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Freestanding OCaml runtime
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How to add support for <inttypes.h> #60

Closed emillon closed 4 years ago

emillon commented 5 years ago

Hello,

I'm trying to build a library that uses <inttypes.h>, more specifically it's in hacl - the PRIu64 macro is used - it should expand to a format string specifier. This C99 header are unfortunately not supported in ocaml-freestanding.

In this particular case I might be able to patch my way around this problem (this debug code can be stripped), but this is not ideal as this code is extracted, so I'd rather not touch it too much.

How would I go about adding support for <inttypes.h>? can I just add inttypes.h in nolibc/include/?

(same would apply to bswap64 - I recall adding it to a couple libraries because it was missing in freestanding)

Thanks!

dinosaure commented 5 years ago

Where it's mostly used to print something in the C side, I'm not very convince to add inttypes.h just for that. A better idea (according the fact that this file is generated), IHMO, should be to fake PRIu64 with something else by the -D option or another header C file. ocaml-freestanding should be smallest as we can.

mato commented 5 years ago

@emillon:

musl inttypes.h depends on a fair bit of libc "infrastructure", however all we would support from it are the printf format string macros. So, as a minimum, you'd need to replace the #if UINTPTR_MAX == UINT64_MAX block with some #if logic that compiles correctly on the architectures we support.

As @dinosaure says, in general we want to keep ocaml-freestanding as small as possible, so it may be better to disable the offending code (given that it's just for debug), or patch the source to add some #defines.