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diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
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+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
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+//===--- UseNullptrCheck.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 "UseNullptrCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/ADT/StringExtras.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+using namespace llvm;
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+const char CastSequence[] = "sequence";
+
+/// \brief Matches cast expressions that have a cast kind of CK_NullToPointer
+/// or CK_NullToMemberPointer.
+///
+/// Given
+/// \code
+/// int *p = 0;
+/// \endcode
+/// implicitCastExpr(isNullToPointer()) matches the implicit cast clang adds
+/// around \c 0.
+AST_MATCHER(CastExpr, isNullToPointer) {
+ return Node.getCastKind() == CK_NullToPointer ||
+ Node.getCastKind() == CK_NullToMemberPointer;
+}
+
+AST_MATCHER(Type, sugaredNullptrType) {
+ const Type *DesugaredType = Node.getUnqualifiedDesugaredType();
+ if (const BuiltinType *BT = dyn_cast<BuiltinType>(DesugaredType))
+ return BT->getKind() == BuiltinType::NullPtr;
+ return false;
+}
+
+/// \brief Create a matcher that finds implicit casts as well as the head of a
+/// sequence of zero or more nested explicit casts that have an implicit cast
+/// to null within.
+/// Finding sequences of explict casts is necessary so that an entire sequence
+/// can be replaced instead of just the inner-most implicit cast.
+StatementMatcher makeCastSequenceMatcher() {
+ StatementMatcher ImplicitCastToNull = implicitCastExpr(
+ isNullToPointer(),
+ unless(hasSourceExpression(hasType(sugaredNullptrType()))));
+
+ return castExpr(anyOf(ImplicitCastToNull,
+ explicitCastExpr(hasDescendant(ImplicitCastToNull))),
+ unless(hasAncestor(explicitCastExpr())))
+ .bind(CastSequence);
+}
+
+bool isReplaceableRange(SourceLocation StartLoc, SourceLocation EndLoc,
+ const SourceManager &SM) {
+ return SM.isWrittenInSameFile(StartLoc, EndLoc);
+}
+
+/// \brief Replaces the provided range with the text "nullptr", but only if
+/// the start and end location are both in main file.
+/// Returns true if and only if a replacement was made.
+void replaceWithNullptr(ClangTidyCheck &Check, SourceManager &SM,
+ SourceLocation StartLoc, SourceLocation EndLoc) {
+ CharSourceRange Range(SourceRange(StartLoc, EndLoc), true);
+ // Add a space if nullptr follows an alphanumeric character. This happens
+ // whenever there is an c-style explicit cast to nullptr not surrounded by
+ // parentheses and right beside a return statement.
+ SourceLocation PreviousLocation = StartLoc.getLocWithOffset(-1);
+ bool NeedsSpace = isAlphanumeric(*SM.getCharacterData(PreviousLocation));
+ Check.diag(Range.getBegin(), "use nullptr") << FixItHint::CreateReplacement(
+ Range, NeedsSpace ? " nullptr" : "nullptr");
+}
+
+/// \brief Returns the name of the outermost macro.
+///
+/// Given
+/// \code
+/// #define MY_NULL NULL
+/// \endcode
+/// If \p Loc points to NULL, this function will return the name MY_NULL.
+StringRef getOutermostMacroName(SourceLocation Loc, const SourceManager &SM,
+ const LangOptions &LO) {
+ assert(Loc.isMacroID());
+ SourceLocation OutermostMacroLoc;
+
+ while (Loc.isMacroID()) {
+ OutermostMacroLoc = Loc;
+ Loc = SM.getImmediateMacroCallerLoc(Loc);
+ }
+
+ return Lexer::getImmediateMacroName(OutermostMacroLoc, SM, LO);
+}
+
+/// \brief RecursiveASTVisitor for ensuring all nodes rooted at a given AST
+/// subtree that have file-level source locations corresponding to a macro
+/// argument have implicit NullTo(Member)Pointer nodes as ancestors.
+class MacroArgUsageVisitor : public RecursiveASTVisitor<MacroArgUsageVisitor> {
+public:
+ MacroArgUsageVisitor(SourceLocation CastLoc, const SourceManager &SM)
+ : CastLoc(CastLoc), SM(SM), Visited(false), CastFound(false),
+ InvalidFound(false) {
+ assert(CastLoc.isFileID());
+ }
+
+ bool TraverseStmt(Stmt *S) {
+ bool VisitedPreviously = Visited;
+
+ if (!RecursiveASTVisitor<MacroArgUsageVisitor>::TraverseStmt(S))
+ return false;
+
+ // The point at which VisitedPreviously is false and Visited is true is the
+ // root of a subtree containing nodes whose locations match CastLoc. It's
+ // at this point we test that the Implicit NullTo(Member)Pointer cast was
+ // found or not.
