stacktrace and functions in namespaces

Question

I am trying to get a backtrace at some point of the execution of my (c++) program.

for that I am using backtrace and backtrace_symbols. Something along this lines:

std::string stacktrace( unsigned int frames_to_skip )
{
    std::string str;

    void* stack_addrs[50];
    int trace_size = backtrace( stack_addrs, 50 );
    char** stack_strings = backtrace_symbols( stack_addrs, trace_size );

    str += "[bt] backtrace:\n";
    // skip frames_to_skip stack frames
    for( int i = frames_to_skip; i < trace_size; ++i )
    {
        char tmp[4096];
        sprintf( tmp, "[bt] #%d %s\n", i-frames_to_skip, stack_strings[i] );
        str += tmp;
    }

    free( stack_strings );

    return str;
}

It works but some functions names are missing. example:

[bt] #0 /path/to/executable() [0x43e1b5]
[bt] #1 /path/to/executable() [0x43e0cd]
[bt] #2 /path/to/executable() [0x43df51]
[bt] #3 /path/to/executable() [0x43dd44]
[bt] #4 /path/to/executable() [0x43db50]
[bt] #5 /path/to/executable() [0x43d847]
[bt] #6 /path/to/executable() [0x43d216]
[bt] #7 /path/to/executable() [0x43c1e1]
[bt] #8 /path/to/executable() [0x43b293]
[bt] #9 /path/to/executable(_Z29SomeRN5other8symbolE+0x2c) [0x43a6ca]
[bt] #10 /path/to/executable(_Z11SomeIN5_8symbolEPFvRS1_EEvRKT_RKT0_+0x77) [0x441716]
...

the functions 0 to 8 have one common point : they all sit in a namespace...
I tried putting function 9 in an anonymous namespace (without any other modification) and it disapears from the backtrace... which now looks like this:

[bt] #0 /path/to/executable() [0x43e1b5]
[bt] #1 /path/to/executable() [0x43e0cd]
[bt] #2 /path/to/executable() [0x43df51]
[bt] #3 /path/to/executable() [0x43dd44]
[bt] #4 /path/to/executable() [0x43db50]
[bt] #5 /path/to/executable() [0x43d847]
[bt] #6 /path/to/executable() [0x43d216]
[bt] #7 /path/to/executable() [0x43c1e1]
[bt] #8 /path/to/executable() [0x43b293]
[bt] #9 /path/to/executable() [0x43a6ca]
[bt] #10 /path/to/executable(_Z11SomeIN5_8symbolEPFvRS1_EEvRKT_RKT0_+0x77) [0x441716]
...

Is there any way to fix that?

p.s.: version of g++: g++ (GCC) 4.6.0 20110530 (Red Hat 4.6.0-9)

edit fixed max depth of the backtrace after Code Monkey remark
edit2 added the full code of the function
edit3 the code is compiled with -O0 -g3 and linked with -rdynamic