bytealg.CountString is not supported

[1l0]

main.go:

package main

import (
	"fmt"
	"strings"
)

func main() {
	s := strings.Replace("abc", "a", "x", -1)
	fmt.Println(s)
}

run:

$ tinygo run main.go
Undefined symbols for architecture x86_64:
  "_internal/bytealg.CountString", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: failed to link /var/folders/kt/gfbj96zj1jvd9tsbbfjcg94h0000gn/T/tinygo175846444/main: exit status 1
$ go run main.go
xbc

How can I fix this?

[aykevl]

A related function is implemented here in the runtime, which you can use as an example:

tinygo/src/runtime/string.go

Lines 184 to 194 in 40b193f

	// indexByteString returns the index of the first instance of c in s, or -1 if c
	// is not present in s.
	//go:linkname indexByteString internal/bytealg.IndexByteString
	func indexByteString(s string, c byte) int {
	for i := 0; i < len(s); i++ {
	if s[i] == c {
	return i
	}
	}
	return -1
	}

You could either implement your own version, or copy the one from the Go standard library:
https://github.com/golang/go/blob/master/src/internal/bytealg/count_generic.go
But note that if you copy from the standard library, you have to clearly state where it came from.

[1l0]

I wonder if I have understood correctly.
Should following be compiled by TinyGo (actually failed) or do I have to compile TinyGo itself with a modification?

package main

import (
	"fmt"
	"strings"
	_ "unsafe"
)

func main() {
	s := strings.Replace("abc", "a", "x", -1)
	fmt.Println(s)
}

// paste from https://github.com/golang/go/blob/67f181bfd84dfd5942fe9a29d8a20c9ce5eb2fea/src/internal/bytealg/count_generic.go#L19
//go:linkname countString internal/bytealg.CountString
func countString(s string, c byte) int {
	n := 0
	for i := 0; i < len(s); i++ {
		if s[i] == c {
			n++
		}
	}
	return n
}

[aykevl]

Sorry for the late reply.

Outside of the runtime, //go:linkname doesn't always work. This is a bug I'm aware of and should be fixed in the not too distant future hopefully (see #285). So simply moving this function to the runtime should get it to compile.

[1l0]

OK I will wait the party.

[deadprogram]

I think what @aykevl was saying @1l0 was that if you add that code to the correct place in the runtime will let it compile. You can then submit a PR and this should be solved.

The //go:linkname directive does not work on code outside of the runtime but works fine when used within the runtime.

Thanks!

[aykevl]

Exactly, what @deadprogram says. There is no reason to wait, just move countString into the runtime to get it to compile (where it belongs anyway).

[1l0]

Do you prefer that route (I mean patchwork-like)? I'm not hurrying so I can wait until fixing #285 that seems to fundamentally solve the problem.

[deadprogram]

These seems some confusion.

The bug mentioned has nothing to do with the bytealg.CountString feature. it is that you cannot use the //go:linkname directive outside of the runtime package, which is not really related to the bytealg.CountString feature in this issue.

#285 has nothing directly to do with your issue.

I hope that clarifies.

[deadprogram]

My own PR that implemented this based on your research @1l0 was merged into dev thanks for working on this. Now closing.