Segmentation fault compiling to WASM

[upsj]

I am trying to build a WASM plugin for the D2 diagram framework to be used as a plugin in Typst. The compilation is failing with a segmentation violation in the compiler:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x38 pc=0x103250730]

goroutine 918 [running]:
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402b3484b0, {0x1402928cf10, 0x6, 0x14033c61b60?}, 0x1400bfff050, {0x1402463a570, 0x28})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:361 +0x34e0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fef0, {0x1400abfdf10, 0x2, 0x14033c60210?}, 0x1400bfbd410, {0x1402463a4b0, 0x24})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fea0, {0x1400ab5c290, 0x3, 0x14033c5b740?}, 0x1400bfaa630, {0x140144c0120, 0x20})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fe00, {0x1400a009a10, 0x2, 0x14033c556f8?}, 0x1400bf7ec90, {0x140143ff660, 0x1c})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fdb0, {0x1400820a990, 0x2, 0x14033c53a58?}, 0x1400b9da3c0, {0x1402b751278, 0x18})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fd60, {0x1402c905790, 0x2, 0x14033b4f728?}, 0x1400b6f8360, {0x1400d52df08, 0x14})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fa90, {0x1402c6bd790, 0x5, 0x108e21220?}, 0x1400ada4c00, {0x14032339310, 0x10})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97fa40, {0x1402bef0710, 0x5, 0x108e21220?}, 0x14010b2da40, {0x1402701c7a0, 0xc})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402c97f720, {0x1402b41bf10, 0x5, 0x108e21220?}, 0x1402b37c690, {0x14032ae3240, 0x8})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.(*runner).run(0x14029f52000, 0x1402b408f50, {0x0, 0x0, 0x1?}, 0x0, {0x107690906, 0x4})
        /Users/runner/work/tinygo/tinygo/interp/interpreter.go:552 +0x67d0
github.com/tinygo-org/tinygo/interp.Run({0x139b120e0?}, 0x29e8d60800?, 0x0?)
        /Users/runner/work/tinygo/tinygo/interp/interp.go:121 +0x4dc
github.com/tinygo-org/tinygo/builder.optimizeProgram({0x361adc400?}, 0x14000132100, 0x1400026c630)
        /Users/runner/work/tinygo/tinygo/builder/build.go:1114 +0x3c
github.com/tinygo-org/tinygo/builder.Build.func5(0x1402c9348a0?)
        /Users/runner/work/tinygo/tinygo/builder/build.go:583 +0x4b0
github.com/tinygo-org/tinygo/builder.runJob(0x1402c934900, 0x1402c98c000)
        /Users/runner/work/tinygo/tinygo/builder/jobs.go:212 +0x48
created by github.com/tinygo-org/tinygo/builder.runJobs in goroutine 1
        /Users/runner/work/tinygo/tinygo/builder/jobs.go:113 +0x43c

To reproduce this, place the following file in the root of a cloned D2 repository https://github.com/terrastruct/d2 and try to compile it with

GOOS=wasip1 GOARCH=wasm tinygo build -buildmode=c-shared -o example.wasm example.go

package main

import (
	"context"
	"unsafe"

	"oss.terrastruct.com/d2/d2graph"
	"oss.terrastruct.com/d2/d2layouts/d2dagrelayout"
	"oss.terrastruct.com/d2/d2lib"
	"oss.terrastruct.com/d2/d2renderers/d2svg"
	"oss.terrastruct.com/d2/d2themes/d2themescatalog"
	"oss.terrastruct.com/d2/lib/textmeasure"
	"oss.terrastruct.com/util-go/go2"
)

//go:wasmimport typst_env wasm_minimal_protocol_write_args_to_buffer
func wasm_minimal_protocol_write_args_to_buffer(ptr unsafe.Pointer)

//go:wasmimport typst_env wasm_minimal_protocol_send_result_to_host
func wasm_minimal_protocol_send_result_to_host(ptr unsafe.Pointer, size int32)

//go:wasmexport example
func example(input_size int32) int32 {
	input := make([]byte, input_size)
	wasm_minimal_protocol_write_args_to_buffer(unsafe.Pointer(&input[0]))
	ruler, _ := textmeasure.NewRuler()
	layoutResolver := func(engine string) (d2graph.LayoutGraph, error) {
		return d2dagrelayout.DefaultLayout, nil
	}
	renderOpts := &d2svg.RenderOpts{
		Pad:     go2.Pointer(int64(5)),
		ThemeID: &d2themescatalog.GrapeSoda.ID,
	}
	compileOpts := &d2lib.CompileOptions{
		LayoutResolver: layoutResolver,
		Ruler:          ruler,
	}
	diagram, _, _ := d2lib.Compile(context.Background(), "x -> y", compileOpts, renderOpts)
	output, _ := d2svg.Render(diagram, renderOpts)
	wasm_minimal_protocol_send_result_to_host(unsafe.Pointer(&output[0]), int32(len(output)))
	return 0
}

func main() {}

Hardware:
M2 Mac

Version:

 tinygo version 0.34.0 darwin/arm64 (using go version go1.23.3 and LLVM version 18.1.2)

[upsj]

The issue also occurs on a x86_64 system with version

tinygo version 0.34.0 linux/amd64 (using go version go1.23.1 and LLVM version 18.1.2)

Unfortunately I know too little about go debugging to be able to track down which function causes these issues, but it seems to be related to compile-time evaluation of initialization functions.

[dgryski]

We should probably add a -internal-interp-debug flag that spits out which package is trying to be compiled during the interp phase. I had a patch somewhere that did that, but I can clean it up again and make it actually useful rather than just a hack.

[aykevl]

@dgryski yes sounds like a good idea!

@upsj I have reproduced this issue, but haven't looked into it further yet.