• entries
455
639
• views
421685

# Debugging and compiler errors

79 views

It's not very often I get to say this, but I think I've found a compiler bug in VC8.0 SP1; Well, maybe not a 'bug' but certainly something I didn't expect...

int createTexture(GTL::ImagePtr tex){	const bool texurePowerOfTwo = isImagePowerTwo(tex);	const bool hasGL2 = GLEE_VERSION_2_0;	const bool hasNPOT = GLEE_ARB_texture_non_power_of_two; 	if(!texurePowerOfTwo && (!hasGL2 && !hasNPOT))		return 0;	// NPOT textures supported on GL2.0 and later as well as hardware which shows the extension 	GLuint texture;	glGenTextures(1,&texture);	glBindTexture(GL_TEXTURE_2D,texture); 	// the following statesments are here to show how the rest of the code looks	if (a)	{		// do stuff with no return statement	}	else if(b)	{		// do other stuff with no return statement	}	else if(c)	{		// do other other stuff with no return statement	}}

Now, the function this comes from is long, thus the short version above, however there is one fundimental error; under normal operation it doesn't work right.

Near the top we have the check to see if we can handle certain combinations of texture data and GL extensions/caps, if we can't we return 0. If we can however the rest of the code is then run and the function just drops out of the bottom with the final return value being whatever happens to be in the return register.

Now, I expected the compiler to catch this, however it seems that, for some reason, it doesn't o.O

I also had to perform some code changes as apprently lua_objlen doesn't return the number of elements in a table if they aren't indexed. This was mucking up a few functions which relied on that count to work out how many parameters were called.

The 'get*FromTable' functions also needed a rejiggle as I forgot to pop any resulting 'nil' values from the stack when returning the default value. I need to change this however as the default value being returns is, in some cases, a legal value.

For the bool accesses it makes sense to return 'false' is something isn't present, however for the number accesses 0 could be a valid number. I don't want to use exceptions because a value not being there isn't an exceptional situation, for example when it comes to colour data it's perfectly reasonable to send only RGB data, so trying to read the alpha value would fail, but at the same time the default value of '0' is a valid alpha value.

I guess I could do a 'query' and then 'obtain' function pair, however I'm not overly happy with this solution.

I've got to do a time trial to my possible place of work, so I'll consider it while dodging traffic... [grin]

## 1 Comment

Quote:
 I've got to do a time trial to my possible place of work
I've not been keeping up with journals as much as I'd like, but I remember you writing about jobs a while back. You've got somewhere with it I take it?

Jack