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gccgo: does not error on unused var #12317

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dvyukov opened this issue Aug 25, 2015 · 4 comments
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gccgo: does not error on unused var #12317

dvyukov opened this issue Aug 25, 2015 · 4 comments
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Gccgo

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@dvyukov
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dvyukov commented Aug 25, 2015

gccgo successfully compiles the following incorrect program:

package a
func g() {
    var f = func() {}
}

Both gc and gotype say:

test.go:3:6: f declared but not used

gofrontend is on commit 81810917af7ba19e1f9f8efc8b1989f7d6419d30
@dvyukov
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dvyukov commented Aug 25, 2015

@ianlancetaylor

@cespare
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cespare commented Aug 25, 2015

That program is not incorrect. From the spec:

Implementation restriction: A compiler may make it illegal to declare a variable inside a function body if the variable is never used.

So gccgo is free to allow the unused var.

I'm not sure whether gccgo disallows other unused vars, though (don't have a gccgo installation available right now).

@paranoiacblack paranoiacblack added this to the Gccgo milestone Aug 25, 2015
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This is a gccgo bug; it doesn't check if variables initialized by a function literal are ever used. I don't think this is on purpose, despite the disclaimer in the specification.

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CL https://golang.org/cl/13908 mentions this issue.

pbeeler pushed a commit to SaberMod/GCC_SaberMod that referenced this issue Aug 28, 2015
compiler: Report unused variables initialized to function literals.
9f2ed78 
    
    Fixes golang/go#12317.
    
    Reviewed-on: https://go-review.googlesource.com/13908


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@227285 138bc75d-0d04-0410-961f-82ee72b054a4
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