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x/tools/go/analysis/passes/nilness: check pointers inside structs as well #43301

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ainar-g opened this issue Dec 21, 2020 · 2 comments
Open

x/tools/go/analysis/passes/nilness: check pointers inside structs as well #43301

ainar-g opened this issue Dec 21, 2020 · 2 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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@ainar-g
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ainar-g commented Dec 21, 2020

nilness currently (as of golang/tools@ae774e9781d2 with Go 1.15.6) correctly reports this issue:

if pmax == nil {
        max = *pmax
}

But not this one:

if v.max == nil {
        max = *v.max
}

Full reproduction code.
@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Dec 21, 2020
@gopherbot gopherbot added this to the Unreleased milestone Dec 21, 2020
@ainar-g ainar-g changed the title x/tools/go/analysis/passes/nilness: check pointers insite structs as well x/tools/go/analysis/passes/nilness: check pointers inside structs as well Dec 21, 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 21, 2020
@cagedmantis
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/cc @matloob

@adonovan
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This would require implementing the GVN (global value numbering) optimization in golang.org/x/tools/go/ssa to recognize that both occurrences of the repeated expression v.max must have the same value. This is not trivial in general: any operations in between the two statements could change the address of v, or assign to its max field.

@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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@cagedmantis @ainar-g @adonovan @gopherbot