+ if (!VisitedPreviously) {
+ if (Visited && !CastFound) {
+ // Found nodes with matching SourceLocations but didn't come across a
+ // cast. This is an invalid macro arg use. Can stop traversal
+ // completely now.
+ InvalidFound = true;
+ return false;
+ }
+ // Reset state as we unwind back up the tree.
+ CastFound = false;
+ Visited = false;
+ }
+ return true;
+ }
+
+ bool VisitStmt(Stmt *S) {
+ if (SM.getFileLoc(S->getLocStart()) != CastLoc)
+ return true;
+ Visited = true;
+
+ const ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(S);
+ if (Cast && (Cast->getCastKind() == CK_NullToPointer ||
+ Cast->getCastKind() == CK_NullToMemberPointer))
+ CastFound = true;
+
+ return true;
+ }
+
+ bool foundInvalid() const { return InvalidFound; }
+
+private:
+ SourceLocation CastLoc;
+ const SourceManager &SM;
+
+ bool Visited;
+ bool CastFound;
+ bool InvalidFound;
+};
+
+/// \brief Looks for implicit casts as well as sequences of 0 or more explicit
+/// casts with an implicit null-to-pointer cast within.
+///
+/// The matcher this visitor is used with will find a single implicit cast or a
+/// top-most explicit cast (i.e. it has no explicit casts as an ancestor) where
+/// an implicit cast is nested within. However, there is no guarantee that only
+/// explicit casts exist between the found top-most explicit cast and the
+/// possibly more than one nested implicit cast. This visitor finds all cast
+/// sequences with an implicit cast to null within and creates a replacement
+/// leaving the outermost explicit cast unchanged to avoid introducing
+/// ambiguities.
+class CastSequenceVisitor : public RecursiveASTVisitor<CastSequenceVisitor> {
+public:
+ CastSequenceVisitor(ASTContext &Context, ArrayRef<StringRef> NullMacros,
+ ClangTidyCheck &check)
+ : SM(Context.getSourceManager()), Context(Context),
+ NullMacros(NullMacros), Check(check), FirstSubExpr(nullptr),
+ PruneSubtree(false) {}
+
+ bool TraverseStmt(Stmt *S) {
+ // Stop traversing down the tree if requested.
+ if (PruneSubtree) {
+ PruneSubtree = false;
+ return true;
+ }
+ return RecursiveASTVisitor<CastSequenceVisitor>::TraverseStmt(S);
+ }
+
+ // Only VisitStmt is overridden as we shouldn't find other base AST types
+ // within a cast expression.
+ bool VisitStmt(Stmt *S) {
+ CastExpr *C = dyn_cast<CastExpr>(S);
+ if (!C) {
+ FirstSubExpr = nullptr;
+ return true;
+ }
+ if (!FirstSubExpr)
+ FirstSubExpr = C->getSubExpr()->IgnoreParens();
+
+ if (C->getCastKind() != CK_NullToPointer &&
+ C->getCastKind() != CK_NullToMemberPointer) {
+ return true;
+ }
+
+ SourceLocation StartLoc = FirstSubExpr->getLocStart();
+ SourceLocation EndLoc = FirstSubExpr->getLocEnd();
+
+ // If the location comes from a macro arg expansion, *all* uses of that
+ // arg must be checked to result in NullTo(Member)Pointer casts.
+ //
+ // If the location comes from a macro body expansion, check to see if its
+ // coming from one of the allowed 'NULL' macros.
+ if (SM.isMacroArgExpansion(StartLoc) && SM.isMacroArgExpansion(EndLoc)) {
+ SourceLocation FileLocStart = SM.getFileLoc(StartLoc),
+ FileLocEnd = SM.getFileLoc(EndLoc);
+ if (isReplaceableRange(FileLocStart, FileLocEnd, SM) &&
+ allArgUsesValid(C)) {
+ replaceWithNullptr(Check, SM, FileLocStart, FileLocEnd);
+ }
+ return skipSubTree();
+ }
+
+ if (SM.isMacroBodyExpansion(StartLoc) && SM.isMacroBodyExpansion(EndLoc)) {
+ StringRef OutermostMacroName =
+ getOutermostMacroName(StartLoc, SM, Context.getLangOpts());
+
+ // Check to see if the user wants to replace the macro being expanded.
