AMS21 updated this revision to Diff 513582.
AMS21 added a comment.
Rename to `performance-avoid-endl`
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D148318/new/
https://reviews.llvm.org/D148318
Files:
clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.cpp
clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.h
clang-tools-extra/clang-tidy/performance/CMakeLists.txt
clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
clang-tools-extra/docs/ReleaseNotes.rst
clang-tools-extra/docs/clang-tidy/checks/list.rst
clang-tools-extra/docs/clang-tidy/checks/performance/avoid-endl.rst
clang-tools-extra/test/clang-tidy/checkers/performance/avoid-endl.cpp
Index: clang-tools-extra/test/clang-tidy/checkers/performance/avoid-endl.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/performance/avoid-endl.cpp
@@ -0,0 +1,71 @@
+// RUN: %check_clang_tidy %s performance-avoid-endl %t
+
+namespace std
+{
+ template <typename CharT>
+ class basic_ostream {
+ public:
+ template <typename T>
+ basic_ostream& operator<<(T) {
+ return *this;
+ }
+
+ basic_ostream& operator<<( basic_ostream<CharT>& (*func)
+ (basic_ostream<CharT>&))
+ {
+ return func(*this);
+ }
+ };
+
+ template <typename CharT>
+ class basic_iostream : public basic_ostream<CharT> {
+ };
+
+ using ostream = basic_ostream<char>;
+ using iostream = basic_iostream<char>;
+
+ iostream cout;
+ iostream cerr;
+
+ template<typename CharT>
+ basic_ostream<CharT>& endl(basic_ostream<CharT>& os)
+ {
+ return os;
+ }
+} // namespace std
+
+void good() {
+ std::cout << "Hello" << '\n';
+ std::cout << "World\n";
+
+ std::cerr << "Hello" << '\n';
+ std::cerr << "World\n";
+}
+
+void bad() {
+ std::cout << "World" << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not use std::endl with iostreams; use '\n' instead
+ std::cerr << "World" << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not use std::endl with iostreams; use '\n' instead
+}
+
+void bad_single_argument() {
+ std::cout << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use std::endl with iostreams; use '\n' instead
+ std::cerr << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use std::endl with iostreams; use '\n' instead
+}
+
+void bad_multiple() {
+ std::cout << "Hello" << std::endl << "World" << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not use std::endl with iostreams; use '\n' instead
+ std::cerr << "Hello" << std::endl << "World" << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not use std::endl with iostreams; use '\n' instead
+}
+
+void bad_user_stream() {
+ std::iostream my_stream;
+
+ my_stream << "Hi" << std::endl;
+ // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: do not use std::endl with iostreams; use '\n' instead
+}
Index: clang-tools-extra/docs/clang-tidy/checks/performance/avoid-endl.rst
===================================================================
--- /dev/null
+++ clang-tools-extra/docs/clang-tidy/checks/performance/avoid-endl.rst
@@ -0,0 +1,34 @@
+.. title:: clang-tidy - performance-avoid-endl
+
+performance-avoid-endl
+======================
+
+Checks for uses of ``std::endl`` on iostreams and suggests using the newline character ``'\n'`` instead.
+
+Rationale:
+Using ``std::endl`` on iostreams can be less efficient than using the newline character ``'\n'`` because ``std::endl`` performs two operations: it writes a newline character to the output stream and then flushes the stream buffer. Writing a single newline character using ``'\n'`` does not trigger a flush, which can improve performance. In addition, flushing the stream buffer can cause additional overhead when working with streams that are buffered.
+
+Example:
+
+Consider the following code:
+
+.. code-block:: c++
+
+ #include <iostream>
+
+ int main() {
+ std::cout << "Hello" << std::endl;
+ }
+
+The ``std::endl`` on line 4 performs two operations: it writes a newline character to the ``std::cout`` stream and then flushes the stream buffer. This can be less efficient than using the newline character ``'\n'`` instead:
+
+.. code-block:: c++
+ #include <iostream>
+
+ int main() {
+ std::cout << "Hello" << '\n';
+ }
+
+This code writes a single newline character to the ``std::cout`` stream without flushing the stream buffer.
+
+If you do need to flush the stream buffer explicitly, you can just use ``std::flush``.
