efriedma-quic wrote: -ffreestanding currently has the following effects: - Disables builtins recognition (-fno-builtins) - Sets `__STDC_HOSTED__` to 0. - Disables unwind tables (-fno-asynchronous-unwind-tables -fno-unwind-tables) (refer to df50259f9856ae98b5a1b34c4c955074aff3c566)
Maybe we should explicitly list this out in the documentation. We might want to check existing uses of `__STDC_HOSTED__` to see if we need to modify the interaction if we have a libc. A few of the headers in clang/lib/Headers/ make assumptions about the presence of libc based on `__STDC_HOSTED__`. At first glance, we're probably fine, but we might want to come up with some sort of policy. As a practical matter, nobody really cares what the C committee has to say about freestanding implementations; everyone makes different tradeoffs depending on the constraints of their environment. Some "baremetal" environments have an extremely complete C library including I/O, and the usual "main" function. Some have absolutely nothing (even less than what we say clang requires). And everything in between. I don't think we need to say anything about how startup works in a freestanding environment; I think we just refer people to their environment's documentation. We say "memcpy, memmove, memset, memcmp" because that's what the corresponding gcc documentation says, but I don't think clang has ever generated calls to memcmp in -fno-builtins mode. https://github.com/llvm/llvm-project/pull/132232 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
