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[clang-tidy] support return c ? a : b; in bugprone-return-const-ref-from-parameter #107657

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Merged
merged 3 commits into from
Oct 31, 2024
Merged

[clang-tidy] support return c ? a : b; in bugprone-return-const-ref-from-parameter #107657

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b00b02b
[clang-tidy] support `return c ? a : b;` in bugprone-return-const-ref…
5chmidti Sep 6, 2024
1c3d627
the conditional operator has to be the returned value
5chmidti Oct 9, 2024
f47238f
ignore parens for the DeclRefExpr of the parameter
5chmidti Oct 10, 2024
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37 changes: 21 additions & 16 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 @@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//

#include "ReturnConstRefFromParameterCheck.h"
#include "clang/AST/Expr.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"

Expand All @@ -15,20 +16,24 @@ using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {

void ReturnConstRefFromParameterCheck::registerMatchers(MatchFinder *Finder) {
Finder->addMatcher(
returnStmt(
hasReturnValue(declRefExpr(
to(parmVarDecl(hasType(hasCanonicalType(
qualType(lValueReferenceType(pointee(
qualType(isConstQualified()))))
.bind("type"))))
.bind("param")))),
hasAncestor(
functionDecl(hasReturnTypeLoc(loc(qualType(
hasCanonicalType(equalsBoundNode("type"))))))
.bind("func")))
.bind("ret"),
this);
const auto DRef =
declRefExpr(
to(parmVarDecl(hasType(hasCanonicalType(
qualType(lValueReferenceType(pointee(
qualType(isConstQualified()))))
.bind("type"))))
.bind("param")))
.bind("dref");
const auto Func =
functionDecl(hasReturnTypeLoc(loc(
qualType(hasCanonicalType(equalsBoundNode("type"))))))
.bind("func");

Finder->addMatcher(returnStmt(hasReturnValue(DRef), hasAncestor(Func)), this);
Finder->addMatcher(conditionalOperator(eachOf(hasTrueExpression(DRef),
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return should also in this pattern. we should not warn for the condition expression, instead, we should warn for return c?a:b

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Done. I've also wrapped the conditionalOperator inside an ignoresParens

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@5chmidti 5chmidti Oct 10, 2024 •
edited
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I've also wrapped the conditionalOperator inside an ignoresParens

  • Added ignoreParens around the declRefExpr matcher.

Maybe these should be done as a new commit? WDYT?

hasFalseExpression(DRef)),
hasAncestor(Func)),
this);
}

static bool isSameTypeIgnoringConst(QualType A, QualType B) {
Expand Down Expand Up @@ -85,8 +90,8 @@ void ReturnConstRefFromParameterCheck::check(
const MatchFinder::MatchResult &Result) {
const auto *FD = Result.Nodes.getNodeAs<FunctionDecl>("func");
const auto *PD = Result.Nodes.getNodeAs<ParmVarDecl>("param");
const auto *R = Result.Nodes.getNodeAs<ReturnStmt>("ret");
const SourceRange Range = R->getRetValue()->getSourceRange();
const auto *DRef = Result.Nodes.getNodeAs<DeclRefExpr>("dref");
const SourceRange Range = DRef->getSourceRange();
if (Range.isInvalid())
return;

Expand Down
5 changes: 5 additions & 0 deletions clang-tools-extra/docs/ReleaseNotes.rst
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Expand Up @@ -137,6 +137,11 @@ Changes in existing checks
<clang-tidy/checks/bugprone/posix-return>` check to support integer literals
as LHS and posix call as RHS of comparison.

- 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``.

- Improved :doc:`bugprone-sizeof-expression
<clang-tidy/checks/bugprone/sizeof-expression>` check to find suspicious
usages of ``sizeof()``, ``alignof()``, and ``offsetof()`` when adding or
Expand Down
9 changes: 9 additions & 0 deletions clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp
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Expand Up @@ -27,6 +27,10 @@ int const &f3(TConstRef a) { return a; }
int const &f4(TConst &a) { return a; }
// CHECK-MESSAGES: :[[@LINE-1]]:35: warning: returning a constant reference parameter

int const &f5(TConst &a) { return true ? a : a; }
// CHECK-MESSAGES: :[[@LINE-1]]:42: warning: returning a constant reference parameter
// CHECK-MESSAGES: :[[@LINE-2]]:46: warning: returning a constant reference parameter

template <typename T>
const T& tf1(const T &a) { return a; }
// CHECK-MESSAGES: :[[@LINE-1]]:35: warning: returning a constant reference parameter
Expand All @@ -47,6 +51,11 @@ template <typename T>
const T& itf4(typename ConstRef<T>::type a) { return a; }
// CHECK-MESSAGES: :[[@LINE-1]]:54: warning: returning a constant reference parameter

template <typename T>
const T& itf5(const T &a) { return true ? a : a; }
// CHECK-MESSAGES: :[[@LINE-1]]:43: warning: returning a constant reference parameter
// CHECK-MESSAGES: :[[@LINE-2]]:47: warning: returning a constant reference parameter

void instantiate(const int &param, const float &paramf, int &mut_param, float &mut_paramf) {
itf1(0);
itf1(param);
Expand Down
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