llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-tidy
Author: Vitaly Goldshteyn (goldvitaly)
<details>
<summary>Changes</summary>
Clang-Tidy unnecessary-value-param value param will be triggered for
templated functions if at least one instantiontion with expensive to
copy type is present in translation unit.
It is relatively common mistake to write lambda functions with auto
arguments for expensive to copy types.
Example:
Copy of the vectors will happen on every comparison.
```
void SortBySize(std::vector<std::vector<int>>& a) {
std::sort(
a.begin(), a.end(),
[](auto x, auto y) { return a.size() < b.size()});
}
```
---
Full diff: https://github.com/llvm/llvm-project/pull/97767.diff
3 Files Affected:
- (modified)
clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp (+2-5)
- (added)
clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param-templates.cpp
(+92)
- (modified)
clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp
(-45)
``````````diff
diff --git
a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
index c507043c367a8..fe8cc11018e1e 100644
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
@@ -75,7 +75,7 @@ void UnnecessaryValueParamCheck::registerMatchers(MatchFinder
*Finder) {
functionDecl(hasBody(stmt()), isDefinition(), unless(isImplicit()),
unless(cxxMethodDecl(anyOf(isOverride(), isFinal()))),
has(typeLoc(forEach(ExpensiveValueParamDecl))),
- unless(isInstantiated()), decl().bind("functionDecl"))),
+ decl().bind("functionDecl"))),
this);
}
@@ -133,12 +133,9 @@ void UnnecessaryValueParamCheck::check(const
MatchFinder::MatchResult &Result) {
// 2. the function is virtual as it might break overrides
// 3. the function is referenced outside of a call expression within the
// compilation unit as the signature change could introduce build errors.
- // 4. the function is a primary template or an explicit template
- // specialization.
const auto *Method = llvm::dyn_cast<CXXMethodDecl>(Function);
if (Param->getBeginLoc().isMacroID() || (Method && Method->isVirtual()) ||
- isReferencedOutsideOfCallExpr(*Function, *Result.Context) ||
- (Function->getTemplatedKind() != FunctionDecl::TK_NonTemplate))
+ isReferencedOutsideOfCallExpr(*Function, *Result.Context))
return;
for (const auto *FunctionDecl = Function; FunctionDecl != nullptr;
FunctionDecl = FunctionDecl->getPreviousDecl()) {
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param-templates.cpp
b/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param-templates.cpp
new file mode 100644
index 0000000000000..4e6ec401f17c8
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param-templates.cpp
@@ -0,0 +1,92 @@
+// RUN: %check_clang_tidy -std=c++14-or-later %s
performance-unnecessary-value-param %t
+
+struct ExpensiveToCopyType {
+ virtual ~ExpensiveToCopyType();
+};
+
+template <typename T> void templateWithNonTemplatizedParameter(const
ExpensiveToCopyType S, T V) {
+ // CHECK-MESSAGES: [[@LINE-1]]:90: warning: the const qualified parameter 'S'
+ // CHECK-MESSAGES: [[@LINE-2]]:95: warning: the parameter 'V'
+ // CHECK-FIXES: template <typename T> void
templateWithNonTemplatizedParameter(const ExpensiveToCopyType& S, const T& V) {
+}
+
+void instantiatedWithExpensiveValue() {
+ templateWithNonTemplatizedParameter(
+ ExpensiveToCopyType(), ExpensiveToCopyType());
+ templateWithNonTemplatizedParameter(ExpensiveToCopyType(), 5);
+}
+
+template <typename T> void
templateWithNonTemplatizedParameterCheapTemplate(const ExpensiveToCopyType S, T
V) {
+ // CHECK-MESSAGES: [[@LINE-1]]:103: warning: the const qualified parameter
'S'
+ // CHECK-FIXES: template <typename T> void
templateWithNonTemplatizedParameterCheapTemplate(const ExpensiveToCopyType& S,
T V) {
+}
+
+void instantiatedWithCheapValue() {
+ templateWithNonTemplatizedParameterCheapTemplate(ExpensiveToCopyType(), 5);
+}
+
+template <typename T> void nonInstantiatedTemplateWithConstValue(const T S) {}
+template <typename T> void nonInstantiatedTemplateWithNonConstValue(T S) {}
+
+template <typename T> void instantiatedTemplateSpecialization(T NoSpecS) {}
+template <>
+void instantiatedTemplateSpecialization<ExpensiveToCopyType>(
+ ExpensiveToCopyType SpecS) {
+ // CHECK-MESSAGES: [[@LINE-1]]:25: warning: the parameter 'SpecS'
