No, actually, I did see this. The problem with using STBI_MALLOC in that way is that it is used for _all_ allocations by STB, not just the main image buffer. The image buffer I need to put the data into is passed in as an argument to Gfx Tools. It is already existing, and I couldn't touch the code where it was created, that code lived in yet another DLL, the one calling into Gfx Tools. So if I overrode STBI_MALLOC to just return that same buffer every time, then any time STB calls malloc, each malloc call would return the same buffer, that same buffer would be used for different allocations with entirely different purposes. So, it's close, but it wouldn't work. I would need to have done some hack like checking the requested buffer size to malloc matches the expected size of the image buffer, and only return it then, but that's of course quite fragile and error prone. Or, you know, just go into the STB source and find the one malloc I need to replace, but that's kind of dirty.