[clang-tidy] ObjC ARC objects should not trigger performance-unnecessary-value-param
Summary:
The following Objective-C code currently incorrectly triggers
clang-tidy's performance-unnecessary-value-param check:
```
% cat /tmp/performance-unnecessary-value-param-arc.m
void foo(id object) { }
clang-tidy /tmp/performance-unnecessary-value-param-arc.m
-checks=-\*,performance-unnecessary-value-param -- -xobjective-c
-fobjc-abi-version=2 -fobjc-arc
1 warning generated.
/src/llvm/tools/clang/tools/extra/test/clang-tidy/performance-unnecessary-value-param-arc.m:10:13:
warning: the parameter 'object' is copied for each invocation but only
used as a const reference; consider making it a const reference
[performance-unnecessary-value-param]
void foo(id object) { }
~~ ^
const &
```
This is wrong for a few reasons:
1) Objective-C doesn't have references, so `const &` is not going to help
2) ARC heavily optimizes the "expensive" copy which triggers the warning
This fixes the issue by disabling the warning for non-C++, as well as
disabling it for objects under ARC memory management for
Objective-C++.
Fixes https://bugs.llvm.org/show_bug.cgi?id=32075
Test Plan: New tests added. Ran tests with `make -j12 check-clang-tools`.
Reviewers: alexfh, hokein
Reviewed By: hokein
Subscribers: stephanemoore, klimek, xazax.hun, cfe-commits, Wizard
Differential Revision: https://reviews.llvm.org/D42812
llvm-svn: 324097
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
index 0dc47d5..e277ad3 100644
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
@@ -79,6 +79,10 @@
Options.getLocalOrGlobal("IncludeStyle", "llvm"))) {}
void UnnecessaryValueParamCheck::registerMatchers(MatchFinder *Finder) {
+ // This check is specific to C++ and doesn't apply to languages like
+ // Objective-C.
+ if (!getLangOpts().CPlusPlus)
+ return;
const auto ExpensiveValueParamDecl =
parmVarDecl(hasType(hasCanonicalType(allOf(
unless(referenceType()), matchers::isExpensiveToCopy()))),