go-fuzz-build fails on github.com/robfig/soy

[robfig]

Thanks for your amazing work on fuzz testing!

I tried to use go-fuzz to test github.com/robfig/soy, but I ended up with a Go compile error from the instrumented code. It seems like there is some scenario that's not handled correctly in go-fuzz-build.

Source code that triggers the error:

func funcIsNonnull(v []data.Value) data.Value {
	return data.Bool(!(v[0] == data.Null{} || v[0] == data.Undefined{}))
}

Instrumented code, with //line comments stripped for readability:

func funcIsNonnull(v []data.Value) data.Value {
	_go_fuzz_dep_.CoverTab[32995]++
	return data.Bool(!(func() bool {
		__gofuzz_v1 := v[0]
		__gofuzz_v2 := data.Null{}
		_go_fuzz_dep_.Sonar(__gofuzz_v1, __gofuzz_v2, 1496832)
		return __gofuzz_v1 == __gofuzz_v2
	}() == true || func() github.com/robfig/soy/data.Bool {
		_go_fuzz_dep_.CoverTab[17175]++
		return func() bool {
			__gofuzz_v1 := v[0]
			__gofuzz_v2 := data.Undefined{}
			_go_fuzz_dep_.Sonar(__gofuzz_v1, __gofuzz_v2, 1497088)
			return __gofuzz_v1 == __gofuzz_v2
		}() == true
	}()))
}

Compile error:

$ go-fuzz-build -work github.com/robfig/soy
workdir: /var/folders/hq/22l_y9yn3llfhj91mvk913xm0000gn/T/go-fuzz-build263099547
workdir: /var/folders/hq/22l_y9yn3llfhj91mvk913xm0000gn/T/go-fuzz-build281538366
failed to execute go build: exit status 2
# github.com/robfig/soy/soyhtml
.../soy/soyhtml/funcs.go:57: syntax error: unexpected ++, expecting comma or }
.../soy/soyhtml/funcs.go:57: syntax error: unexpected return, expecting )
.../soy/soyhtml/funcs.go:57: syntax error: unexpected ( after top level declaration

This line looks like the error to me, due to using the entire import path rather than just the package name:

func() github.com/robfig/soy/data.Bool {

I have pushed the code I'm working with on the "fuzz" branch:
https://github.com/robfig/soy/tree/fuzz

Let me know if I can provide anything else.
Thanks,
Rob

[dvyukov]

I can reproduce this and I added a small test case, but I am not sure when I will have time to fix this.
Another reason to remember golang/go#19109