+ // CHECK-FIXES: const T& NoSpecS
+ // CHECK-FIXES: const ExpensiveToCopyType& SpecS
+}
+
+void instantiatedTemplateSpecialization() {
+ instantiatedTemplateSpecialization(ExpensiveToCopyType());
+}
+
+template <typename T> void instantiatedTemplateWithConstValue(const T S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:71: warning: the const qualified parameter 'S'
+ // CHECK-FIXES: template <typename T> void
instantiatedTemplateWithConstValue(const T& S) {
+}
+
+void instantiatedConstValue() {
+ instantiatedTemplateWithConstValue(ExpensiveToCopyType());
+}
+
+template <typename T> void instantiatedTemplateWithNonConstValue(T S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:68: warning: the parameter 'S'
+ // CHECK-FIXES: template <typename T> void
instantiatedTemplateWithNonConstValue(const T& S) {
+}
+
+void instantiatedNonConstValue() {
+ instantiatedTemplateWithNonConstValue(ExpensiveToCopyType());
+}
+
+void lambdaConstValue() {
+ auto fn = [](const ExpensiveToCopyType S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:42: warning: the const qualified parameter
'S'
+ // CHECK-FIXES: auto fn = [](const ExpensiveToCopyType& S) {
+ };
+ fn(ExpensiveToCopyType());
+}
+
+void lambdaNonConstValue() {
+ auto fn = [](ExpensiveToCopyType S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:36: warning: the parameter 'S'
+ // CHECK-FIXES: auto fn = [](const ExpensiveToCopyType& S) {
+ };
+ fn(ExpensiveToCopyType());
+}
+
+void lambdaConstAutoValue() {
+ auto fn = [](const auto S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:27: warning: the const qualified parameter
'S'
+ // CHECK-FIXES: auto fn = [](const auto& S) {
+ };
+ fn(ExpensiveToCopyType());
+}
+
+void lambdaNonConstAutoValue() {
+ auto fn = [](auto S) {
+ // CHECK-MESSAGES: [[@LINE-1]]:21: warning: the parameter 'S'
+ // CHECK-FIXES: auto fn = [](const auto& S) {
+ };
+ fn(ExpensiveToCopyType());
+}
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp
b/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp
index d578eedd94a39..0dffaefa213a4 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp
@@ -107,19 +107,6 @@ struct PositiveConstValueConstructor {
// CHECK-FIXES: PositiveConstValueConstructor(const ExpensiveToCopyType&
ConstCopy) {}
};
-template <typename T> void templateWithNonTemplatizedParameter(const
ExpensiveToCopyType S, T V) {
- // CHECK-MESSAGES: [[@LINE-1]]:90: warning: the const qualified parameter 'S'
- // CHECK-FIXES-NOT: template <typename T> void
templateWithNonTemplatizedParameter(const ExpensiveToCopyType& S, T V) {
-}
-
-void instantiated() {
- templateWithNonTemplatizedParameter(ExpensiveToCopyType(),
ExpensiveToCopyType());
- templateWithNonTemplatizedParameter(ExpensiveToCopyType(), 5);
-}
-
-template <typename T> void negativeTemplateType(const T V) {
-}
-
void negativeArray(const ExpensiveToCopyType[]) {
}
@@ -370,35 +357,3 @@ void fun() {
ExpensiveToCopyType E;
NegativeUsingConstructor S(E);
}
-
-template<typename T>
-void templateFunction(T) {
-}
-
-template<>
-void templateFunction<ExpensiveToCopyType>(ExpensiveToCopyType E) {
- // CHECK-MESSAGES: [[@LINE-1]]:64: warning: the parameter 'E' is copied
- // CHECK-FIXES: void
templateFunction<ExpensiveToCopyType>(ExpensiveToCopyType E) {
- E.constReference();
-}
-
-template <class T>
-T templateSpecializationFunction(ExpensiveToCopyType E) {
- // CHECK-MESSAGES: [[@LINE-1]]:54: warning: the parameter 'E' is copied
- // CHECK-FIXES-NOT: T templateSpecializationFunction(const
ExpensiveToCopyType& E) {
- return T();
-}
-
-template <>
-bool templateSpecializationFunction(ExpensiveToCopyType E) {
- // CHECK-MESSAGES: [[@LINE-1]]:57: warning: the parameter 'E' is copied
- // CHECK-FIXES-NOT: bool templateSpecializationFunction(const
ExpensiveToCopyType& E) {
- return true;
-}
-
-template <>
-int templateSpecializationFunction(ExpensiveToCopyType E) {
- // CHECK-MESSAGES: [[@LINE-1]]:56: warning: the parameter 'E' is copied
- // CHECK-FIXES-NOT: int templateSpecializationFunction(const
ExpensiveToCopyType& E) {
- return 0;
-}
``````````
</details>
https://github.com/llvm/llvm-project/pull/97767
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