Inspecting standard container (std::map) contents with gdb

orsogufo_15622 0
Viewed 107828

Supposing to have something like this:

#include <map>
int main(){
    std::map<int,int> m;
    m[1] = 2;
    m[2] = 4;
    return 0;
}

I would like to be able to inspect the contents of the map running the program from gdb.
If I try using the subscript operator I get: 

(gdb) p m[1]
Attempt to take address of value not located in memory.

Using the find method does not yield better results:

(gdb) p m.find(1)
Cannot evaluate function -- may be inlined

Is there a way to accomplish this?

gdb map stl c++
7 Answers
user_518310

There's always the obvious: Define your own test-function... Call it from gdb. E.g.:

#define SHOW(X) cout << # X " = " << (X) << endl

void testPrint( map<int,int> & m, int i )
{
  SHOW( m[i] );
  SHOW( m.find(i)->first );
}

int
main()
{
    std::map<int,int> m;
    m[1] = 2;
    m[2] = 4;
    return 0;  // Line 15.
}

And:

....
Breakpoint 1 at 0x400e08: file foo.C, line 15.
(gdb) run
Starting program: /tmp/z/qD 

Breakpoint 1, main () at qD.C:15
(gdb) call testPrint( m, 2)
m[i] = 4
(*m.find(i)).first = 2
(gdb)
user_379460

The stl-views.gdb used to be the best answer there was, but not anymore.

This isn't integrated into the mainline GDB yet, but here is what you get using the 'archer-tromey-python' branch:

(gdb) list
1   #include <map>
2   int main(){
3       std::map<int,int> m;
4       m[1] = 2;
5       m[2] = 4;
6       return 0;
7   }
(gdb) break 6
Breakpoint 1 at 0x8048274: file map.cc, line 6.
(gdb) run

Breakpoint 1, main () at map.cc:6
6       return 0;
(gdb) print m
$1 = std::map with 2 elements = {
  [1] = 2,
  [2] = 4
}
(gdb) quit
Employed_Russian_506170
anand_525540

The answers above are working and fine. In case you are using stl-views.gdb, here is the proper way of viewing the maps and elements inside it. Let your map is as follows : std::map<char, int> myMap;

(gdb) pmap myMap char int

i.e. pmap <variable_name> <left_element_type> <right_element_type> to see the elements in the map.

Hope that helps.

user_68416760
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