Missing symbols on aarch64-unknown-linux-musl

[Amanieu]

When compiling a simple hello world crate for aarch64-unknown-linux-musl, I get the following error:

          /home/amanieu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/aarch64-unknown-linux-musl/lib/liblibc-3c62182e850a1e7a.rlib(vfprintf.o): In function `fmt_fp':
          vfprintf.c:(.text.fmt_fp+0x178): undefined reference to `__addtf3'
          vfprintf.c:(.text.fmt_fp+0x20c): undefined reference to `__multf3'
          vfprintf.c:(.text.fmt_fp+0x240): undefined reference to `__subtf3'
          vfprintf.c:(.text.fmt_fp+0x250): undefined reference to `__addtf3'
          vfprintf.c:(.text.fmt_fp+0x278): undefined reference to `__addtf3'
          vfprintf.c:(.text.fmt_fp+0x284): undefined reference to `__subtf3'
          vfprintf.c:(.text.fmt_fp+0x33c): undefined reference to `__subtf3'
          vfprintf.c:(.text.fmt_fp+0x344): undefined reference to `__multf3'
          vfprintf.c:(.text.fmt_fp+0x4e8): undefined reference to `__multf3'
          vfprintf.c:(.text.fmt_fp+0x548): undefined reference to `__subtf3'
          vfprintf.c:(.text.fmt_fp+0x550): undefined reference to `__multf3'
          vfprintf.c:(.text.fmt_fp+0x828): undefined reference to `__addtf3'
          /home/amanieu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/aarch64-unknown-linux-musl/lib/liblibc-3c62182e850a1e7a.rlib(frexpl.o): In function `frexpl':
          frexpl.c:(.text.frexpl+0x38): undefined reference to `__multf3'
          collect2: error: ld returned 1 exit status

It would seem that the __addtf3, __subtf3 and __multf3 symbols are used by musl but are not provided by compiler-builtins.

[asonix]

Alright, it seems based on this link that __addtf3, and the other tf3 functions are expecting long double or a 'triple float'. On aarch64, this occupies 128 bits (as demonstrated by my really basic C program I just compiled on a pine64)

asonix@pine64:~$ cat test.c 
#include <stdio.h>

int main() {
	float x = 2.0;
	double y = 2.0;
	long double z = 2.0;

	printf("float: %lu\n", sizeof(x));
	printf("double: %lu\n", sizeof(y));
	printf("long double: %lu\n", sizeof(z));
	return 0;
}
asonix@pine64:~$ gcc test.c -o test.bin
asonix@pine64:~$ ./test.bin 
float: 4
double: 8
long double: 16
asonix@pine64:~$ 

Whether this means that long doubles occupy the whole 128 bits, or just part of them I am unsure, but my guess would be to implement these with f128s

Edit:
Well, since f128s don't exist anymore I guess this is blocked

[Amanieu]

Fixed by rust-lang/libc#1034.

[Amanieu]

Reopening due to rust-lang/libc#1045

[bbqsrc]

This bit me recently, and the workaround here is a temporary but functional fix, though it does leave a dry taste in the mouth.

[ciofeca]

Fresh install of Rust 1.30 on x86_64, tried to compile, errors still there. Sigh!

[parched]

@Amanieu can we fix this by applying your libc patch again and making all symbols in this crate weak symbols?

[Amanieu]

I think we can link libgcc as static-nobundle which should avoid the link error.