Question

I ran into a rather odd behavior that I don’t even know how to start describing.
I wrote a piece of managed C++ code that makes calls to native methods.

A (very) simplified version of the code would look like this (I know it looks like a full native function, just assume there is managed stuff being done all over the place):

int somefunction(ptrHolder x)
{
  // the accessptr method returns a native pointer
  if (x.accessptr() != nullptr) // I tried this with nullptr, NULL, 0)
  {
    try
    {
      x->doSomeNativeVeryImportantStuff(); // or whatever, doesn't matter
    }
    catch (SomeCustomExceptionClass &)
    {
      return 0;
    }
  }

  SomeOtherNativeClass::doStaticMagic();

  return 1;
}

I compiled this code without optimizations using the /clr flag (VS.NET 2005, SP2) and when running it in the debugger I get to the if statement, since the pointer is actually null, I don’t enter the if, but surprisingly, the cursor jumps directly to the return 1 statement, ignoring the doStaticMagic() method completely!!!

When looking at the assembly code, I see that it really jumps directly to that line.
If I force the debugger to enter the if block, I also jump to the return 1 statement after I press F10.

Any ideas why this is happening?

Thanks,
Ariel

Answer 1

Did you try checking that code is actually emitted for the SomeOtherNativeClass::doStaticMagic(); line? Perhaps the compiler couldn’t find it (or finds an empty function or something like that) and therefore skips it.

Second idea: Perhaps you are comparing two things which can’t be compared by using nullptr. So you get an exception, which is caught and causes you to exit the method directly.