Builds for embedded powerpcle64 have no unmangled memset/memcpy/memmove

[tomtor]

See antonblanchard/microwatt#125

I have to define my own memset/memcpy/memmove in the calling C-program:

https://github.com/tomtor/microwatt/blob/37bc1f31c2139ec06a56e51ed595e0bc664fdbc8/rust_lib_demo/hello_world.c#L172

This looks related to #56814

[jonas-schievink]

We don't have any embedded (#![no_std]) PowerPC targets. You are building for powerpc64le-unknown-linux-gnu, which assumes that libc provides these functions.

[tomtor]

Adding /usr/powerpc64le-linux-gnu/lib/libc.a

gives

/usr/powerpc64le-linux-gnu/lib/libc.a(fileops.o): In function `_IO_new_file_underflow':
(.text+0x628): undefined reference to `_Unwind_Resume'
/usr/powerpc64le-linux-gnu/lib/libc.a(printf_fp.o): In function `__printf_fp_l':
(.text+0x650): undefined reference to `__unordkf2'
(.text+0x68c): undefined reference to `__unordkf2'
(.text+0xcf8): undefined reference to `__lekf2'
/usr/powerpc64le-linux-gnu/lib/libc.a(printf_fphex.o): In function `__printf_fphex':
(.text+0xf8): undefined reference to `__unordkf2'
(.text+0x144): undefined reference to `__unordkf2'
(.text+0x164): undefined reference to `__lekf2'
/usr/powerpc64le-linux-gnu/lib/libc.a(iofputs.o): In function `_IO_fputs':
(.text+0x204): undefined reference to `_Unwind_Resume'
/usr/powerpc64le-linux-gnu/lib/libc.a(iofwrite.o): In function `_IO_fwrite':
(.text+0x2f4): undefined reference to `_Unwind_Resume'
/usr/powerpc64le-linux-gnu/lib/libc.a(iogetdelim.o): In function `_IO_getdelim':
(.text+0x460): undefined reference to `_Unwind_Resume'
Makefile:34: recipe for target 'hello_world.elf' failed

So for some reason not just memcpy is copied in.

I see in #56814 that unmangled versions USED to be in the compiler_builtins but were remove because they are not needed for ARM targets?

[tomtor]

We don't have any embedded (#![no_std]) PowerPC targets.

@jonas-schievink Indeed an official tier-2 embedded PowerPC target would be nice, but I would expect that a specific xargo configuration (I already use xargo for building a working soft-float library) would allow use of the current powerpc64le-unknown-linux-gnu target.

I fixed it now with this Xargo.toml:

[target.powerpc64le-unknown-linux-gnu.dependencies]

[dependencies.alloc]
features = ["compiler-builtins-mem"]