This code is attempting to be portable to C89, or why not just use C99's stdint.h? I don't believe your statement "C89 says the same thing," do you have a source to point to?
Do you have the section number in the latest freely available C99 working draft? The "Types" section (which 6.something in the draft) simply says what I said earlier about scalar rank. And 5.4.4.2.1 doesn't seem to exist in the draft.
Sorry, I mistyped the section number. Updated the parent comment with corrections and links.
I assume the intent of tweetnacl is to be C89-compatible, but due to the long long (and char, although that one's pretty pedantic) issue there's little guarantee of success.
Do you have the section number in the latest freely available C99 working draft? The "Types" section (which 6.something in the draft) simply says what I said earlier about scalar rank. And 5.4.4.2.1 doesn't seem to exist in the draft.