[clang] 92023b1 - Reland "[Clang][SemaCXX] Add unused warning for variables declared in condition expressions"
Takuya Shimizu via cfe-commits
cfe-commits at lists.llvm.org
Tue Aug 29 18:07:09 PDT 2023
Author: Takuya Shimizu
Date: 2023-08-30T10:05:10+09:00
New Revision: 92023b15099012a657da07ebf49dd7d94a260f84
URL: https://github.com/llvm/llvm-project/commit/92023b15099012a657da07ebf49dd7d94a260f84
DIFF: https://github.com/llvm/llvm-project/commit/92023b15099012a657da07ebf49dd7d94a260f84.diff
LOG: Reland "[Clang][SemaCXX] Add unused warning for variables declared in condition expressions"
This patch marks the declarations with initializations in condition expressions such as
if (int var = init) as unused and unreferenced so that -Wunused can warn on them.
Fixes https://github.com/llvm/llvm-project/issues/61681
Reviewed By: cor3ntin
Differential Revision: https://reviews.llvm.org/D152495
Added:
Modified:
clang/docs/ReleaseNotes.rst
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaExprCXX.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/SemaCXX/warn-unused-variables.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index dc7569cf79f43e..262bebfc0bde9b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -156,6 +156,9 @@ Improvements to Clang's diagnostics
(`#64871: <https://github.com/llvm/llvm-project/issues/64871>`_).
Also clang no longer emits false positive warnings about the output length of
``%g`` format specifier.
+- Clang now warns on unused variables declared and initialized in condition
+ expressions.
+ (`#61681: <https://github.com/llvm/llvm-project/issues/61681>`_)
Bug Fixes in This Version
-------------------------
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 2ee216fffaa275..9facf2187f76a5 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1995,7 +1995,7 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions &LangOpts,
return false;
} else if (!D->getDeclName()) {
return false;
- } else if (D->isReferenced() || D->isUsed()) {
+ } else if (D->isReferenced() || (!isa<VarDecl>(D) && D->isUsed())) {
return false;
}
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index a6e0a8abf81b9a..a9096af70fce4e 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -4013,6 +4013,10 @@ ExprResult Sema::CheckConditionVariable(VarDecl *ConditionVar,
ConditionVar, ConditionVar->getType().getNonReferenceType(), VK_LValue,
ConditionVar->getLocation());
+ // Ensure that `-Wunused-variable` will be emitted for condition variables
+ // that are not referenced later. e.g.: if (int var = init());
+ ConditionVar->setReferenced(/*R=*/false);
+
switch (CK) {
case ConditionKind::Boolean:
return CheckBooleanCondition(StmtLoc, Condition.get());
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 63f022d5c2ff09..bb8ea187ecf91c 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -5353,7 +5353,7 @@ void Sema::BuildVariableInstantiation(
// will have been deferred.
if (!NewVar->isInvalidDecl() &&
NewVar->getDeclContext()->isFunctionOrMethod() &&
- OldVar->getType()->isDependentType())
+ OldVar->getType()->isDependentType() && !OldVar->isImplicit())
DiagnoseUnusedDecl(NewVar);
}
diff --git a/clang/test/SemaCXX/warn-unused-variables.cpp b/clang/test/SemaCXX/warn-unused-variables.cpp
index 4db8bdf12e5de0..db33086436d3af 100644
--- a/clang/test/SemaCXX/warn-unused-variables.cpp
+++ b/clang/test/SemaCXX/warn-unused-variables.cpp
@@ -1,5 +1,5 @@
// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Wunused-label -Wno-c++1y-extensions -verify %s
-// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Wunused-label -Wno-c++1y-extensions -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Wunused-label -Wno-c++14-extensions -Wno-c++17-extensions -verify -std=c++11 %s
template<typename T> void f() {
T t;
t = 17;
@@ -294,3 +294,115 @@ void RAIIWrapperTest() {
}
} // namespace gh54489
+
+namespace inside_condition {
+ void ifs() {
+ if (int hoge = 0) // expected-warning {{unused variable 'hoge'}}
+ return;
+ if (const int const_hoge = 0) // expected-warning {{unused variable 'const_hoge'}}
+ return;
+ else if (int fuga = 0)
+ (void)fuga;
+ else if (int used = 1; int catched = used) // expected-warning {{unused variable 'catched'}}
+ return;
+ else if (int refed = 1; int used = refed)
+ (void)used;
+ else if (int unused1 = 2; int unused2 = 3) // expected-warning {{unused variable 'unused1'}} \
+ // expected-warning {{unused variable 'unused2'}}
+ return;
+ else if (int unused = 4; int used = 5) // expected-warning {{unused variable 'unused'}}
+ (void)used;
+ else if (int used = 6; int unused = 7) // expected-warning {{unused variable 'unused'}}
+ (void)used;
+ else if (int used1 = 8; int used2 = 9)
+ (void)(used1 + used2);
+ else if (auto [a, b] = (int[2]){ 1, 2 }; 1) // expected-warning {{unused variable '[a, b]'}}
+ return;
+ else if (auto [a, b] = (int[2]){ 1, 2 }; a)
+ return;
+ }
+
+ void fors() {
+ for (int i = 0;int unused = 0;); // expected-warning {{unused variable 'i'}} \
+ // expected-warning {{unused variable 'unused'}}
+ for (int i = 0;int used = 0;) // expected-warning {{unused variable 'i'}}
+ (void)used;
+ while(int var = 1) // expected-warning {{unused variable 'var'}}
+ return;
+ }
+
+ void whiles() {
+ while(int unused = 1) // expected-warning {{unused variable 'unused'}}
+ return;
+ while(int used = 1)
+ (void)used;
+ }
+
+
+ void switches() {
+ switch(int unused = 1) { // expected-warning {{unused variable 'unused'}}
+ case 1: return;
+ }
+ switch(constexpr int used = 3; int unused = 4) { // expected-warning {{unused variable 'unused'}}
+ case used: return;
+ }
+ switch(int used = 3; int unused = 4) { // expected-warning {{unused variable 'unused'}}
+ case 3: (void)used;
+ }
+ switch(constexpr int used1 = 0; constexpr int used2 = 6) {
+ case (used1+used2): return;
+ }
+ switch(auto [a, b] = (int[2]){ 1, 2 }; 1) { // expected-warning {{unused variable '[a, b]'}}
+ case 1: return;
+ }
+ switch(auto [a, b] = (int[2]){ 1, 2 }; b) {
+ case 1: return;
+ }
+ switch(auto [a, b] = (int[2]){ 1, 2 }; 1) {
+ case 1: (void)a;
+ }
+ }
+ template <typename T>
+ struct Vector {
+ void doIt() {
+ for (auto& e : elements){} // expected-warning {{unused variable 'e'}}
+ }
+ T elements[10];
+ };
+ void ranged_for() {
+ Vector<int> vector;
+ vector.doIt(); // expected-note {{here}}
+ }
+
+
+ struct RAII {
+ int &x;
+ RAII(int &ref) : x(ref) {}
+ ~RAII() { x = 0;}
+ operator int() const { return 1; }
+ };
+ void aggregate() {
+ int x = 10;
+ int y = 10;
+ if (RAII var = x) {}
+ for(RAII var = x; RAII var2 = y;) {}
+ while (RAII var = x) {}
+ switch (RAII var = x) {}
+ }
+
+ struct TrivialDtor{
+ int &x;
+ TrivialDtor(int &ref) : x(ref) { ref = 32; }
+ operator int() const { return 1; }
+ };
+ void trivial_dtor() {
+ int x = 10;
+ int y = 10;
+ if (TrivialDtor var = x) {} // expected-warning {{unused variable 'var'}}
+ for(TrivialDtor var = x; TrivialDtor var2 = y;) {} // expected-warning {{unused variable 'var'}} \
+ // expected-warning {{unused variable 'var2'}}
+ while (TrivialDtor var = x) {} // expected-warning {{unused variable 'var'}}
+ switch (TrivialDtor var = x) {} // expected-warning {{unused variable 'var'}}
+ }
+
+} // namespace inside_condition
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