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[clang-tidy] Added DefaultOperatorNewCheck.
Summary: Added new checker 'cert-default-operator-new' that checks for CERT rule MEM57-CPP. Simple version. Reviewers: aaron.ballman, alexfh, JonasToth, lebedev.ri Reviewed By: aaron.ballman Subscribers: hiraditya, martong, mehdi_amini, mgorny, inglorion, xazax.hun, dkrupp, steven_wu, dexonsmith, Szelethus, gamesh411, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D67545
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‎clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp

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@@ -19,6 +19,7 @@
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#include "../performance/MoveConstructorInitCheck.h"
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#include "../readability/UppercaseLiteralSuffixCheck.h"
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#include "CommandProcessorCheck.h"
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#include "DefaultOperatorNewAlignmentCheck.h"
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#include "DontModifyStdNamespaceCheck.h"
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#include "FloatLoopCounter.h"
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#include "LimitedRandomnessCheck.h"
@@ -48,11 +49,6 @@ class CERTModule : public ClangTidyModule {
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"cert-dcl58-cpp");
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CheckFactories.registerCheck<google::build::UnnamedNamespaceInHeaderCheck>(
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"cert-dcl59-cpp");
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// OOP
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CheckFactories.registerCheck<performance::MoveConstructorInitCheck>(
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"cert-oop11-cpp");
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CheckFactories.registerCheck<bugprone::UnhandledSelfAssignmentCheck>(
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"cert-oop54-cpp");
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// ERR
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CheckFactories.registerCheck<misc::ThrowByValueCatchByReferenceCheck>(
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"cert-err09-cpp");
@@ -61,10 +57,18 @@ class CERTModule : public ClangTidyModule {
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CheckFactories.registerCheck<ThrownExceptionTypeCheck>("cert-err60-cpp");
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CheckFactories.registerCheck<misc::ThrowByValueCatchByReferenceCheck>(
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"cert-err61-cpp");
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// MEM
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CheckFactories.registerCheck<DefaultOperatorNewAlignmentCheck>(
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"cert-mem57-cpp");
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// MSC
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CheckFactories.registerCheck<LimitedRandomnessCheck>("cert-msc50-cpp");
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CheckFactories.registerCheck<ProperlySeededRandomGeneratorCheck>(
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"cert-msc51-cpp");
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// OOP
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CheckFactories.registerCheck<performance::MoveConstructorInitCheck>(
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"cert-oop11-cpp");
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CheckFactories.registerCheck<bugprone::UnhandledSelfAssignmentCheck>(
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"cert-oop54-cpp");
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// C checkers
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// DCL

‎clang-tools-extra/clang-tidy/cert/CMakeLists.txt

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@@ -3,6 +3,7 @@ set(LLVM_LINK_COMPONENTS support)
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add_clang_library(clangTidyCERTModule
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CERTTidyModule.cpp
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CommandProcessorCheck.cpp
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DefaultOperatorNewAlignmentCheck.cpp
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DontModifyStdNamespaceCheck.cpp
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FloatLoopCounter.cpp
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LimitedRandomnessCheck.cpp

‎clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp

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//===--- DefaultOperatorNewCheck.cpp - clang-tidy --------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "DefaultOperatorNewAlignmentCheck.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/ASTMatchers/ASTMatchFinder.h"
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using namespace clang::ast_matchers;
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namespace clang {
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namespace tidy {
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namespace cert {
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AST_MATCHER(CXXNewExpr, isPlacementNew) {
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return Node.getNumPlacementArgs() > 0;
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}
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void DefaultOperatorNewAlignmentCheck::registerMatchers(MatchFinder *Finder) {
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// Check not applicable in C++17 (or newer).
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if (getLangOpts().CPlusPlus17)
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return;
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Finder->addMatcher(cxxNewExpr(unless(isPlacementNew())).bind("new"), this);
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}
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void DefaultOperatorNewAlignmentCheck::check(
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const MatchFinder::MatchResult &Result) {
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// Get the found 'new' expression.
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const auto *NewExpr = Result.Nodes.getNodeAs<CXXNewExpr>("new");
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QualType T = NewExpr->getAllocatedType();
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// Dependent types do not have fixed alignment.
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if (T->isDependentType())
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return;
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const TagDecl *D = T->getAsTagDecl();
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// Alignment can not be obtained for undefined type.
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if (!D || !D->getDefinition() || !D->isCompleteDefinition())
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return;
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ASTContext &Context = D->getASTContext();
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// Check if no alignment was specified for the type.
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if (!Context.isAlignmentRequired(T))
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return;
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// The user-specified alignment (in bits).
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unsigned SpecifiedAlignment = D->getMaxAlignment();
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// Double-check if no alignment was specified.
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if (!SpecifiedAlignment)
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return;
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// The alignment used by default 'operator new' (in bits).
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unsigned DefaultNewAlignment = Context.getTargetInfo().getNewAlign();
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bool OverAligned = SpecifiedAlignment > DefaultNewAlignment;
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bool HasDefaultOperatorNew =
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!NewExpr->getOperatorNew() || NewExpr->getOperatorNew()->isImplicit();
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unsigned CharWidth = Context.getTargetInfo().getCharWidth();
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if (HasDefaultOperatorNew && OverAligned)
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diag(NewExpr->getBeginLoc(),
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"allocation function returns a pointer with alignment %0 but the "
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"over-aligned type being allocated requires alignment %1")
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<< (DefaultNewAlignment / CharWidth)
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<< (SpecifiedAlignment / CharWidth);
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}
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} // namespace cert
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} // namespace tidy
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} // namespace clang

