The changes you introduced around the integer constant macros look good overall and follow the expected pattern for defining INTxx_C and UINTxx_C. I appreciate the effort to make the definitions conditional on INTSIZE, which ensures portability across different platforms. One thing to note is consistency: the suffix usage (L for signed, U for unsigned) is correct, but in the UINT16_C branch you directly append U without considering L for longer integer cases, which might cause issues on compilers where int is smaller than 16 bits. It would be worth double-checking whether appending UL is safer in environments where unsigned int is not guaranteed to hold 16 bits. Additionally, the formatting looks a little uneven, so aligning indentation across all the macro definitions would improve readability. Overall, this is a solid improvement for type safety and cross-platform compatibility, but I recommend a quick pass for suffix consistency and style polish before merging.