You're right.

Their expression (simplified) was: *target = pixels[j] << 24, where pixels contains items of type unsigned char.

I hadn't realized that the pixels[j] was being promoted to an int rather than unsigned int. Eeep.

> I really dislike the promotion logic in C.

Agreed. I'll add that to my list of C dislikes.

I still think that even with manually promoting to the appropriate unsigned type isn't sufficient. Because target has type long*, so coercing the result of (unsigned int)pixels[j] << 24 to long still causes overflow and therefore UB... unless there's yet more I've missed.

Edit: Damn it, again, that's what the discussion says (https://github.com/glfw/glfw/pull/1986#issuecomment-95800024...).