forked from OSchip/llvm-project
clang-tidy: introduce readability-containter-data-pointer check
This introduces a new check, readability-containter-data-pointer. This
check is meant to catch the cases where the user may be trying to
materialize the data pointer by taking the address of the 0-th member of
a container. With C++11 or newer, the `data` member should be used for
this. This provides the following benefits:
- `.data()` is easier to read than `&[0]`
- it avoids an unnecessary re-materialization of the pointer
* this doesn't matter in the case of optimized code, but in the case
of unoptimized code, this will be visible
- it avoids a potential invalid memory de-reference caused by the
indexing when the container is empty (in debug mode, clang will
normally optimize away the re-materialization in optimized builds).
The small potential behavioural change raises the question of where the
check should belong. A reasoning of defense in depth applies here, and
this does an unchecked conversion, with the assumption that users can
use the static analyzer to catch cases where we can statically identify
an invalid memory de-reference. For the cases where the static analysis
is unable to prove the size of the container, UBSan can be used to track
the invalid access.
Special thanks to Aaron Ballmann for the discussion on whether this
check would be useful and where to place it.
This also partially resolves PR26817!
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D108893
This commit is contained in:
Saleem Abdulrasool
parent
2fd180bbb9
commit
d0d9e6f084
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@ -7,6 +7,7 @@ add_clang_library(clangTidyReadabilityModule
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AvoidConstParamsInDecls.cpp
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BracesAroundStatementsCheck.cpp
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ConstReturnTypeCheck.cpp
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ContainerDataPointerCheck.cpp
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ContainerSizeEmptyCheck.cpp
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ConvertMemberFunctionsToStatic.cpp
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DeleteNullPointerCheck.cpp
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@ -0,0 +1,117 @@
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//===--- ContainerDataPointerCheck.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 "ContainerDataPointerCheck.h"
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#include "clang/Lex/Lexer.h"
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#include "llvm/ADT/StringRef.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 readability {
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ContainerDataPointerCheck::ContainerDataPointerCheck(StringRef Name,
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ClangTidyContext *Context)
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: ClangTidyCheck(Name, Context) {}
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void ContainerDataPointerCheck::registerMatchers(MatchFinder *Finder) {
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const auto Record =
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cxxRecordDecl(
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isSameOrDerivedFrom(
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namedDecl(
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has(cxxMethodDecl(isPublic(), hasName("data")).bind("data")))
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.bind("container")))
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.bind("record");
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const auto NonTemplateContainerType =
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qualType(hasUnqualifiedDesugaredType(recordType(hasDeclaration(Record))));
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const auto TemplateContainerType =
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qualType(hasUnqualifiedDesugaredType(templateSpecializationType(
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hasDeclaration(classTemplateDecl(has(Record))))));
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const auto Container =
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qualType(anyOf(NonTemplateContainerType, TemplateContainerType));
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Finder->addMatcher(
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unaryOperator(
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unless(isExpansionInSystemHeader()), hasOperatorName("&"),
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hasUnaryOperand(anyOf(
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ignoringParenImpCasts(
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cxxOperatorCallExpr(
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callee(cxxMethodDecl(hasName("operator[]"))
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.bind("operator[]")),
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argumentCountIs(2),
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hasArgument(
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0,
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anyOf(ignoringParenImpCasts(
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declRefExpr(
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to(varDecl(anyOf(
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hasType(Container),
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hasType(references(Container))))))
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.bind("var")),
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ignoringParenImpCasts(hasDescendant(
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declRefExpr(
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to(varDecl(anyOf(
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hasType(Container),
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hasType(pointsTo(Container)),
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hasType(references(Container))))))
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.bind("var"))))),
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hasArgument(1,
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ignoringParenImpCasts(
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integerLiteral(equals(0)).bind("zero"))))
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.bind("operator-call")),
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ignoringParenImpCasts(
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cxxMemberCallExpr(
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hasDescendant(
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declRefExpr(to(varDecl(anyOf(
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hasType(Container),
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hasType(references(Container))))))
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.bind("var")),
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argumentCountIs(1),
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hasArgument(0,
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ignoringParenImpCasts(
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integerLiteral(equals(0)).bind("zero"))))
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.bind("member-call")),
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ignoringParenImpCasts(
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arraySubscriptExpr(
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hasLHS(ignoringParenImpCasts(
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declRefExpr(to(varDecl(anyOf(
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hasType(Container),
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hasType(references(Container))))))
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.bind("var"))),
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hasRHS(ignoringParenImpCasts(
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integerLiteral(equals(0)).bind("zero"))))
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.bind("array-subscript")))))
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.bind("address-of"),
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this);
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}
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void ContainerDataPointerCheck::check(const MatchFinder::MatchResult &Result) {
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const auto *UO = Result.Nodes.getNodeAs<UnaryOperator>("address-of");
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const auto *DRE = Result.Nodes.getNodeAs<DeclRefExpr>("var");
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std::string ReplacementText;
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ReplacementText = std::string(Lexer::getSourceText(
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CharSourceRange::getTokenRange(DRE->getSourceRange()),
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*Result.SourceManager, getLangOpts()));
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if (DRE->getType()->isPointerType())
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ReplacementText += "->data()";
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else
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ReplacementText += ".data()";
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FixItHint Hint =
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FixItHint::CreateReplacement(UO->getSourceRange(), ReplacementText);
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diag(UO->getBeginLoc(),
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"'data' should be used for accessing the data pointer instead of taking "
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"the address of the 0-th element")
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<< Hint;
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}
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} // namespace readability
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} // namespace tidy
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} // namespace clang
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@ -0,0 +1,45 @@
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//===--- ContainerDataPointerCheck.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_READABILITY_CONTAINERDATAPOINTERCHECK_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONTAINERDATAPOINTERCHECK_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 readability {
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/// Checks whether a call to `operator[]` and `&` can be replaced with a call to
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/// `data()`.
