Support fuzzing unexported fields

[yanzhoupan]

The current gofuzz only support fuzzing the exported fields (i.e. the fields that start with an uppercase letter), other fields are simply filtered out according to this line.

However, a lot of struct also contains un-exported fields (i.e. fields start with lowercase letters) and sometimes people want to do fuzzing on those structs. In this pr I fixed this problem by adding allowUnexportedFields to the fuzzer, which allows user to decide whether they want to include unexported fields while fuzzing. It is set to false by default. But it can be turned on with AllowUnexportedFields function.

Tests are also added.

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[yanzhoupan]

@googlebot I signed it!

[lavalamp]

Make sure the field is addressable -- I think it always should be but verifying seems good.

Suggested change

	if fc.fuzzer.allowUnexportedFields{
	if fc.fuzzer.allowUnexportedFields && v.CanAddr() {

[yanzhoupan]

Hi Daniel,
Thanks for the suggestion! I added that

[lavalamp]

Please run gofmt

[yanzhoupan]

Just did gofmt, please checkout the latest files

[lavalamp]

Sorry I was too slow making this comment -- can you flip the logic around on this?

if !fc.fuzzer.allowUnexportedFields || !v.CanAddr() {
  return
}
v = reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr())).Elem()

This reduces the indentation. Minor style nit.

[yanzhoupan]

No problem! I just did that.
And all tests passed

[lavalamp]

LGTM, I'll double check the tests in a bit because the CI integration seems to be off or not working.

[yanzhoupan]

LGTM, I'll double check the tests in a bit because the CI integration seems to be off or not working.

Cool! Looking forward to my first contribution to google lol

[lavalamp]

Thanks for the change!