‎clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.h

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//===--- DefaultOperatorNewCheck.h - clang-tidy -----------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DEFAULTOPERATORNEWALIGNMENTCHECK_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DEFAULTOPERATORNEWALIGNMENTCHECK_H
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#include "../ClangTidyCheck.h"
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namespace clang {
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namespace tidy {
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namespace cert {
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/// Checks if an object of type with extended alignment is allocated by using
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/// the default operator new.
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///
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/// For the user-facing documentation see:
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/// http://clang.llvm.org/extra/clang-tidy/checks/cert-mem57-cpp.html
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class DefaultOperatorNewAlignmentCheck : public ClangTidyCheck {
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public:
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DefaultOperatorNewAlignmentCheck(StringRef Name, ClangTidyContext *Context)
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: ClangTidyCheck(Name, Context) {}
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void registerMatchers(ast_matchers::MatchFinder *Finder) override;
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void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
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};
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} // namespace cert
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} // namespace tidy
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} // namespace clang
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DEFAULTOPERATORNEWALIGNMENTCHECK_H

‎clang-tools-extra/docs/ReleaseNotes.rst

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Without the null terminator it can result in undefined behaviour when the
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string is read.
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- New :doc:`cert-mem57-cpp
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<clang-tidy/checks/cert-mem57-cpp>` check.
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Checks if an object of type with extended alignment is allocated by using
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the default ``operator new``.
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- New alias :doc:`cert-pos44-c
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<clang-tidy/checks/cert-pos44-c>` to
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:doc:`bugprone-bad-signal-to-kill-thread

‎clang-tools-extra/docs/clang-tidy/checks/cert-mem57-cpp.rst

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.. title:: clang-tidy - cert-mem57-cpp
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cert-mem57-cpp
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==============
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This check flags uses of default ``operator new`` where the type has extended
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alignment (an alignment greater than the fundamental alignment). (The default
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``operator new`` is guaranteed to provide the correct alignmment if the
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requested alignment is less or equal to the fundamental alignment).
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Only cases are detected (by design) where the ``operator new`` is not
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user-defined and is not a placement new (the reason is that in these cases we
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assume that the user provided the correct memory allocation).
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This check corresponds to the CERT C++ Coding Standard rule
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`MEM57-CPP. Avoid using default operator new for over-aligned types
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<https://wiki.sei.cmu.edu/confluence/display/cplusplus/MEM57-CPP.+Avoid+using+default+operator+new+for+over-aligned+types>`_.

‎clang-tools-extra/docs/clang-tidy/checks/list.rst

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@@ -100,6 +100,7 @@ Clang-Tidy Checks
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cert-err61-cpp (redirects to misc-throw-by-value-catch-by-reference) <cert-err61-cpp>
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cert-fio38-c (redirects to misc-non-copyable-objects) <cert-fio38-c>
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cert-flp30-c
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cert-mem57-cpp
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cert-msc30-c (redirects to cert-msc50-cpp) <cert-msc30-c>
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cert-msc32-c (redirects to cert-msc51-cpp) <cert-msc32-c>
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cert-msc50-cpp

‎clang-tools-extra/test/clang-tidy/cert-mem57-cpp-cpp17.cpp

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// RUN: %check_clang_tidy %s -std=c++14 cert-mem57-cpp %t
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// RUN: clang-tidy --extra-arg='-std=c++17' -checks='-*,cert-mem57-cpp' --warnings-as-errors='*' %s
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// RUN: clang-tidy --extra-arg='-std=c++2a' -checks='-*,cert-mem57-cpp' --warnings-as-errors='*' %s
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struct alignas(32) Vector {
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char Elems[32];
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};
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void f() {
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auto *V1 = new Vector; // CHECK-MESSAGES: warning: allocation function returns a pointer with alignment 16 but the over-aligned type being allocated requires alignment 32 [cert-mem57-cpp]
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auto *V1_Arr = new Vector[2]; // CHECK-MESSAGES: warning: allocation function returns a pointer with alignment 16 but the over-aligned type being allocated requires alignment 32 [cert-mem57-cpp]
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}

‎clang-tools-extra/test/clang-tidy/cert-mem57-cpp.cpp

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// RUN: %check_clang_tidy %s -std=c++14 cert-mem57-cpp %t
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namespace std {
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typedef __typeof(sizeof(int)) size_t;
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void *aligned_alloc(size_t, size_t);
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void free(void *);
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} // namespace std
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struct alignas(32) Vector1 {
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char elems[32];
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};
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struct Vector2 {
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char elems[32];
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};
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struct alignas(32) Vector3 {
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char elems[32];
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static void *operator new(std::size_t nbytes) noexcept(true) {
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return std::aligned_alloc(alignof(Vector3), nbytes);
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}
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static void operator delete(void *p) {
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std::free(p);
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}
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};
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struct alignas(8) Vector4 {
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char elems[32];
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};
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void f() {
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auto *V1 = new Vector1;
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// CHECK-MESSAGES: :[[@LINE-1]]:14: warning: allocation function returns a pointer with alignment 16 but the over-aligned type being allocated requires alignment 32 [cert-mem57-cpp]
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auto *V2 = new Vector2;
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auto *V3 = new Vector3;
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auto *V4 = new Vector4;
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auto *V1_Arr = new Vector1[2];
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// CHECK-MESSAGES: :[[@LINE-1]]:18: warning: allocation function returns a pointer with alignment 16 but the over-aligned type being allocated requires alignment 32 [cert-mem57-cpp]
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}

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