Can companion declarations be avoided for private functions?

[starius]

I'm trying to convert a big library which has many functions calling each other and just few of them are public. Nevertheless I have to write a lot of declarations in the companion file for all those private assembly functions, which is boring. Are they really needed for private functions?

[fwessels]

If you don't need them from Golang you should be able to leave them out. And maybe really make sure that they are private, or even inlined by the compiler.

[starius]

I marked functions static and c2goasm just skipped them.

Note that I applied my fix from https://github.com/minio/c2goasm/issues/15 to fix the crash.

$ cat f.c
static int foo(int (*f)(int), int arg) {
    return f(arg) + 1;
}

static int bar(int x) {
    return x * 2;
}

int buz() {
    return foo(bar, 5);
}

$ clang-6.0 -O0 -mavx -mfma -masm=intel -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -S f.c -o f.s                                                                           

$ cat f.s
        .text
        .intel_syntax noprefix
        .file   "f.c"
        .globl  buz                     # -- Begin function buz
        .p2align        4, 0x90
        .type   buz,@function
buz:                                    # @buz
# %bb.0:
        push    rbp
        mov     rbp, rsp
        movabs  rdi, offset bar
        mov     esi, 5
        call    foo
        pop     rbp
        ret
.Lfunc_end0:
        .size   buz, .Lfunc_end0-buz
                                        # -- End function
        .p2align        4, 0x90         # -- Begin function foo
        .type   foo,@function
foo:                                    # @foo
# %bb.0:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 32
        mov     qword ptr [rbp - 8], rdi
        mov     dword ptr [rbp - 12], esi
        mov     rdi, qword ptr [rbp - 8]
        mov     esi, dword ptr [rbp - 12]
        mov     qword ptr [rbp - 24], rdi # 8-byte Spill
        mov     edi, esi
        mov     rax, qword ptr [rbp - 24] # 8-byte Reload
        call    rax
        add     eax, 1
        add     rsp, 32
        pop     rbp
        ret
.Lfunc_end1:
        .size   foo, .Lfunc_end1-foo
                                        # -- End function
        .p2align        4, 0x90         # -- Begin function bar
        .type   bar,@function
bar:                                    # @bar
# %bb.0:
        push    rbp
        mov     rbp, rsp
        mov     dword ptr [rbp - 4], edi
        mov     edi, dword ptr [rbp - 4]
        shl     edi, 1
        mov     eax, edi
        pop     rbp
        ret
.Lfunc_end2:
        .size   bar, .Lfunc_end2-bar
                                        # -- End function

        .ident  "clang version 6.0.0-1~bpo9+1 (tags/RELEASE_600/final)"
        .section        ".note.GNU-stack","",@progbits

$ c2goasm -a f.s gofunc/f_amd64.s
Processing f.s
Invoking asm2plan9s on gofunc/f_amd64.s

$ cat ./gofunc/f_amd64.s
//+build !noasm !appengine
// AUTO-GENERATED BY C2GOASM -- DO NOT EDIT

TEXT ·_buz(SB), $0-8

    LONG $0x00c7c748; WORD $0x0000; BYTE $0x00 // mov    rdi, offset bar
    LONG $0x000005be; BYTE $0x00 // mov    esi, 5
        CALL foo
    MOVQ AX, result+0(FP)
    RET

$ go get ./gofunc/
# func-call/gofunc
gofunc/f_amd64.s:12: undefined label foo
asm: invalid instruction: 00039 (gofunc/f_amd64.s:9)   CALL
asm: assembly failed

[lrita]

The ABI of go asm is different with C. I think the tool is missing concern this.