94ca854d3c
This uses a more systematic approach for determining whcich `DeclRefExpr`s mutate the underlying object: Instead of using a few matchers, we walk up the AST until we find a parent that we can prove cannot change the underlying object. This allows us to handle most address taking and dereference, bindings to value and const& variables, and track constness of pointee (see changes in DeclRefExprUtilsTest.cpp). This allows supporting more patterns in `performance-unnecessary-copy-initialization`. Those two patterns are relatively common: ``` const auto e = (*vector_ptr)[i] ``` and ``` const auto e = vector_ptr->at(i); ``` In our codebase, we have around 25% additional findings from `performance-unnecessary-copy-initialization` with this change. I did not see any additional false positives.
67 lines
2.8 KiB
C++
67 lines
2.8 KiB
C++
//===--- DeclRefExprUtils.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_UTILS_DECLREFEXPRUTILS_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_DECLREFEXPRUTILS_H
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/Type.h"
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#include "llvm/ADT/SmallPtrSet.h"
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namespace clang::tidy::utils::decl_ref_expr {
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/// Returns set of all ``DeclRefExprs`` to ``VarDecl`` within ``Stmt``.
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llvm::SmallPtrSet<const DeclRefExpr *, 16>
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allDeclRefExprs(const VarDecl &VarDecl, const Stmt &Stmt, ASTContext &Context);
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/// Returns set of all ``DeclRefExprs`` to ``VarDecl`` within ``Decl``.
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llvm::SmallPtrSet<const DeclRefExpr *, 16>
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allDeclRefExprs(const VarDecl &VarDecl, const Decl &Decl, ASTContext &Context);
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/// Returns set of all ``DeclRefExprs`` to ``VarDecl`` within ``Stmt`` where
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/// ``VarDecl`` is guaranteed to be accessed in a const fashion.
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///
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/// If ``VarDecl`` is of pointer type, ``Indirections`` specifies the level
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/// of indirection of the object whose mutations we are tracking.
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///
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/// For example, given:
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/// ```
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/// int i;
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/// int* p;
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/// p = &i; // (A)
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/// *p = 3; // (B)
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/// ```
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///
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/// - `constReferenceDeclRefExprs(P, Stmt, Context, 0)` returns the reference
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// to `p` in (B): the pointee is modified, but the pointer is not;
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/// - `constReferenceDeclRefExprs(P, Stmt, Context, 1)` returns the reference
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// to `p` in (A): the pointee is modified, but the pointer is not;
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llvm::SmallPtrSet<const DeclRefExpr *, 16>
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constReferenceDeclRefExprs(const VarDecl &VarDecl, const Stmt &Stmt,
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ASTContext &Context, int Indirections);
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/// Returns true if all ``DeclRefExpr`` to the variable within ``Stmt``
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/// do not modify it.
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/// See `constReferenceDeclRefExprs` for the meaning of ``Indirections``.
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bool isOnlyUsedAsConst(const VarDecl &Var, const Stmt &Stmt,
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ASTContext &Context, int Indirections);
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/// Returns ``true`` if ``DeclRefExpr`` is the argument of a copy-constructor
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/// call expression within ``Decl``.
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bool isCopyConstructorArgument(const DeclRefExpr &DeclRef, const Decl &Decl,
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ASTContext &Context);
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/// Returns ``true`` if ``DeclRefExpr`` is the argument of a copy-assignment
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/// operator CallExpr within ``Decl``.
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bool isCopyAssignmentArgument(const DeclRefExpr &DeclRef, const Decl &Decl,
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ASTContext &Context);
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} // namespace clang::tidy::utils::decl_ref_expr
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_DECLREFEXPRUTILS_H
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