Hi alexfh,
The \c shrink_to_fit() method is more readable and more effective than
the copy and swap trick to reduce the capacity of a shrinkable container.
Note that, the \c shrink_to_fit() method is only available in C++11 and up.
Example:
std::vector<int>(v).swap(v); will be replaced with v.shrink_to_fit();
There was already a checker which targeted C++11, however it did not contain
any check, which standard is used during the analysis. Maybe a check should be
added to suppress C++11 specific warnings when clang tidy is invoked in C++03
mode?
http://reviews.llvm.org/D7087
Files:
clang-tidy/readability/CMakeLists.txt
clang-tidy/readability/ReadabilityTidyModule.cpp
clang-tidy/readability/ShrinkToFitCheck.cpp
clang-tidy/readability/ShrinkToFitCheck.h
test/clang-tidy/readability-shrink-to-fit.cpp
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Index: clang-tidy/readability/CMakeLists.txt
===================================================================
--- clang-tidy/readability/CMakeLists.txt
+++ clang-tidy/readability/CMakeLists.txt
@@ -8,6 +8,7 @@
NamespaceCommentCheck.cpp
ReadabilityTidyModule.cpp
RedundantSmartptrGet.cpp
+ ShrinkToFitCheck.cpp
LINK_LIBS
clangAST
Index: clang-tidy/readability/ReadabilityTidyModule.cpp
===================================================================
--- clang-tidy/readability/ReadabilityTidyModule.cpp
+++ clang-tidy/readability/ReadabilityTidyModule.cpp
@@ -15,6 +15,7 @@
#include "ElseAfterReturnCheck.h"
#include "FunctionSize.h"
#include "RedundantSmartptrGet.h"
+#include "ShrinkToFitCheck.h"
namespace clang {
namespace tidy {
@@ -33,6 +34,8 @@
"readability-function-size");
CheckFactories.registerCheck<RedundantSmartptrGet>(
"readability-redundant-smartptr-get");
+ CheckFactories.registerCheck<ShrinkToFitCheck>(
+ "readability-shrink-to-fit");
}
};
Index: clang-tidy/readability/ShrinkToFitCheck.cpp
===================================================================
--- clang-tidy/readability/ShrinkToFitCheck.cpp
+++ clang-tidy/readability/ShrinkToFitCheck.cpp
@@ -0,0 +1,83 @@
+//===--- ShrinkToFitCheck.cpp - clang-tidy---------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ShrinkToFitCheck.h"
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSet.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace {
+bool isShrinkableContainer(llvm::StringRef ClassName) {
+ static const llvm::StringSet<> Shrinkables = [] {
+ llvm::StringSet<> RetVal;
+ RetVal.insert("std::deque");
+ RetVal.insert("std::basic_string");
+ RetVal.insert("std::vector");
+ return RetVal;
+ }();
+ return Shrinkables.find(ClassName) != Shrinkables.end();
+}
+}
+
+namespace clang {
+namespace ast_matchers {
+AST_MATCHER(NamedDecl, stlShrinkableContainer) {
+ return isShrinkableContainer(Node.getQualifiedNameAsString());
+}
+} // namespace ast_matchesr
+} // namespace clang
+
+namespace clang {
+namespace tidy {
+
+void ShrinkToFitCheck::registerMatchers(MatchFinder *Finder) {
+ // Swap as a function need not to be considered, because rvalue can not
+ // be bound to a non-const reference.
