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cmd/compile,debug/gosym: generics: compiler produces symbols that gosym can not parse #48032

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aarzilli opened this issue Aug 28, 2021 · 3 comments
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@aarzilli
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@aarzilli aarzilli commented Aug 28, 2021

The symbol names currently produced by the compiler for generic function instantiations can not be parsed by debug/gosym (or any simple parser for that matter).

For example:

func testfunction[T any](arg T) {
	fmt.Println(arg)
}

func main() {
	testfunction(3)
}

Produces the symbol main.testfunction[.shape.int] for which gosym will return:

PackageName: "main"
ReceiverName: "testfunction[.shape"
BaseName: "int]"

instead of:

PackageName: "main"
ReceiverName: ""
BaseName: "testfunction[.shape.int]"

Parsing symbol names is further complicated by generic method instantiations:

type S[T any] struct {
	x T
}

func (s *S[T]) testfunction() {
	fmt.Println(s.x)
}

Will produce the symbol main.(*S[.shape.int]).testfunction, so just looking for the first . instead of the last one doesn't work either.

Referencing issue #37762 here since its making an effort to fix a bug in this area.

@cherrymui cherrymui changed the title cmd/compile,debug/gosym: compiler produces symbols that gosym can not parse cmd/compile,debug/gosym: generics: compiler produces symbols that gosym can not parse Aug 30, 2021
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@cherrymui cherrymui commented Aug 30, 2021

cc @griesemer @randall77 @danscales

@cherrymui cherrymui added the NeedsFix label Aug 30, 2021
@cherrymui cherrymui added this to the Go1.18 milestone Aug 30, 2021
@danscales
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@danscales danscales commented Aug 30, 2021

@griesemer and I talked. Once some types2 change are complete that will give a better unique name for various types (in a week or two), we will discuss gosym compatibility and other issues related to naming instantiations of generic functions/methods, and come to a more formal decision on the format of names of function instantiations.

In this case, as you describe, the '.' that we are using when specifying the type args of a function instantiation is clearly confusing the current gosym code.

@gopherbot
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@gopherbot gopherbot commented Oct 7, 2021

Change https://golang.org/cl/354689 mentions this issue: cmd/compile: adjust debug/gosym to deal with instantiated types/funcs/methods

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