CODEWITHSUNDEEP
c++templatesgdbosx-mavericks
vsoftco
vsoftco

Reputation: 56577

GNU gdb can not step into template functions (OS X Mavericks)

I have installed gdb 7.7 (from GNU sources) under OS X Mavericks (10.9.2). I codesigned it, so it works fine whenever I debug a c++ file that does not contain templates. However, it is unable to step into template functions (can step into regular functions, but just fails to step into templated ones). When I type step command in a debugging session, it just steps over the function, as if the debugging symbols are not present for the template function. My template function is not even a member function, is just a simple function defined inside the main.cpp.

I compile my program with g++ -g -O0 main.cpp (I use g++4.8.2 from macports and not clang++), even tried -fno-inline, still same behaviour, cannot step into template functions. Is this a gdb known problem under OS X Mavericks? Or, can anyone reproduce the bug?

my code:

#include <iostream>

template <typename T> // template
void f(T x)
{
    std::cout << "In f:" << std::endl;
    std::cout << x << std::endl;
}

void g() // non-template
{
    std::cout << "It works here!" << std::endl;
    std::cout << "Exiting g()..." << std::endl;
}

int main() 
{
    f<double>(12.3); // gdb does not step into f()
    g(); // gdb steps into g()
}

Can not step in f after a breakpoint at f<double>(12.3). If f() is a regular function, such as g() in my code, then it steps into. Thanks!

Update: gdb works as it should under any other OS, such as linux/windows/solaris. It seems to be a problem related to OS X.

Reading symbols from a.out...done.
(gdb) disassemble main
Dump of assembler code for function main():
   0x0000000100000d62 <+0>: push   %rbp
   0x0000000100000d63 <+1>: mov    %rsp,%rbp
   0x0000000100000d66 <+4>: movabs $0x402899999999999a,%rax
   0x0000000100000d70 <+14>:    movq   %rax,%xmm0
   0x0000000100000d75 <+19>:    callq  0x100000e44
   0x0000000100000d7a <+24>:    callq  0x100000d0c <g()>
   0x0000000100000d7f <+29>:    mov    $0x0,%eax
   0x0000000100000d84 <+34>:    pop    %rbp
   0x0000000100000d85 <+35>:    retq
End of assembler dump.
(gdb)

Now we set a breakpoint at the entry of main() 

(gdb) b main
Breakpoint 1 at 0x100000d66: file src/templated_bug.cpp, line 22.
(gdb) r
Starting program: /Users/vlad/template_gdb_bug/a.out

Breakpoint 1, main () at src/templated_bug.cpp:22
22      f<double>(12.3);
(gdb) s
In f:
12.3
23      g();
(gdb) s
g () at src/templated_bug.cpp:16
16      cout<<"It works here!"<<endl;
(gdb) s
It works here!
17      cout<<"Exiting g()..."<<endl;
(gdb) s
Exiting g()...
18  }
(gdb) s
main () at src/templated_bug.cpp:24
24  }
(gdb) s
[Inferior 1 (process 50945) exited normally]
(gdb)

As you can see, it does not step inside f() but steps inside g(). Moreover,

(gdb) disassemble f
No symbol "f" in current context.

However, for another function g() that is non-template, the symbols are loaded and I can disassemble it.

(gdb) disassemble g
Dump of assembler code for function g():
   0x0000000100000d0c <+0>: push   %rbp
   0x0000000100000d0d <+1>: mov    %rsp,%rbp
   0x0000000100000d10 <+4>: lea    0x193(%rip),%rsi        # 0x100000eaa
   0x0000000100000d17 <+11>:    mov    0x2ea(%rip),%rax        # 0x100001008
   0x0000000100000d1e <+18>:    mov    %rax,%rdi
   0x0000000100000d21 <+21>:    callq  0x100000e5c
   0x0000000100000d26 <+26>:    mov    0x2e3(%rip),%rdx        # 0x100001010
   0x0000000100000d2d <+33>:    mov    %rdx,%rsi
   0x0000000100000d30 <+36>:    mov    %rax,%rdi
   0x0000000100000d33 <+39>:    callq  0x100000e4a
   0x0000000100000d38 <+44>:    lea    0x17a(%rip),%rsi        # 0x100000eb9
   0x0000000100000d3f <+51>:    mov    0x2c2(%rip),%rax        # 0x100001008
   0x0000000100000d46 <+58>:    mov    %rax,%rdi
   0x0000000100000d49 <+61>:    callq  0x100000e5c
   0x0000000100000d4e <+66>:    mov    0x2bb(%rip),%rdx        # 0x100001010
   0x0000000100000d55 <+73>:    mov    %rdx,%rsi
   0x0000000100000d58 <+76>:    mov    %rax,%rdi
   0x0000000100000d5b <+79>:    callq  0x100000e4a
   0x0000000100000d60 <+84>:    pop    %rbp
   0x0000000100000d61 <+85>:    retq
End of assembler dump.

Upvotes: 12

Views: 1884

Answers (1)

vershov
vershov

Reputation: 928

In seems there is an issues with the step into command at MacOS port of gdb. As workaround you could set breakpoint at the function start to step into the template function:

(gdb) b f<double>
Breakpoint 1 at 0x1000015ab: file ./gdb_tmpl.cpp, line 6.
(gdb) run
Starting program: /Users/vershov/tmp/tests/a.out 

Breakpoint 1, f<double> (x=12.300000000000001) at ./gdb_tmpl.cpp:6
6       std::cout << "In f:" << std::endl;

Also, you could disassemble it, just use correct command:

(gdb) disass f
No symbol "f" in current context.
(gdb) disass f<double>
Dump of assembler code for function f<double>(double):
   0x0000000100001590 <+0>: push   %rbp
   0x0000000100001591 <+1>: mov    %rsp,%rbp
   0x0000000100001594 <+4>: sub    $0x40,%rsp
   0x0000000100001598 <+8>: mov    0xa71(%rip),%rdi        # 0x100002010
   0x000000010000159f <+15>:    lea    0x9a0(%rip),%rsi        # 0x100001f46
...

Upvotes: 3

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