Re: GCC vs MSVC compiler issues in a port

[Andrew Haley <aph at redhat dot com>]

On 12/22/2012 09:07 AM, John Cotton Ericson wrote:
> Hello,
> 
> For a little over a year I have worked on porting the a voxel engine 
> called Voxlap to work on Linux. My code is here: 
> https://github.com/Ericson2314/Voxlap
> 
> I now can compile the same code with both MSVC and gcc. The MSVC code 
> runs well enough, but the gcc version does not. Specifically when I run 
> the MSVC version, everything in-game renders, and a bit of text is 
> thrown on top as a watermark. When I run  the gcc version, all I get is 
> a black window and that water mark. The problem is exactly whether I 
> compile on windows with mingw or compile on linux. In both cases I am 
> compiling the same branch with most of the inline assembly converted to 
> C, and in both cases I compile against the SDL backend, not the direct X 
> backend.
> 
> Because I have done my best to hold everything else constant, I am 
> pretty convinced this error is either due to some subtle difference's in 
> the two compile's understanding of the C semantics, or an error in the 
> gcc version of what inline assembly remains (inline assembly being the 
> only code I can think of which is #ifdefed based on the compiler).
> 
> After a couple of months of sporadically trying to solve this issue, I 
> am at a loss what to do next. As I did not write the original renderer, 
> and thus I am only so familiar with it's inner workings. I was hoping 
> somebody more experience with porting or more knowledge of subtle 
> differences between gcc and MSVC would be able to help me solve this 
> issue, which should be the last before I have a basic gcc version ready.

You need to start with an unoptimized build; does it crash in the
same way?  What about building with -Wall ?

Andrew.