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[clang-tidy] fix false positive in bugprone-return-const-ref-from-parameter #117734

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Nov 30, 2024
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[clang-tidy] fix false positive in bugprone-return-const-ref-from-parameter #117734

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6 changes: 4 additions & 2 deletions clang-tools-extra/clang-tidy/bugprone/ReturnConstRefFromParameterCheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,11 +21,13 @@ void ReturnConstRefFromParameterCheck::registerMatchers(MatchFinder *Finder) {
to(parmVarDecl(hasType(hasCanonicalType(
qualType(lValueReferenceType(pointee(
qualType(isConstQualified()))))
.bind("type"))))
.bind("type"))),
hasDeclContext(functionDecl().bind("owner")))
.bind("param")))
.bind("dref"));
const auto Func =
functionDecl(hasReturnTypeLoc(loc(
functionDecl(equalsBoundNode("owner"),
hasReturnTypeLoc(loc(
qualType(hasCanonicalType(equalsBoundNode("type"))))))
.bind("func");

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3 changes: 2 additions & 1 deletion clang-tools-extra/docs/ReleaseNotes.rst
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Expand Up @@ -179,7 +179,8 @@ Changes in existing checks
- Improved :doc:`bugprone-return-const-ref-from-parameter
<clang-tidy/checks/bugprone/return-const-ref-from-parameter>` check to
diagnose potential dangling references when returning a ``const &`` parameter
by using the conditional operator ``cond ? var1 : var2``.
by using the conditional operator ``cond ? var1 : var2`` and no longer giving
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@HerrCai0907 HerrCai0907 Nov 28, 2024

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I am not sure it is a fix of false positives. Maybe in generic, it more looks like add support of lambda function.

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@jcsxky jcsxky Nov 29, 2024

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The function in this issue contains lambda and thus gives a false positive(because it should not report diagnose since the return statement is not belongs to current function). I have modified the release note and make it easier to be understood.

false positives for functions which contain lambda.

- Improved :doc:`bugprone-sizeof-expression
<clang-tidy/checks/bugprone/sizeof-expression>` check to find suspicious
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11 changes: 11 additions & 0 deletions clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp
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Expand Up @@ -76,6 +76,9 @@ struct C {
// CHECK-MESSAGES: :[[@LINE-1]]:38: warning: returning a constant reference parameter
};

const auto Lf1 = [](const T& t) -> const T& { return t; };
// CHECK-MESSAGES: :[[@LINE-1]]:54: warning: returning a constant reference parameter

} // namespace invalid

namespace false_negative_because_dependent_and_not_instantiated {
Expand Down Expand Up @@ -151,6 +154,14 @@ void instantiate(const int &param, const float &paramf, int &mut_param, float &m
itf6(mut_paramf);
}

template<class T>
void f(const T& t) {
const auto get = [&t] -> const T& { return t; };
return T{};
}
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@PiotrZSL PiotrZSL Nov 26, 2024

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Please add test:

const auto get = [](const T& t2) -> const T& { return t2; };

and verify that it's being still detected.

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@jcsxky jcsxky Nov 28, 2024

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Done.


const auto Lf1 = [](T& t) -> const T& { return t; };

} // namespace valid

namespace overload {
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