[clang-tools-extra] [clang-tidy]avoid bugprone-unused-return-value false positive for assignment operator overloading (PR #84489)
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Fri Mar 8 06:19:07 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-tidy
Author: Congcong Cai (HerrCai0907)
<details>
<summary>Changes</summary>
Fixes: #<!-- -->84480
We assuem assignemnt at most of time, operator overloading means the value is assigned to the other variable, then clang-tidy should suppress warning even if this operator overloading match the regex.
---
Full diff: https://github.com/llvm/llvm-project/pull/84489.diff
3 Files Affected:
- (modified) clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp (+14-10)
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+2-2)
- (added) clang-tools-extra/test/clang-tidy/checkers/bugprone/unused-return-value-avoid-assignment.cpp (+31)
``````````diff
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
index 1252b2f23805a1..2167d381c42b03 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
@@ -11,6 +11,7 @@
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
using namespace clang::ast_matchers;
using namespace clang::ast_matchers::internal;
@@ -157,16 +158,19 @@ void UnusedReturnValueCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
}
void UnusedReturnValueCheck::registerMatchers(MatchFinder *Finder) {
- auto MatchedDirectCallExpr =
- expr(callExpr(callee(functionDecl(
- // Don't match void overloads of checked functions.
- unless(returns(voidType())),
- anyOf(isInstantiatedFrom(matchers::matchesAnyListedName(
- CheckedFunctions)),
- returns(hasCanonicalType(hasDeclaration(
- namedDecl(matchers::matchesAnyListedName(
- CheckedReturnTypes)))))))))
- .bind("match"));
+ auto MatchedDirectCallExpr = expr(
+ callExpr(callee(functionDecl(
+ // Don't match void overloads of checked functions.
+ unless(returns(voidType())),
+ // Don't match copy or move assignment operator.
+ unless(cxxMethodDecl(anyOf(isCopyAssignmentOperator(),
+ isMoveAssignmentOperator()))),
+ anyOf(isInstantiatedFrom(
+ matchers::matchesAnyListedName(CheckedFunctions)),
+ returns(hasCanonicalType(hasDeclaration(
+ namedDecl(matchers::matchesAnyListedName(
+ CheckedReturnTypes)))))))))
+ .bind("match"));
auto CheckCastToVoid =
AllowCastToVoid ? castExpr(unless(hasCastKind(CK_ToVoid))) : castExpr();
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index b5f025ce467a15..c7121fe07e0ad3 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -152,9 +152,9 @@ Changes in existing checks
- Improved :doc:`bugprone-unused-return-value
<clang-tidy/checks/bugprone/unused-return-value>` check by updating the
- parameter `CheckedFunctions` to support regexp and avoiding false postive for
+ parameter `CheckedFunctions` to support regexp, avoiding false positive for
function with the same prefix as the default argument, e.g. ``std::unique_ptr``
- and ``std::unique``.
+ and ``std::unique``, avoiding false positive for assignment operator overloading.
- Improved :doc:`bugprone-use-after-move
<clang-tidy/checks/bugprone/use-after-move>` check to also handle
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unused-return-value-avoid-assignment.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unused-return-value-avoid-assignment.cpp
new file mode 100644
index 00000000000000..8bd3c30e71b51a
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unused-return-value-avoid-assignment.cpp
@@ -0,0 +1,31 @@
+// RUN: %check_clang_tidy %s bugprone-unused-return-value %t \
+// RUN: -config='{CheckOptions: \
+// RUN: {bugprone-unused-return-value.CheckedFunctions: "::*"}}' \
+// RUN: --
+
+struct S {
+ S(){};
+ S(S const &);
+ S(S &&);
+ S &operator=(S const &);
+ S &operator=(S &&);
+};
+
+S returnValue();
+S const &returnRef();
+
+void bar() {
+ returnValue();
+ // CHECK-MESSAGES: [[@LINE-1]]:3: warning: the value returned by this function should not be disregarded; neglecting it may lead to errors
+
+ S a{};
+ a = returnValue();
+ // CHECK-NOT: [[@LINE-1]]:3: warning
+ a.operator=(returnValue());
+ // CHECK-NOT: [[@LINE-1]]:3: warning
+
+ a = returnRef();
+ // CHECK-NOT: [[@LINE-1]]:3: warning
+ a.operator=(returnRef());
+ // CHECK-NOT: [[@LINE-1]]:3: warning
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/84489
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