How to make gdb show the original non-mangling function name on disassembly model?

Question

void outputString(const char *str) {
  cout << "outputString(const char *str) : " << str << endl;
}

turns out to be

Dump of assembler code for function _Z12outputStringPKc:  
0x004013ee <_Z12outputStringPKc+0>: push   ebp  
0x004013ef <_Z12outputStringPKc+1>: mov    ebp,esp  
0x004013f1 <_Z12outputStringPKc+3>: sub    esp,0x8  
0x004013f4 <_Z12outputStringPKc+6>: mov    DWORD PTR [esp+4],0x443000  
0x004013fc <_Z12outputStringPKc+14>:    mov    DWORD PTR [esp],0x4463c0  
0x00401403 <_Z12outputStringPKc+21>:    call   0x43f6e8  <_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc>  
0x00401408 <_Z12outputStringPKc+26>:    mov    edx,DWORD PTR [ebp+8]  
0x0040140b <_Z12outputStringPKc+29>:    mov    DWORD PTR [esp+4],edx  
0x0040140f <_Z12outputStringPKc+33>:    mov    DWORD PTR [esp],eax  
0x00401412 <_Z12outputStringPKc+36>:    call  0x43f6e8 <_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc>  
0x00401417 <_Z12outputStringPKc+41>:    mov    DWORD PTR [esp+4],0x43e4c8  
0x0040141f <_Z12outputStringPKc+49>:    mov    DWORD PTR [esp],eax  
0x00401422 <_Z12outputStringPKc+52>:    call   0x42e170 <_ZNSolsEPFRSoS_E>  
0x00401427 <_Z12outputStringPKc+57>:    leave  
0x00401428 <_Z12outputStringPKc+58>:    ret    
End of assembler dump.

All the disassemblies show only the manglinged function names,but its not eaiser for programmer to de-mangling and get the original function names with the bother to typing info symbol address for each mangling name met,so are there any methods that could make gdb show non-mangling function names on assembly model?

Auxiliaries

See also c++ - Function to mangle/demangle functions - Stack Overflow (it's possible to invoke shell from gdb) – Trigg

Answer 1

You could do maint demangle _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc at the (gdb) prompt.

The manual says:

`set print asm-demangle'
`set print asm-demangle on'
     Print C++ names in their source form rather than their mangled
     form, even in assembler code printouts such as instruction
     disassemblies.  The default is off.

Unfortunately, it doesn't appear to work:

(gdb) set print asm-demangle on
(gdb) disas
Dump of assembler code for function _Z12outputStringPKc:
0x00000000004009c4 <outputString(char const*)+0>:   push   %rbp
0x00000000004009c5 <outputString(char const*)+1>:   mov    %rsp,%rbp
0x00000000004009c8 <outputString(char const*)+4>:   sub    $0x10,%rsp
0x00000000004009cc <outputString(char const*)+8>:   mov    %rdi,-0x8(%rbp)
0x00000000004009d0 <outputString(char const*)+12>:  mov    $0x400bb0,%esi
0x00000000004009d5 <outputString(char const*)+17>:  mov    $0x6012a0,%edi
0x00000000004009da <outputString(char const*)+22>:  callq  0x400798 <_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@plt>
0x00000000004009df <outputString(char const*)+27>:  mov    %rax,%rdi
0x00000000004009e2 <outputString(char const*)+30>:  mov    -0x8(%rbp),%rsi
0x00000000004009e6 <outputString(char const*)+34>:  callq  0x400798 <_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@plt>
0x00000000004009eb <outputString(char const*)+39>:  mov    %rax,%rdi
0x00000000004009ee <outputString(char const*)+42>:  mov    $0x4007c8,%esi
0x00000000004009f3 <outputString(char const*)+47>:  callq  0x4007b8 <_ZNSolsEPFRSoS_E@plt>
0x00000000004009f8 <outputString(char const*)+52>:  leaveq 
0x00000000004009f9 <outputString(char const*)+53>:  retq   
End of assembler dump.

The setting changed how the current function is printed, but not how the functions it calls are printed (which is what I assume you are after).

I think that is a bug in GDB, please file a bug in bugzilla.

Update:

The bug has been fixed in 2013. With GDB-10.0 the output is:

(gdb) disas 0x555555555169
Dump of assembler code for function _Z12outputStringPKc:
   0x0000555555555169 <+0>:     push   %rbp
   0x000055555555516a <+1>:     mov    %rsp,%rbp
   0x000055555555516d <+4>:     sub    $0x10,%rsp
   0x0000555555555171 <+8>:     mov    %rdi,-0x8(%rbp)
   0x0000555555555175 <+12>:    lea    0xe8c(%rip),%rax        # 0x555555556008
   0x000055555555517c <+19>:    mov    %rax,%rsi
   0x000055555555517f <+22>:    lea    0x2efa(%rip),%rax        # 0x555555558080 <std::cout@GLIBCXX_3.4>
   0x0000555555555186 <+29>:    mov    %rax,%rdi
   0x0000555555555189 <+32>:    callq  0x555555555040 <std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)@plt>
   0x000055555555518e <+37>:    mov    %rax,%rdx
   0x0000555555555191 <+40>:    mov    -0x8(%rbp),%rax
   0x0000555555555195 <+44>:    mov    %rax,%rsi
   0x0000555555555198 <+47>:    mov    %rdx,%rdi
   0x000055555555519b <+50>:    callq  0x555555555040 <std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)@plt>
   0x00005555555551a0 <+55>:    mov    0x2e29(%rip),%rdx        # 0x555555557fd0
   0x00005555555551a7 <+62>:    mov    %rdx,%rsi
   0x00005555555551aa <+65>:    mov    %rax,%rdi
   0x00005555555551ad <+68>:    callq  0x555555555050 <std::ostream::operator<<(std::ostream& (*)(std::ostream&))@plt>
   0x00005555555551b2 <+73>:    nop
   0x00005555555551b3 <+74>:    leaveq
   0x00005555555551b4 <+75>:    retq

Predispose

There is a bug report, sourceware.org/bugzilla/show_bug.cgi?id=12021 . This only doesn't work for symbols with @plt suffix. – Harken

The problem I'm having is that the unmangled symbols are so long that they don't fit on 2 monitors... :) – Milne

In new version maint demangle is just demangle. – Trigg

The bug it also fixed now and set print asm-demangle on works just fine! – Taxi

Answer 2

I don't remember ever finding an automatic way for gdb to do it. I always just copied and pasted the symbol and ran it through the Linux c++filt utility to demangle.

Tanguay

are there any differences between c++filt and info symbol addr? – Auxiliaries

Answer 3

gdb show the original non-mangling function name on disassembly model ::

you have to do this steps every time whenever you are going to debug. 1. set print demangle on 2. set print asm-demangle on

Else you can create vim ~/.gdbinit file like ~/.vimrc file and set following steps so you no need to do every time on . 1 set print pretty on 2 set print demangle on 3 set print asm-demangle on

Southwestwards

Answer 4

To demangle an arbitrary symbol in newer version of GDB, type demangle xxx or shortly dem xxx.

For example:

(gdb) dem _ZN1C3fooEv
C::foo()
(gdb) dem _ZTV1C
vtable for C
(gdb) dem bar__C3Fooil
Foo::bar(int, long) const

ref: https://sourceware.org/gdb/current/onlinedocs/gdb.html/Debugging-C-Plus-Plus.html

Twopence