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gccgo: fails to reject unsafe.Offsetof(*&(s.f)) #40291

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mdempsky opened this issue Jul 19, 2020 · 0 comments
Open

gccgo: fails to reject unsafe.Offsetof(*&(s.f)) #40291

mdempsky opened this issue Jul 19, 2020 · 0 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Gccgo

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@mdempsky
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mdempsky commented Jul 19, 2020 •
edited

This source code is rejected by cmd/compile and go/types, but prints 0 when run using gccgo:

package main

import "unsafe"

var s struct{ f float64 }

func main() {
	println(unsafe.Offsetof(*&(s.f)))
}

It seems like gccgo is optimizing *&(s.f) to (s.f) before checking that the argument to unsafe.Offsetof is well formed.

/cc @ianlancetaylor

Edit: I think the same issue affects unsafe.Alignof too.
@mdempsky mdempsky added this to the Gccgo milestone Jul 19, 2020
@toothrot toothrot added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jul 21, 2020
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