I’m compiling a c++ dll from a reasonably well vetted library (zeromq), and consuming it in my own Delphi bindings. I’m currently hitting an unexpected behavior in the C++ code, and don’t have the background to debug it well. The ultimate responsibility for the bug is probably in my Delphi code, but I need to understand the C++ better to know what I did wrong.

The problem code looks like this (simplified)

 if (*mySize_tObject == sizeof (uint64_t)) {
     return 0;//We never reach this code.
 }

*mySize_tObject is passed in as a size_t. In my Delphi bindings, it is a Cardinal with a value of 8.

I’ve tried playing around with the C++ outputs to narrow down what might be happening, and gotten these results:

return *mySize_tObject;//8
return sizeof (uint64_t);//8
return *mySize_tObject + sizeof (uint64_t);//16
if(*mySize_tObject > sizeof (uint64_t)) return 1;//1 
if(*mySize_tObject < sizeof (uint64_t)) return 1;//not 1 

So I’m getting back, essentially, 8>8. Since I know that isn’t true (citation needed), I’m left thinking that one of these values is secretly a float like 8.000001 and I’m only seeing truncated results.

I would also consider tips for live debugging a .dll if this doesn’t make any sense to people that know c++.