[nlordell]

Both stb__addints_valid and stb__mul2shorts_valid are only used by the JPEG decoder and generate unused function warnings when not compiling with JPEG support:

// unused.c
#define STBI_NO_JPEG
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

$ cc -Wunused-function -c unused.c -o unused.o
In file included from unused.c:3:
./stb_image.h:1070:12: warning: unused function 'stbi__addints_valid' [-Wunused-function]
 1070 | static int stbi__addints_valid(int a, int b)
      |            ^~~~~~~~~~~~~~~~~~~
./stb_image.h:1078:12: warning: unused function 'stbi__mul2shorts_valid' [-Wunused-function]
 1078 | static int stbi__mul2shorts_valid(int a, int b)
      |            ^~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.

Just #if them out if not building with JPEG support. I used two separate #if blocks, one for each function, as that appeared to be the generally preferred pattern.

[nlordell]

Note that I did not add myself to the "Bug & warning fixes" contributor list, to avoid unnecessary merge conflicts. I generally don't mind being left out, especially for such a tiny contribution like this one.

[rygorous]

This is fixed in the dev branch, although other changes have since made this exact set of conditions incorrect - GIF now also depends on stbi__addints_valid. Closing this PR.