https://github.com/5chmidti updated
https://github.com/llvm/llvm-project/pull/78320
>From 1951630fd6a0edc5258f5a775c95b9e9c30106df Mon Sep 17 00:00:00 2001
From: Julian Schmidt <44101708+5chmi...@users.noreply.github.com>
Date: Sat, 28 Oct 2023 18:39:18 +0200
Subject: [PATCH] [clang-tidy] fix misc-const-correctnes false-positive for
fold expressions
The check no longer emits a diagnostic for variables used as the
initializer of C++17 fold expressions.
The operator used is type-dependent because of the parameter pack
and can therefore not be guaranteed to not mutate the variable.
Fixes: #70323
---
clang-tools-extra/docs/ReleaseNotes.rst | 5 +++--
.../misc/const-correctness-templates.cpp | 17 +++++++++++++++++
clang/lib/Analysis/ExprMutationAnalyzer.cpp | 4 ++++
.../Analysis/ExprMutationAnalyzerTest.cpp | 15 +++++++++++++++
4 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index d77267588db9158..95e259873eb3c5a 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -382,7 +382,8 @@ Changes in existing checks
using pointer to member function. Additionally, the check no longer emits
a diagnostic when a variable that is not type-dependent is an operand of a
type-dependent binary operator. Improved performance of the check through
- optimizations.
+ optimizations. The check no longer emits a diagnostic for
+ variables used as the initializer of C++17 fold expressions.
- Improved :doc:`misc-include-cleaner
<clang-tidy/checks/misc/include-cleaner>` check by adding option
@@ -502,7 +503,7 @@ Changes in existing checks
<clang-tidy/checks/readability/implicit-bool-conversion>` check to take
do-while loops into account for the `AllowIntegerConditions` and
`AllowPointerConditions` options. It also now provides more consistent
- suggestions when parentheses are added to the return value or expressions.
+ suggestions when parentheses are added to the return value or expressions.
It also ignores false-positives for comparison containing bool bitfield.
- Improved :doc:`readability-misleading-indentation
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-templates.cpp
b/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-templates.cpp
index 794578ceeeba8fc..a4be41d20eae131 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-templates.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-templates.cpp
@@ -30,3 +30,20 @@ namespace gh57297{
struct Stream { };
template <typename T> void f() { T t; Stream x; x << t; }
} // namespace gh57297
+
+namespace gh70323{
+// A fold expression may contain the checked variable as it's initializer.
+// We don't know if the operator modifies that variable because the
+// operator is type dependent due to the parameter pack.
+
+struct Stream {};
+template <typename T>
+Stream& operator<<(Stream&, T);
+template <typename... Args>
+void concatenate(Args... args)
+{
+ Stream stream;
+ (stream << ... << args);
+ (args << ... << stream);
+}
+} // namespace gh70323
diff --git a/clang/lib/Analysis/ExprMutationAnalyzer.cpp
b/clang/lib/Analysis/ExprMutationAnalyzer.cpp
index 9af818be0415f39..bb042760d297a78 100644
--- a/clang/lib/Analysis/ExprMutationAnalyzer.cpp
+++ b/clang/lib/Analysis/ExprMutationAnalyzer.cpp
@@ -343,6 +343,10 @@ const Stmt *ExprMutationAnalyzer::findDirectMutation(const
Expr *Exp) {
// in different instantiations of the template.
binaryOperator(isTypeDependent(),
hasEitherOperand(ignoringImpCasts(canResolveToExpr(Exp)))),
+ // A fold expression may contain `Exp` as it's initializer.
+ // We don't know if the operator modifies `Exp` because the
+ // operator is type dependent due to the parameter pack.
+ cxxFoldExpr(hasFoldInit(ignoringImpCasts(canResolveToExpr(Exp)))),
// Within class templates and member functions the member expression
might
// not be resolved. In that case, the `callExpr` is considered to be a
// modification.
diff --git a/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
b/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
index a94f857720b0357..50d0399ed4b0159 100644
--- a/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
+++ b/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
@@ -359,6 +359,21 @@ TEST(ExprMutationAnalyzerTest,
DependentOperatorWithNonDependentOperand) {
EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x << t"));
}
+TEST(ExprMutationAnalyzerTest, FoldExpression) {
+ // gh70323
+ // A fold expression may contain `Exp` as it's initializer.
+ // We don't know if the operator modifies `Exp` because the
+ // operator is type dependent due to the parameter pack.
+ const auto AST = buildASTFromCode(
+ "struct Stream {};"
+ "template <typename T> Stream& operator<<(Stream&, T); "
+ "template <typename... Args> void concatenate(Args... args) "
+ "{ Stream x; (x << ... << args); }");
+ const auto Results =
+ match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+ EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("(x << ... <<
args)"));
+}
+
// Section: expression as call argument
TEST(ExprMutationAnalyzerTest, ByValueArgument) {
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