tags:

views:

4186

answers:

4

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?

+5  A: 

I think there isn't, at least not if your source is optimized etc. However, there are some macros for gdb that can inspect STL containers for you:

http://sourceware.org/ml/gdb/2008-02/msg00064.html

However, I don't use this, so YMMV

jpalecek
Thanks for the link; the only thing is that macros are dependent from the stl libraries version, which I'd prefer to avoid. +1
Paolo Tedesco
Its also a bit frustrating that commands like "plist foo std::string" give syntax errors. It appears that the value_type can't contain any punctuation.
Bklyn
I haven't tried, but if this works the same as the rest of GDB, enclosing the name with punctuated name in single quotes should do it.
jpalecek
+2  A: 

Try De-Referencing STL Containers: on this page: http://www.yolinux.com/TUTORIALS/GDB-Commands.html

anand
These look to be the business!
Richard Corden
They're actually the same macros as in the previous answer :) I'm afraid there's no simpler solution.
Paolo Tedesco
+1  A: 

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)
Mr.Ree
as long as the process is running. not so useful for core-dumps.
sean riley
+7  A: 

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