Question

I have this weird bug, where C++ calls the wrong function:

So this bit of code get called:

  class FmeGrid
  {  
     // ....
     virtual void saveGridParameters() const;
     virtual void setCellSignalValue(int row, int col, double double_value, const std::string& string_value);
     // ....
  }

  void EnfClientFrame::saveGridParameters()
  {
    this->grid->saveGridParameters();
  }

And the next function in the stack that is called is:

  void FmeGrid::setCellSignalValue(int row, int col, double double_value, const std::string& string_value)
  {
    this->setCellString(row, col, string_value, wxALIGN_RIGHT);
    this->setCellBackground(row, col, GetSignalColour(double_value));
  }

With totally random values, here is the stack:

enf_client.exe!ui::FmeGrid::setCellSignalValue(int row=1239452, int col=1239236, double double_value=-9.2559592117431994e+061, const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & string_value={...})  Line 468 + 0x23 bytes  C++
enf_client.exe!ui::EnfClientFrame::saveGridParameters()  Line 170 + 0x20 bytes  C++

So the “grid” pointer points to a class that inherits from FmeGrid (and only from FmeGrid).
saveGridParameters is a virtual function, so it may be because of that.

Answer 1

Most common causes for this are:

1. Dirty build (i.e. interface changed, but objects that used those interfaces weren’t rebuilt)
2. Stack corruption (you overwrote something on the stack that’s causing the wrong function to be called and/or the correct function with invalid arguments)

Try fixing with a clean rebuild and if it still happens, then try a memory debugging tool (like Valgrind) to see where you’re overwriting the stack.