[clang-tools-extra] [clang-tidy] fix false negative in cppcoreguidelines-missing-std-forward (PR #83987)
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Tue Mar 5 02:07:08 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-tools-extra
Author: Qizhi Hu (jcsxky)
<details>
<summary>Changes</summary>
Try to fix https://github.com/llvm/llvm-project/issues/83845
When `std::forward` is invoked in a function, make sure it uses correct parameter by checking if the bounded `var` equals the parameter.
---
Full diff: https://github.com/llvm/llvm-project/pull/83987.diff
3 Files Affected:
- (modified) clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp (+6-4)
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+2-1)
- (modified) clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp (+10)
``````````diff
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
index c633683570f748..87fd8adf997082 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
@@ -112,10 +112,12 @@ void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
auto ForwardCallMatcher = callExpr(
callExpr().bind("call"), argumentCountIs(1),
- hasArgument(
- 0, declRefExpr(to(
- varDecl(optionally(equalsBoundNode("param"))).bind("var")))),
- forCallable(anyOf(equalsBoundNode("func"), CapturedInLambda)),
+ hasArgument(0, declRefExpr(to(varDecl().bind("var")))),
+ forCallable(
+ anyOf(allOf(equalsBoundNode("func"),
+ functionDecl(hasAnyParameter(parmVarDecl(allOf(
+ equalsBoundNode("param"), equalsBoundNode("var")))))),
+ CapturedInLambda)),
callee(unresolvedLookupExpr(hasAnyDeclaration(
namedDecl(hasUnderlyingDecl(hasName("::std::forward")))))),
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 143ae230fc443c..1abe45bae8a84d 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -156,7 +156,8 @@ Changes in existing checks
- Improved :doc:`cppcoreguidelines-missing-std-forward
<clang-tidy/checks/cppcoreguidelines/missing-std-forward>` check by no longer
- giving false positives for deleted functions.
+ giving false positives for deleted functions and fix false negative when one
+ parameter is forwarded, but some other parameter isn't.
- Cleaned up :doc:`cppcoreguidelines-prefer-member-initializer
<clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>`
diff --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
index 20e43f04180ff3..29af67b60614c8 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
@@ -95,6 +95,16 @@ void lambda_value_capture_copy(T&& t) {
[&,t]() { T other = std::forward<T>(t); };
}
+template <typename X>
+void use(const X &x) {}
+
+template <typename X, typename Y>
+void foo(X &&x, Y &&y) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: forwarding reference parameter 't' is never forwarded inside the function body [cppcoreguidelines-missing-std-forward]
+ use(std::forward<X>(x));
+ use(y);
+}
+
} // namespace positive_cases
namespace negative_cases {
``````````
</details>
https://github.com/llvm/llvm-project/pull/83987
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