================ @@ -0,0 +1,204 @@ +//===--- InferAlloc.cpp - Allocation type inference -----------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// +// +// This file implements allocation-related type inference. +// +//===----------------------------------------------------------------------===// + +#include "clang/AST/InferAlloc.h" +#include "clang/AST/ASTContext.h" +#include "clang/AST/Decl.h" +#include "clang/AST/DeclCXX.h" +#include "clang/AST/Expr.h" +#include "clang/AST/Type.h" +#include "clang/Basic/IdentifierTable.h" +#include "llvm/ADT/SmallPtrSet.h" + +namespace clang { +namespace { +bool typeContainsPointer(QualType T, + llvm::SmallPtrSet<const RecordDecl *, 4> &VisitedRD, + bool &IncompleteType) { + QualType CanonicalType = T.getCanonicalType(); + if (CanonicalType->isPointerType()) + return true; // base case + + // Look through typedef chain to check for special types. + for (QualType CurrentT = T; const auto *TT = CurrentT->getAs<TypedefType>(); + CurrentT = TT->getDecl()->getUnderlyingType()) { + const IdentifierInfo *II = TT->getDecl()->getIdentifier(); + // Special Case: Syntactically uintptr_t is not a pointer; semantically, + // however, very likely used as such. Therefore, classify uintptr_t as a + // pointer, too. + if (II && II->isStr("uintptr_t")) + return true; + } + + // The type is an array; check the element type. + if (const ArrayType *AT = dyn_cast<ArrayType>(CanonicalType)) + return typeContainsPointer(AT->getElementType(), VisitedRD, IncompleteType); + // The type is a struct, class, or union. + if (const RecordDecl *RD = CanonicalType->getAsRecordDecl()) { + if (!RD->isCompleteDefinition()) { + IncompleteType = true; + return false; + } + if (!VisitedRD.insert(RD).second) + return false; // already visited + // Check all fields. + for (const FieldDecl *Field : RD->fields()) { + if (typeContainsPointer(Field->getType(), VisitedRD, IncompleteType)) + return true; + } + // For C++ classes, also check base classes. + if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD)) { + // Polymorphic types require a vptr. + if (CXXRD->isDynamicClass()) + return true; + for (const CXXBaseSpecifier &Base : CXXRD->bases()) { + if (typeContainsPointer(Base.getType(), VisitedRD, IncompleteType)) + return true; + } + } + } + return false; +} + +/// Infer type from a simple sizeof expression. +QualType inferTypeFromSizeofExpr(const Expr *E) { + const Expr *Arg = E->IgnoreParenImpCasts(); + if (const auto *UET = dyn_cast<UnaryExprOrTypeTraitExpr>(Arg)) { + if (UET->getKind() == UETT_SizeOf) { + if (UET->isArgumentType()) + return UET->getArgumentTypeInfo()->getType(); + else + return UET->getArgumentExpr()->getType(); + } + } + return QualType(); +} + +/// Infer type from an arithmetic expression involving a sizeof. For example: +/// +/// malloc(sizeof(MyType) + padding); // infers 'MyType' +/// malloc(sizeof(MyType) * 32); // infers 'MyType' +/// malloc(32 * sizeof(MyType)); // infers 'MyType' +/// malloc(sizeof(MyType) << 1); // infers 'MyType' +/// ... +/// +/// More complex arithmetic expressions are supported, but are a heuristic, e.g. +/// when considering allocations for structs with flexible array members: +/// +/// malloc(sizeof(HasFlexArray) + sizeof(int) * 32); // infers 'HasFlexArray' +/// +QualType inferPossibleTypeFromArithSizeofExpr(const Expr *E) { + const Expr *Arg = E->IgnoreParenImpCasts(); + // The argument is a lone sizeof expression. + if (QualType T = inferTypeFromSizeofExpr(Arg); !T.isNull()) + return T; + if (const auto *BO = dyn_cast<BinaryOperator>(Arg)) { + // Argument is an arithmetic expression. Cover common arithmetic patterns + // involving sizeof. + switch (BO->getOpcode()) { + case BO_Add: + case BO_Div: + case BO_Mul: + case BO_Shl: + case BO_Shr: + case BO_Sub: + if (QualType T = inferPossibleTypeFromArithSizeofExpr(BO->getLHS()); + !T.isNull()) + return T; + if (QualType T = inferPossibleTypeFromArithSizeofExpr(BO->getRHS()); + !T.isNull()) + return T; + break; + default: + break; + } + } + return QualType(); +} + +/// If the expression E is a reference to a variable, infer the type from a +/// variable's initializer if it contains a sizeof. Beware, this is a heuristic +/// and ignores if a variable is later reassigned. For example: +/// +/// size_t my_size = sizeof(MyType); +/// void *x = malloc(my_size); // infers 'MyType' +/// +QualType inferPossibleTypeFromVarInitSizeofExpr(const Expr *E) { + const Expr *Arg = E->IgnoreParenImpCasts(); + if (const auto *DRE = dyn_cast<DeclRefExpr>(Arg)) { + if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) { + if (const Expr *Init = VD->getInit()) + return inferPossibleTypeFromArithSizeofExpr(Init); + } + } + return QualType(); +} + +/// Deduces the allocated type by checking if the allocation call's result +/// is immediately used in a cast expression. For example: +/// +/// MyType *x = (MyType *)malloc(4096); // infers 'MyType' +/// +QualType inferPossibleTypeFromCastExpr(const CallExpr *CallE, + const CastExpr *CastE) { + if (!CastE) + return QualType(); + QualType PtrType = CastE->getType(); + if (PtrType->isPointerType()) + return PtrType->getPointeeType(); + return QualType(); +} +} // anonymous namespace + +namespace infer_alloc { + +QualType inferPossibleType(const CallExpr *E, const ASTContext &Ctx, ---------------- fmayer wrote:
https://llvm.org/docs/CodingStandards.html#use-namespace-qualifiers-to-implement-previously-declared-functions https://github.com/llvm/llvm-project/pull/163636 _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