+ if (std::find(NullMacros.begin(), NullMacros.end(), OutermostMacroName) ==
+ NullMacros.end()) {
+ return skipSubTree();
+ }
+
+ StartLoc = SM.getFileLoc(StartLoc);
+ EndLoc = SM.getFileLoc(EndLoc);
+ }
+
+ if (!isReplaceableRange(StartLoc, EndLoc, SM)) {
+ return skipSubTree();
+ }
+ replaceWithNullptr(Check, SM, StartLoc, EndLoc);
+
+ return skipSubTree();
+ }
+
+private:
+ bool skipSubTree() {
+ PruneSubtree = true;
+ return true;
+ }
+
+ /// \brief Tests that all expansions of a macro arg, one of which expands to
+ /// result in \p CE, yield NullTo(Member)Pointer casts.
+ bool allArgUsesValid(const CastExpr *CE) {
+ SourceLocation CastLoc = CE->getLocStart();
+
+ // Step 1: Get location of macro arg and location of the macro the arg was
+ // provided to.
+ SourceLocation ArgLoc, MacroLoc;
+ if (!getMacroAndArgLocations(CastLoc, ArgLoc, MacroLoc))
+ return false;
+
+ // Step 2: Find the first ancestor that doesn't expand from this macro.
+ ast_type_traits::DynTypedNode ContainingAncestor;
+ if (!findContainingAncestor(
+ ast_type_traits::DynTypedNode::create<Stmt>(*CE), MacroLoc,
+ ContainingAncestor))
+ return false;
+
+ // Step 3:
+ // Visit children of this containing parent looking for the least-descended
+ // nodes of the containing parent which are macro arg expansions that expand
+ // from the given arg location.
+ // Visitor needs: arg loc
+ MacroArgUsageVisitor ArgUsageVisitor(SM.getFileLoc(CastLoc), SM);
+ if (const auto *D = ContainingAncestor.get<Decl>())
+ ArgUsageVisitor.TraverseDecl(const_cast<Decl *>(D));
+ else if (const auto *S = ContainingAncestor.get<Stmt>())
+ ArgUsageVisitor.TraverseStmt(const_cast<Stmt *>(S));
+ else
+ llvm_unreachable("Unhandled ContainingAncestor node type");
+
+ return !ArgUsageVisitor.foundInvalid();
+ }
+
+ /// \brief Given the SourceLocation for a macro arg expansion, finds the
+ /// non-macro SourceLocation of the macro the arg was passed to and the
+ /// non-macro SourceLocation of the argument in the arg list to that macro.
+ /// These results are returned via \c MacroLoc and \c ArgLoc respectively.
+ /// These values are undefined if the return value is false.
+ ///
+ /// \returns false if one of the returned SourceLocations would be a
+ /// SourceLocation pointing within the definition of another macro.
+ bool getMacroAndArgLocations(SourceLocation Loc, SourceLocation &ArgLoc,
+ SourceLocation &MacroLoc) {
+ assert(Loc.isMacroID() && "Only reasonble to call this on macros");
+
+ ArgLoc = Loc;
+
+ // Find the location of the immediate macro expansion.
+ while (true) {
+ std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(ArgLoc);
+ const SrcMgr::SLocEntry *E = &SM.getSLocEntry(LocInfo.first);
+ const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
+
+ SourceLocation OldArgLoc = ArgLoc;
+ ArgLoc = Expansion.getExpansionLocStart();
+ if (!Expansion.isMacroArgExpansion()) {
+ if (!MacroLoc.isFileID())
+ return false;
+
+ StringRef Name =
+ Lexer::getImmediateMacroName(OldArgLoc, SM, Context.getLangOpts());
+ return std::find(NullMacros.begin(), NullMacros.end(), Name) !=
+ NullMacros.end();
+ }
+
+ MacroLoc = SM.getImmediateExpansionRange(ArgLoc).first;
+
+ ArgLoc = Expansion.getSpellingLoc().getLocWithOffset(LocInfo.second);
+ if (ArgLoc.isFileID())
+ return true;
+
+ // If spelling location resides in the same FileID as macro expansion
+ // location, it means there is no inner macro.
+ FileID MacroFID = SM.getFileID(MacroLoc);
+ if (SM.isInFileID(ArgLoc, MacroFID)) {
+ // Don't transform this case. If the characters that caused the
+ // null-conversion come from within a macro, they can't be changed.
+ return false;
+ }
+ }
+
+ llvm_unreachable("getMacroAndArgLocations");
+ }
+
+ /// \brief Tests if TestMacroLoc is found while recursively unravelling
+ /// expansions starting at TestLoc. TestMacroLoc.isFileID() must be true.
