cgo: implement support for static functions

[aykevl]

This depends on #2774.

Static functions are used in tinygo.org/x/bluetooth but so far we've mostly just worked around them. This implements proper support for static functions.

[aykevl]

Error: /Users/runner/work/tinygo/tinygo/testdata/cgo/extra.go:9:78: error: aliases are not supported on darwin
void _Cgo_static_8fa7a76b0410251fc60e_headerfunc_static(void) __attribute__((alias("headerfunc_static")));

grumble

[aykevl]

I expected this to be necessary for tinygo-org/drivers#401 but apparently it's not.

[deadprogram]

Now that #2774 has been merged, this PR should now be able to be moved forward.

[aykevl]

Unfortunately, not. It doesn't work on MacOS yet. I need to work around that somehow.

[ysoldak]

Unfortunately, not. It doesn't work on MacOS yet. I need to work around that somehow.

I've found this workaround for MacOS, can we use it?
https://github.com/besser82/libxcrypt/blob/b8c6d0475f5e1a87a6dfbc9f62b7402b69052049/lib/crypt-port.h#L191-L198

/* Darwin (Mach-O) doesn't support alias attributes or symbol versioning.
   It does, however, support symbol aliasing at the object file level.  */
#ifdef __APPLE__

# define _strong_alias(name, aliasname)         \
  __asm__(".globl _" #aliasname);               \
  __asm__(".set _" #aliasname ", _" #name);     \
  extern __typeof(name) aliasname __THROW

[aykevl]

@ysoldak thanks for this suggestion! I was aware of the linker feature but didn't know how to use it from C.

Unfortunately, the linker we use doesn't support aliases:

ld.lld-14: error: TODO: support symbols of type 10
ld.lld-14: error: TODO: support symbols of type 10
ld.lld-14: error: undefined symbol: __Cgo_static_425e352dd21e64a2b260_headerfunc_static
>>> referenced by /tmp/tinygo2273409226/main.o

ld.lld-14: error: undefined symbol: __Cgo_static_f2b9c44701219e7a3dfe_headerfunc_static
>>> referenced by /tmp/tinygo2273409226/main.o
error: failed to link /tmp/tinygo2273409226/main: exit status 1

Perhaps I can try to add support...

[ysoldak]

"the linker we use doesn't support aliases", you mean this?

ld.lld-14: error: TODO: support symbols of type 10

[aykevl]

Yes. "symbol of type 10" refers to aliases.

[aykevl]

I've added a workaround for MacOS, let's see whether it works.

[ysoldak]

It works on my Mac at least. macOS 12.5.1
I've tried

GOOS=darwin GOARCH=amd64 tinygo  build  -size short -o test       ./testdata/cgo
   code    data     bss |   flash     ram
  12734     112     145 |   12846     257

and

GOOS=darwin GOARCH=arm64 tinygo  build  -size short -o test       ./testdata/cgo
   code    data     bss |   flash     ram
  12704     120     136 |   12824     256

[aykevl]

Reminder: this PR is ready for review.

[deadprogram]

😿 oh Apple

[aykevl]

The worst part is that the linker actually does support aliases, it's just the compiler that doesn't.
...and I don't feel like creating a Clang patch and pushing for its inclusion.

[deadprogram]

I am really looking forward to being able to compile some libs that have not been easily importable until now.

[deadprogram]

Merging!!