Gdb will not perform binary operation

Question

I have the following code

#include <iostream>

using namespace std;

class Point2D
{
public:

  double x;
  double y;

  Point2D(double x_i,
      double y_i):
    x(x_i), y(y_i) {}
};

Point2D operator+(const Point2D& p1,
          const Point2D& p2)
{
  return Point2D(p1.x+p2.x, p1.y+p2.y);
}

Point2D operator*(double s, const Point2D& p)
{
  return Point2D(p.x*s,p.y*s);
}

ostream& operator<<(ostream& os, const Point2D& p)
{
  os << p.x << " " << p.y << endl;
  return os;
}

int main(void)
{
  const Point2D p1(2,3);
  const Point2D p2(5,4);

  cout << 0.5*(p1+p2) << endl;

  return 0;
}

I can compile it and get the correct result, but I have problems when I try to debug it. Obviously, the compiler can figure out how to perform a binary operation, but the debugger cannot. My compiler version is g ++ (Ubuntu 4.9.1-16ubuntu6) 4.9.1.

$ g++ -g ./for_stack_overflow.cpp && gdb ./a.out 
GNU gdb (Ubuntu 7.8-1ubuntu4) 7.8.0.20141001-cvs
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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and "show warranty" for details.
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Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
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Reading symbols from ./a.out...done.
(gdb) break 41
Breakpoint 1 at 0x400b90: file ./for_stack_overflow.cpp, line 41.
(gdb) r
Starting program: /home/almog/Documents/a.out 
3.5 3.5


Breakpoint 1, main () at ./for_stack_overflow.cpp:41
41    return 0;
(gdb) print 0.5*(p1+p2)
Can't do that binary op on that type
(gdb) 

Am I doing something wrong or is there a problem with the debugger?

Answer 1

p1 + p2 is equivalent to calling the overloaded operator + method, but this operator to the method constraint is executed at compiled time. therefore gdb does not know which method to call.