memset is causing infinite recursion with clang build

[X512]

This is hrev54001 x86_64 clang/lld build.

Clang produce memset call inside memset_small that is used by memset implementation causing infinite recursion (​https://git.haiku-os.org/haiku/tree/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp#n213).

This problem is causing crash in runtime_loader of init process and boot fail.

[waddlesplash]

Probably we need to compile arch_string with -disable-simplify-libcalls, or maybe even all of libroot with it.

[waddlesplash]

Actually, just putting it in string/Jamfile may be the right place. That way the rest of libroot can still take advantage of those optimizations.

[waddlesplash]

Eh, on second thought, it seems kind of dangerous to do those optimizations in the kernel or userland libraries at all; it's probably much better if we just add that flag across the board when compiling with Clang.

[pulkomandy]

Can't we just call __builtin_memset instead of having all this code, and let gcc/clang do the right thing?

[X512]

I tested __builtin_memset and it generate code that call regular memset.

[waddlesplash]

Uh, GCC/Clang __builtin_memset() only gets "inlined" for small copies (i.e. I think something like 64 bytes is the maximum), it is very primitive and not at all optimized for large (i.e. KBs/MBs) sets. We have to provide a memset one way or another.

[waddlesplash]

Fixed in hrev55661.