+ const auto CopyCtorCall = constructExpr(hasArgument(
+ 0, anyOf(memberExpr(member(valueDecl().bind("CtorParam"))),
+ declRefExpr(hasDeclaration(valueDecl().bind("CtorParam"))))));
+ const auto SwapParam =
+ expr(anyOf(memberExpr(member(equalsBoundNode("CtorParam"))),
+ declRefExpr(hasDeclaration(equalsBoundNode("CtorParam")))));
+
+ Finder->addMatcher(
+ memberCallExpr(on(hasType(namedDecl(stlShrinkableContainer()))),
+ callee(methodDecl(hasName("swap"))),
+ has(memberExpr(hasDescendant(CopyCtorCall))),
+ hasArgument(0, SwapParam.bind("ContainerToShrink")))
+ .bind("CopyAndSwapTrick"),
+ this);
+}
+
+void ShrinkToFitCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *MemberCall =
+ Result.Nodes.getNodeAs<CXXMemberCallExpr>("CopyAndSwapTrick");
+ const auto *ContainerToShrink =
+ Result.Nodes.getNodeAs<Expr>("ContainerToShrink");
+
+ std::string ReplacementText = Lexer::getSourceText(
+ CharSourceRange::getTokenRange(ContainerToShrink->getSourceRange()),
+ *Result.SourceManager, LangOptions());
+ ReplacementText += ".shrink_to_fit()";
+
+ diag(MemberCall->getLocStart(), "The shrink_to_fit method should be used "
+ "to reduce the capacity of a shrinkable "
+ "container")
+ << FixItHint::CreateReplacement(MemberCall->getSourceRange(),
+ ReplacementText);
+ ;
+}
+
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/readability/ShrinkToFitCheck.h
===================================================================
--- clang-tidy/readability/ShrinkToFitCheck.h
+++ clang-tidy/readability/ShrinkToFitCheck.h
@@ -0,0 +1,35 @@
+//===--- ShrinkToFitCheck.h - clang-tidy-------------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SHRINK_TO_FIT_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SHRINK_TO_FIT_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+
+/// \brief Replace copy and swap tricks on shrinkable containers with the \c
+/// shrink_to_fit() method call.
+///
+/// The \c shrink_to_fit() method is more readable and more effective than
+/// the copy and swap trick to reduce the capacity of a shrinkable container.
+/// Note that, the \c shrink_to_fit() method is only available in C++11 and up.
+class ShrinkToFitCheck : public ClangTidyCheck {
+public:
+ ShrinkToFitCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SHRINK_TO_FIT_H
Index: test/clang-tidy/readability-shrink-to-fit.cpp
===================================================================
--- test/clang-tidy/readability-shrink-to-fit.cpp
+++ test/clang-tidy/readability-shrink-to-fit.cpp
@@ -0,0 +1,49 @@
+// RUN: $(dirname %s)/check_clang_tidy.sh %s readability-shrink-to-fit %t
+// REQUIRES: shell
+
+namespace std {
+template <typename T> struct vector { void swap(vector &other); };
+}
+
+void f() {
+ std::vector<int> v;
+
+ std::vector<int>(v).swap(v);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: The shrink_to_fit method should be used to reduce the capacity of a shrinkable container [readability-shrink-to-fit]
+ // CHECK-FIXES: {{^ }}v.shrink_to_fit();{{$}}
+
+ std::vector<int>& vref = v;
+ std::vector<int>(vref).swap(vref);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: The shrink_to_fit method should
+ // CHECK-FIXES: {{^ }}vref.shrink_to_fit();{{$}}
+}
+
+struct X {
+ std::vector<int> v;
+ void f() {
+ std::vector<int>(v).swap(v);
+ // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: The shrink_to_fit method should
+ // CHECK-FIXES: {{^ }}v.shrink_to_fit();{{$}}
+ }
+};
+
+template <typename T> void g() {
+ std::vector<int> v;
+
+ std::vector<int>(v).swap(v);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: The shrink_to_fit method should
+ // CHECK-FIXES: {{^ }}v.shrink_to_fit();{{$}}
+}
+
+#define COPY_AND_SWAP_INT_VEC(x) std::vector<int>(x).swap(x)
+// CHECK-FIXES: #define COPY_AND_SWAP_INT_VEC(x) std::vector<int>(x).swap(x)
+
+void h() {
+ g<int>();
+ g<double>();
+ g<bool>();
+ std::vector<int> v;
+ COPY_AND_SWAP_INT_VEC(v);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: The shrink_to_fit method should
+}
+
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