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///
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/// This only replaces the case where the offset being accessed through the
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/// subscript operation is a known constant 0. This avoids a potential invalid
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/// memory access when the container is empty. Cases where the constant is not
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/// explictly zero can be addressed through the clang static analyzer, and those
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/// which cannot be statically identified can be caught using UBSan.
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class ContainerDataPointerCheck : public ClangTidyCheck {
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public:
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ContainerDataPointerCheck(StringRef Name, ClangTidyContext *Context);
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bool isLanguageVersionSupported(const LangOptions &LO) const override {
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return LO.CPlusPlus11;
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}
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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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llvm::Optional<TraversalKind> getCheckTraversalKind() const override {
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return TK_IgnoreUnlessSpelledInSource;
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}
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};
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} // namespace readability
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} // namespace tidy
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} // namespace clang
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONTAINERDATAPOINTERCHECK_H
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@ -12,6 +12,7 @@
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#include "AvoidConstParamsInDecls.h"
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#include "BracesAroundStatementsCheck.h"
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#include "ConstReturnTypeCheck.h"
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#include "ContainerDataPointerCheck.h"
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#include "ContainerSizeEmptyCheck.h"
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#include "ConvertMemberFunctionsToStatic.h"
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#include "DeleteNullPointerCheck.h"
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@ -62,6 +63,8 @@ public:
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"readability-braces-around-statements");
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CheckFactories.registerCheck<ConstReturnTypeCheck>(
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"readability-const-return-type");
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CheckFactories.registerCheck<ContainerDataPointerCheck>(
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"readability-container-data-pointer");
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CheckFactories.registerCheck<ContainerSizeEmptyCheck>(
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"readability-container-size-empty");
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CheckFactories.registerCheck<ConvertMemberFunctionsToStatic>(
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@ -91,6 +91,11 @@ New checks
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variables and function parameters only.
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- New :doc:`readability-data-pointer <clang-tidy/checks/readability-data-pointer` check.
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Finds cases where code could use ``data()`` rather than the address of the
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element at index 0 in a container.
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New check aliases
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^^^^^^^^^^^^^^^^^
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@ -0,0 +1,13 @@
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.. title:: clang-tidy - readability-data-pointer
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readability-data-pointer
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========================
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Finds cases where code could use ``data()`` rather than the address of the
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element at index 0 in a container. This pattern is commonly used to materialize
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a pointer to the backing data of a container. ``std::vector`` and
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``std::string`` provide a ``data()`` accessor to retrieve the data pointer which
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should be preferred.
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This also ensures that in the case that the container is empty, the data pointer
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access does not perform an errant memory access.
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@ -0,0 +1,110 @@
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// RUN: %check_clang_tidy %s readability-container-data-pointer %t
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typedef __SIZE_TYPE__ size_t;
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namespace std {
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template <typename T>
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struct vector {
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using size_type = size_t;
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vector();
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explicit vector(size_type);
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T *data();
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const T *data() const;
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T &operator[](size_type);
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const T &operator[](size_type) const;
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};
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template <typename T>
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struct basic_string {
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using size_type = size_t;
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basic_string();
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T *data();
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const T *data() const;
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T &operator[](size_t);
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const T &operator[](size_type) const;
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};
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typedef basic_string<char> string;
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typedef basic_string<wchar_t> wstring;
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template <typename T>
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struct is_integral;
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template <>
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struct is_integral<size_t> {
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static const bool value = true;
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};
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template <bool, typename T = void>
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struct enable_if { };
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template <typename T>
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struct enable_if<true, T> {
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typedef T type;
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};
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}
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template <typename T>
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void f(const T *);
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#define z (0)
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void g(size_t s) {
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std::vector<unsigned char> b(s);
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f(&((b)[(z)]));
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(b.data());{{$}}
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}
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void h() {
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std::string s;
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f(&((s).operator[]((z))));
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(s.data());{{$}}
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std::wstring w;
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f(&((&(w))->operator[]((z))));
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(w.data());{{$}}
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}
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template <typename T, typename U,
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typename = typename std::enable_if<std::is_integral<U>::value>::type>
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void i(U s) {
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std::vector<T> b(s);
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f(&b[0]);
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(b.data());{{$}}
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}
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template void i<unsigned char, size_t>(size_t);
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void j(std::vector<unsigned char> * const v) {
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f(&(*v)[0]);
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(v->data());{{$}}
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}
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void k(const std::vector<unsigned char> &v) {
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f(&v[0]);
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// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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// CHECK-FIXES: {{^ }}f(v.data());{{$}}
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}
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void l() {
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unsigned char b[32];
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f(&b[0]);
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// CHECK-MESSAGES-NOT: :[[@LINE-1]]:5: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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}
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template <typename T>
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void m(const std::vector<T> &v) {
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const T *p = &v[0];
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// CHECK-MESSAGES-NOT: :[[@LINE-1]]:16: warning: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer]
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}
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