https://github.com/serge-sans-paille created
https://github.com/llvm/llvm-project/pull/191435
In the following case:
template <typename T, typename U>
void shocase(U&& SomeU) {
[SomeU] () { T SomeT(std::move(SomeU)); };
}
We use to flag the move as a forward, while the lambda captures SomeU by copy,
which makes the move valid.
>From 9acd0c37d2b5887d71866707bba892126acc9efa Mon Sep 17 00:00:00 2001
From: serge-sans-paille <[email protected]>
Date: Fri, 10 Apr 2026 16:43:46 +0200
Subject: [PATCH] [clang-tidy] Fix some false positive in
bugprone-move-forwarding-reference
In the following case:
template <typename T, typename U>
void shocase(U&& SomeU) {
[SomeU] () { T SomeT(std::move(SomeU)); };
}
We use to flag the move as a forward, while the lambda captures SomeU by
copy, which makes the move valid.
---
.../bugprone/MoveForwardingReferenceCheck.cpp | 12 +++++++++-
clang-tools-extra/docs/ReleaseNotes.rst | 4 ++++
.../bugprone/move-forwarding-reference.cpp | 22 +++++++++++++++++++
3 files changed, 37 insertions(+), 1 deletion(-)
diff --git
a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
index e182df75b1d9a..7cc3d33da1a78 100644
--- a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
@@ -13,6 +13,14 @@ using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {
+namespace {
+
+AST_MATCHER(DeclRefExpr, refersToEnclosingVariableOrCapture) {
+ return Node.refersToEnclosingVariableOrCapture();
+}
+
+}
+
static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee,
const ParmVarDecl *ParmVar,
const TemplateTypeParmDecl *TypeParmDecl,
@@ -86,7 +94,9 @@ void
MoveForwardingReferenceCheck::registerMatchers(MatchFinder *Finder) {
.bind("lookup")),
argumentCountIs(1),
hasArgument(0, ignoringParenImpCasts(declRefExpr(
- to(ForwardingReferenceParmMatcher)))))
+ to(ForwardingReferenceParmMatcher),
+ // FIXME: allow capture by reference
+
unless(refersToEnclosingVariableOrCapture())))))
.bind("call-move"),
this);
}
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index caf0275035064..8a2dbfca8384b 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -256,6 +256,10 @@ Changes in existing checks
<clang-tidy/checks/bugprone/macro-parentheses>` check by printing the macro
definition in the warning message if the macro is defined on command line.
+- Improved :doc:`bugprone-move-forwarding-reference
+ <clang-tidy/checks/bugprone/move-forwarding-reference>` check by removing
some
+ false positive in the context of moved lambda captures.
+
- Improved :doc:`bugprone-pointer-arithmetic-on-polymorphic-object
<clang-tidy/checks/bugprone/pointer-arithmetic-on-polymorphic-object>` check
by fixing a false positive when ``operator[]`` is used in a dependent
context.
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/move-forwarding-reference.cpp
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/move-forwarding-reference.cpp
index c9f40668f449a..f100d6f1d3f3d 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/move-forwarding-reference.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/move-forwarding-reference.cpp
@@ -111,3 +111,25 @@ template <typename T> void f12() {
// CHECK-MESSAGES: :[[@LINE-1]]:27: warning: forwarding reference passed to
// CHECK-FIXES: [] (auto&& x) { T SomeT(std::forward<decltype(x)>(x)); };
}
+
+// Ignore the case of captured variables where an implicit copy already
+// happened. Explicit capture version.
+template <typename T, typename U> void f13(U&& SomeU) {
+ [SomeU] () { T SomeT(std::move(SomeU)); };
+}
+
+// Ignore the case of captured variables where an implicit copy already
+// happened. Implicit capture version.
+template <typename T, typename U> void f14(U&& SomeU) {
+ [=] () { T SomeT(std::move(SomeU)); };
+}
+
+#if 0
+// FIXME: we currently ignore that case.
+//
+// Handle the case of captured variables where no copy already
+// happened.
+template <typename T, typename U> void f15(U&& SomeU) {
+ [&SomeU] () { T SomeT(std::move(SomeU)); };
+}
+#endif
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