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cmd/compile: missing "out of bounds" error slicing [0]T #20749

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josharian opened this issue Jun 22, 2017 · 5 comments
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cmd/compile: missing "out of bounds" error slicing [0]T #20749

josharian opened this issue Jun 22, 2017 · 5 comments
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Go1.9

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@josharian
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package p

func f() {
	var b [0]struct{}
	_ = b[2:]
}

gotype says:

x.go:5:8: index 2 (constant of type int) is out of bounds

cmd/compile gives no error. If you change b's type to [1]struct{}, the error from cmd/compile is:

x.go:5: invalid slice index 2 (out of bounds for 1-element array)

Reproduces with (at least) 1.7 and 1.8 and 1.9beta1.
@josharian josharian added this to the Go1.10 milestone Jun 22, 2017
@josharian
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Found with go-fuzz.

@ianlancetaylor
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gccgo says

foo8.go:5:8: error: array index out of bounds
  _ = b[2:]
        ^

@griesemer
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This is clearly a cmp/compile bug. Interestingly, the compiler complains for an index expression (b[2]) rather than a slice expression (b[2:]).

@griesemer griesemer self-assigned this Jun 22, 2017
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Trivial fix. Moving to 1.9.

@griesemer griesemer modified the milestones: Go1.9, Go1.10 Jun 22, 2017
@gopherbot
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CL https://golang.org/cl/46466 mentions this issue.

@golang golang locked and limited conversation to collaborators Jun 22, 2018
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@josharian @ianlancetaylor @griesemer @gopherbot