmp/a.out foo
0 /tmp/a.out
1 foo

Breakpoint 1, main (argc=2, argv=0x7fffffffdc28) at t.cc:8
8         return 0;
(gdb) set print static off

(gdb) p s
$1 = {<std::basic_iostream<wchar_t, std::char_traits<wchar_t> >> = {<std::basic_istream<wchar_t, std::char_traits<wchar_t> >> = {<std::basic_ios<wchar_t, std::char_traits<wchar_t> >> = ...

(gdb) p &s
$2 = (std::wfstream *) 0x7fffffffd900

(gdb) p *('std::basic_fstream<wchar_t, std::char_traits<wchar_t> >' *)0x7fffffffd900
$3 = {<std::basic_iostream<wchar_t, std::char_traits<wchar_t> >> = {<std::basic_istream<wchar_t, std::char_traits<wchar_t> >> = {<std::basic_ios<wchar_t, std::char_traits<wchar_t> >> = {<std::ios_base> = ...

您应该尝试复制上述输出。
如果可以重现它，则您的工具将按预期工作，并且您需要集中精力分析core转储。
如果上面的示例无法按预期工作，则说明您的工具链某些部分行为不当或配置错误。
我能够获得No symbol结果的一种方法是通过设置auto-solib-add off:

gdb -q ./a.out
Reading symbols from ./a.out...

(gdb) b 8
Breakpoint 1 at 0x1235: file t.cc, line 8.
(gdb) set auto-solib-add off
(gdb) run
Starting program: /tmp/a.out
0 /tmp/a.out

Breakpoint 1, main (argc=1, argv=0x7fffffffdc28) at t.cc:8
8         return 0;

(gdb) p &s
$1 = (std::wfstream *) 0x7fffffffd900

(gdb) p *('std::basic_fstream<wchar_t, std::char_traits<wchar_t> >' *) 0x7fffffffd900
No symbol "std::basic_fstream<wchar_t, std::char_traits<wchar_t> >" in current context.