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x/tools/go/analysis/passes/copylock: allows assignment of composite literal with a "lock" #43044

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ghananigans opened this issue Dec 7, 2020 · 6 comments
Open

x/tools/go/analysis/passes/copylock: allows assignment of composite literal with a "lock" #43044

ghananigans opened this issue Dec 7, 2020 · 6 comments
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Analysis Issues related to static analysis (vet, x/tools/go/analysis) NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Tools This label describes issues relating to any tools in the x/tools repository.
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Unreleased

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@ghananigans
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ghananigans commented Dec 7, 2020 •
edited

The copylocks checker does not complain about

var a nonCopyableType
...
a = nonCopyableType{}

but does complain about

var a nonCopyableType
var b nonCopyableType
...
a = b

(as expected).

nonCopyableType looks something like:

type nonCopyableType struct {
    _ sync.NoCopy

    ...
}

where sync.NoCopy is
https://github.com/google/gvisor/blob/a97ceec01bc464c9efa5d8140906c46f637e9002/pkg/sync/nocopy.go#L22

I think this is because of

go/src/cmd/vendor/golang.org/x/tools/go/analysis/passes/copylock/copylock.go

Line 74 in e10c94a

func checkCopyLocksAssign(pass *analysis.Pass, as *ast.AssignStmt) {
which allows assignment with a rhs composite literal, while ignoring the lhs.
@stamblerre stamblerre changed the title copylocks allows assignment of composite literal with a "lock" x/tools/go/analysis/passes/copylock: allows assignment of composite literal with a "lock" Dec 7, 2020
@stamblerre
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/cc @matloob

@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Dec 7, 2020
@gopherbot gopherbot added this to the Unreleased milestone Dec 7, 2020
@cagedmantis cagedmantis added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Dec 7, 2020
@josharian
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Writing a zero value is both safe and useful. I believe that this is working as intended.

@tamird
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tamird commented Dec 8, 2020 via email

@josharian
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It is.

@tamird
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tamird commented Dec 8, 2020

What? How can that possibly be safe? This is reproducible on the playground: https://play.golang.org/p/ZW9TPnAnEcQ

@josharian
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What? How can that possibly be safe?

Instead of rhetorical questions, it would help to be concrete. What is unsafe about it? As long as the write isn't concurrent (which is the race detector's domain), you are opting to reset the mutex to a clean, unlocked state.

@adonovan adonovan added the Analysis Issues related to static analysis (vet, x/tools/go/analysis) label Apr 23, 2023
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Analysis Issues related to static analysis (vet, x/tools/go/analysis) NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Tools This label describes issues relating to any tools in the x/tools repository.
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@josharian @cagedmantis @tamird @adonovan @stamblerre @ghananigans @gopherbot