namespace and argument dependent name lookup (ADL) in gdb

namespace and argument dependent name lookup (ADL) in gdb

[Peng Yu]

Hi,

I don't have to write test::f in the following program because of
argument dependent name lookup.

http://en.wikipedia.org/wiki/Argument_dependent_name_lookup

But to debug such program, I have to write the namespace test. For example,
(gdb) tb f
Function "f" not defined.
(gdb) tb test::f
Breakpoint 1 at 0x804867c: file main.cc, line 11.

I'm wondering if gdb supports ADL. In a big program, it might not be
easy for me to find out which namespace is the function "f" in. If gdb
support ADL, it would save user a lot of time.

Thanks,
Peng

#include <iostream>

namespace test {

  struct A {
    A() : x(10) { }
    int x;
  };

  void f(const A &a) {
    std::cout << a.x << std::endl;
  }

}

int main(){
  test::A a;
  f(a);//do not have to write test::f
}

Re: namespace and argument dependent name lookup (ADL) in gdb

[Daniel Jacobowitz]

On Wed, Dec 12, 2007 at 09:38:53PM -0600, Peng Yu wrote:
> Hi,
> 
> I don't have to write test::f in the following program because of
> argument dependent name lookup.
> 
> http://en.wikipedia.org/wiki/Argument_dependent_name_lookup
> 
> But to debug such program, I have to write the namespace test. For example,
> (gdb) tb f
> Function "f" not defined.
> (gdb) tb test::f
> Breakpoint 1 at 0x804867c: file main.cc, line 11.

That's not Koenig lookup.  There's no arguments.  If you were already
in the namespace 'test', GDB would search it.

> I'm wondering if gdb supports ADL. In a big program, it might not be
> easy for me to find out which namespace is the function "f" in. If gdb
> support ADL, it would save user a lot of time.

GDB supports some kinds of context-sensitive lookup, but not this one.
It is too complex to reconstruct the necessary information in the
debugger to do accurate name lookup.


-- 
Daniel Jacobowitz
CodeSourcery

Re: namespace and argument dependent name lookup (ADL) in gdb

[Daniel Jacobowitz]

On Fri, Dec 14, 2007 at 05:15:06PM -0600, Peng Yu wrote:
> > > (gdb) tb test::f
> > > Breakpoint 1 at 0x804867c: file main.cc, line 11.
> >
> > That's not Koenig lookup.  There's no arguments.
> 
> Why there is no argument? a is f's argument.

You typed "tb f".  There's no a in that.  GDB only works from
what you type.

> >  If you were already
> > in the namespace 'test', GDB would search it.
> 
> What if I'm in the function body of "main"?

Then type "tb test::f".  You have to know where things are defined by
looking through the source.  You can also use "info function" to search.

-- 
Daniel Jacobowitz
CodeSourcery