+ /// Implementation is very similar to getMacroAndArgLocations() except in this
+ /// case, it's not assumed that TestLoc is expanded from a macro argument.
+ /// While unravelling expansions macro arguments are handled as with
+ /// getMacroAndArgLocations() but in this function macro body expansions are
+ /// also handled.
+ ///
+ /// False means either:
+ /// - TestLoc is not from a macro expansion
+ /// - TestLoc is from a different macro expansion
+ bool expandsFrom(SourceLocation TestLoc, SourceLocation TestMacroLoc) {
+ if (TestLoc.isFileID()) {
+ return false;
+ }
+
+ SourceLocation Loc = TestLoc, MacroLoc;
+
+ while (true) {
+ std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
+ const SrcMgr::SLocEntry *E = &SM.getSLocEntry(LocInfo.first);
+ const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
+
+ Loc = Expansion.getExpansionLocStart();
+
+ if (!Expansion.isMacroArgExpansion()) {
+ if (Loc.isFileID()) {
+ return Loc == TestMacroLoc;
+ }
+ // Since Loc is still a macro ID and it's not an argument expansion, we
+ // don't need to do the work of handling an argument expansion. Simply
+ // keep recursively expanding until we hit a FileID or a macro arg
+ // expansion or a macro arg expansion.
+ continue;
+ }
+
+ MacroLoc = SM.getImmediateExpansionRange(Loc).first;
+ if (MacroLoc.isFileID() && MacroLoc == TestMacroLoc) {
+ // Match made.
+ return true;
+ }
+
+ Loc = Expansion.getSpellingLoc().getLocWithOffset(LocInfo.second);
+ if (Loc.isFileID()) {
+ // If we made it this far without finding a match, there is no match to
+ // be made.
+ return false;
+ }
+ }
+
+ llvm_unreachable("expandsFrom");
+ }
+
+ /// \brief Given a starting point \c Start in the AST, find an ancestor that
+ /// doesn't expand from the macro called at file location \c MacroLoc.
+ ///
+ /// \pre MacroLoc.isFileID()
+ /// \returns true if such an ancestor was found, false otherwise.
+ bool findContainingAncestor(ast_type_traits::DynTypedNode Start,
+ SourceLocation MacroLoc,
+ ast_type_traits::DynTypedNode &Result) {
+ // Below we're only following the first parent back up the AST. This should
+ // be fine since for the statements we care about there should only be one
+ // parent as far up as we care. If this assumption doesn't hold, need to
+ // revisit what to do here.
+
+ assert(MacroLoc.isFileID());
+
+ while (true) {
+ const auto &Parents = Context.getParents(Start);
+ if (Parents.empty())
+ return false;
+ assert(Parents.size() == 1 &&
+ "Found an ancestor with more than one parent!");
+
+ const ast_type_traits::DynTypedNode &Parent = Parents[0];
+
+ SourceLocation Loc;
+ if (const auto *D = Parent.get<Decl>())
+ Loc = D->getLocStart();
+ else if (const auto *S = Parent.get<Stmt>())
+ Loc = S->getLocStart();
+ else
+ llvm_unreachable("Expected to find Decl or Stmt containing ancestor");
+
+ if (!expandsFrom(Loc, MacroLoc)) {
+ Result = Parent;
+ return true;
+ }
+ Start = Parent;
+ }
+
+ llvm_unreachable("findContainingAncestor");
+ }
+
+private:
+ SourceManager &SM;
+ ASTContext &Context;
+ ArrayRef<StringRef> NullMacros;
+ ClangTidyCheck &Check;
+ Expr *FirstSubExpr;
+ bool PruneSubtree;
+};
+
+UseNullptrCheck::UseNullptrCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {
+ StringRef MacrosStr = Options.get("NullMacros", "");
+ MacrosStr.split(NullMacros, ",");
+}
+
+void UseNullptrCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "NullMacros",
+ llvm::join(NullMacros.begin(), NullMacros.end(), ","));
+}
+
+void UseNullptrCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(makeCastSequenceMatcher(), this);
+}
+
+void UseNullptrCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *NullCast = Result.Nodes.getNodeAs<CastExpr>(CastSequence);
+ assert(NullCast && "Bad Callback. No node provided");
+
+ // Given an implicit null-ptr cast or an explicit cast with an implicit
+ // null-to-pointer cast within use CastSequenceVisitor to identify sequences
+ // of explicit casts that can be converted into 'nullptr'.
+ CastSequenceVisitor(*Result.Context, NullMacros, *this)
+ .TraverseStmt(const_cast<CastExpr *>(NullCast));
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang
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