Index: clang-tools-extra/docs/clang-tidy/checks/list.rst
===================================================================
--- clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -313,6 +313,7 @@
`objc-super-self <objc/super-self.html>`_, "Yes"
`openmp-exception-escape <openmp/exception-escape.html>`_,
`openmp-use-default-none <openmp/use-default-none.html>`_,
+ `performance-avoid-endl <performance/avoid-endl.html>`_, "Yes"
`performance-faster-string-find <performance/faster-string-find.html>`_, "Yes"
`performance-for-range-copy <performance/for-range-copy.html>`_, "Yes"
`performance-implicit-conversion-in-loop <performance/implicit-conversion-in-loop.html>`_,
Index: clang-tools-extra/docs/ReleaseNotes.rst
===================================================================
--- clang-tools-extra/docs/ReleaseNotes.rst
+++ clang-tools-extra/docs/ReleaseNotes.rst
@@ -142,6 +142,11 @@
Converts standard library type traits of the form ``traits<...>::type`` and
``traits<...>::value`` into ``traits_t<...>`` and ``traits_v<...>`` respectively.
+- New :doc:`performance-avoid-endl
+ <clang-tidy/checks/performance/avoid-endl>` check.
+
+ Finds uses of ``std::endl`` on streams and replaces them with ``'\n'``.
+
- New :doc:`readability-avoid-unconditional-preprocessor-if
<clang-tidy/checks/readability/avoid-unconditional-preprocessor-if>` check.
Index: clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
===================================================================
--- clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
+++ clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
@@ -9,6 +9,7 @@
#include "../ClangTidy.h"
#include "../ClangTidyModule.h"
#include "../ClangTidyModuleRegistry.h"
+#include "AvoidEndlCheck.h"
#include "FasterStringFindCheck.h"
#include "ForRangeCopyCheck.h"
#include "ImplicitConversionInLoopCheck.h"
@@ -31,6 +32,7 @@
class PerformanceModule : public ClangTidyModule {
public:
void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+ CheckFactories.registerCheck<AvoidEndlCheck>("performance-avoid-endl");
CheckFactories.registerCheck<FasterStringFindCheck>(
"performance-faster-string-find");
CheckFactories.registerCheck<ForRangeCopyCheck>(
Index: clang-tools-extra/clang-tidy/performance/CMakeLists.txt
===================================================================
--- clang-tools-extra/clang-tidy/performance/CMakeLists.txt
+++ clang-tools-extra/clang-tidy/performance/CMakeLists.txt
@@ -4,6 +4,7 @@
)
add_clang_library(clangTidyPerformanceModule
+ AvoidEndlCheck.cpp
FasterStringFindCheck.cpp
ForRangeCopyCheck.cpp
ImplicitConversionInLoopCheck.cpp
Index: clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.h
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.h
@@ -0,0 +1,35 @@
+//===--- AvoidEndlCheck.h - clang-tidy --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_AVOIDENDLCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_AVOIDENDLCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::performance {
+
+/// ClangTidyCheck to flag all uses of std::endl on iostreams.
+///
+/// For the user-facing documentation see:
+/// https://clang.llvm.org/extra/clang-tidy/checks/performance/avoid-endl.html
+class AvoidEndlCheck : public ClangTidyCheck {
+public:
+ AvoidEndlCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+
+ bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+ return LangOpts.CPlusPlus;
+ }
+
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace clang::tidy::performance
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_AVOIDENDLCHECK_H
Index: clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/performance/AvoidEndlCheck.cpp
@@ -0,0 +1,47 @@
+//===--- AvoidEndlCheck.cpp - clang-tidy --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AvoidEndlCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+void AvoidEndlCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(
+ findAll(cxxOperatorCallExpr(
+ hasOverloadedOperatorName("<<"),
+ callee(cxxMethodDecl(ofClass(
+ hasAnyName("::std::basic_ostream", "::std::basic_iostream")))),
+ hasDescendant(
+ expr(declRefExpr(to(functionDecl(hasName("::std::endl"))))
+ .bind("endl"))))),
+ this);
+}
+
+void AvoidEndlCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *EndlCall = Result.Nodes.getNodeAs<DeclRefExpr>("endl");
+
+ if (!EndlCall)
+ return;
+
+ auto Diag = diag(EndlCall->getBeginLoc(),
+ "do not use std::endl with iostreams; use '\\n' instead");
+
+ // Add a fix-it hint to replace std::endl with '\n'
+ Diag << FixItHint::CreateReplacement(
+ CharSourceRange::getCharRange(EndlCall->getSourceRange()), "'\\n'");
+}
+
+} // namespace clang::tidy::performance
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