infinite recursion trying to create recursive function type

[dgryski]

Tinygo does not like fnType in the below program:

package main

type fnType func(int) (fnType, error)

func printNode(int) (fnType, error) {
        return nil, nil
}

func main() {
}

tinygo errors with a stack overflow; the callstack is filled with

	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/func.go:99 +0x8c fp=0xc020d40560 sp=0xc020d40520 pc=0x429c7ec
github.com/tinygo-org/tinygo/compiler.(*compilerContext).makeLLVMType(0xc0005b0000, {0x4413240, 0xc000ca67e0})
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/compiler.go:388 +0x2b4 fp=0xc020d40628 sp=0xc020d40560 pc=0x4284cd4
github.com/tinygo-org/tinygo/compiler.(*compilerContext).getLLVMType(0xc0005b0000, {0x4413240, 0xc000ca67e0})
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/compiler.go:321 +0x6e fp=0xc020d40668 sp=0xc020d40628 pc=0x428498e
github.com/tinygo-org/tinygo/compiler.(*compilerContext).makeLLVMType(0xc0005b0000, {0x44131f0, 0xc000128e80})
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/compiler.go:383 +0x771 fp=0xc020d40730 sp=0xc020d40668 pc=0x4285191
github.com/tinygo-org/tinygo/compiler.(*compilerContext).getLLVMType(0xc0005b0000, {0x44131f0, 0xc000128e80})
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/compiler.go:321 +0x6e fp=0xc020d40770 sp=0xc020d40730 pc=0x428498e
github.com/tinygo-org/tinygo/compiler.(*compilerContext).getRawFuncType(0xc0005b0000, 0xc000ca67e0)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/compiler/func.go:125 +0x4cf fp=0xc020d40828 sp=0xc020d40770 pc=0x429cd4f
github.com/tinygo-org/tinygo/compiler.(*compilerContext).getFuncType(0xc0005b0000, 0x0)

[dgryski]

Interesting; this doesn't fail on dev, only on my local branch consisting of dev + #2011 + #2171

Bisecting shows c722426 as the first bad commit.

[dgryski]

This triggers on dev when building for native. The coroutine-logic prevents it from hitting wasm on dev, but does cause it to trigger for asyncify.

[aykevl]

Yeah, I've been aware of this bug for a long time but somehow nobody triggered it, so I was hoping it would never happen.

The issue here is that the function pointer type here is recursive: it has a parameter with a pointer to itself. But you probably figured that out already. Unfortunately, I'm not aware of any way to construct such a type in LLVM: the only type that allows such recursion are structs.

[aykevl]

This doesn't normally happen on WebAssembly because function pointers are implemented differently there. Check FuncImplementation. Picking the other one might be a temporary workaround.

[aykevl]

Here is a fix: #2175

[deadprogram]

I think the request was fulfilled in the new release, so closing. Please reopen if needed. Thanks!