printf("%zd") of ssize_t variables results in a warning

[heatd]

It is possible that the ssize_t definition is just slightly wrong for some targets.

From IRC: https://gist.github.com/heatd/844f6bb11370b66468669098bb918a4d

Example warnings: https://gist.github.com/heatd/3a0ba9c7710706d6298572018ef573a1

[travisg]

Fixed on master as of 8c61f616.

You were right that the ssize_t definition was "just slightly wrong for some targets". It was hardcoded to signed long int, while size_t comes from the compiler — so on any ILP32 target where __SIZE_TYPE__ is unsigned int (arm, riscv32, or1k, microblaze) the two were not a signed/unsigned pair and %zd tripped -Werror=format=. The house workaround had been to write %ld instead, which is then wrong on i386 and m68k, where __SIZE_TYPE__ is long unsigned int. No hardcoded type is right everywhere.

It's now typedef __PTRDIFF_TYPE__ ssize_t;, which is exactly the signed counterpart of __SIZE_TYPE__ on every target LK builds for — verified against the arm, aarch64, riscv32, riscv64, i386, x86_64, m68k, microblaze and or1k gcc toolchains and against clang. %zd is now correct everywhere, and the %ld sites that were working around it have been swept.

The fix came in via PR #412, which was doing the same thing for a different reason.