Why does the print command in gdb return \035 for C++ std::strings?

Question

Say I have the code:

std::string str = "random";

function(str);

void function (std::string str)
{
  std::cout << str << std::endl;
}

If I step through this code in gdb and then go into the function and do p str it would print out something like this \362\241 but the cout will print to the screen the correct string random. Has anyone seen this before if so what should I do? Am I using the print command wrong in gdb or does it have something to do with how the compiler interprets the string?

Answer 1

GDB is probably missing debug information for the STL for whatever reason. Using Employed Russian's example with g++ (GCC) 4.3.4 20090804 (release) 1 and GNU gdb 6.8.0.20080328-cvs (cygwin-special), I get the following output:

(gdb) p str
$1 = {static npos = <optimized out>,
  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<
No data fields>}, <No data fields>}, _M_p = 0x28cce8 "$▒▒"}}

Which is an interpretation of the raw data fields in std::string. To get the actual string data, I have to reinterpret the _M_p field as a pointer:

(gdb) p *(char**)str._M_dataplus._M_p
$2 = 0xd4a224 "random"

Answer 2

gdb is probably just showing you the byte-string-interpretation of the string class' internals. Try this to verify/work around:

$ print str.c_str()