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llvm-project/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
Matheus Izvekov 15f3cd6bfc
[clang] Implement ElaboratedType sugaring for types written bare 
Without this patch, clang will not wrap in an ElaboratedType node types written
without a keyword and nested name qualifier, which goes against the intent that
we should produce an AST which retains enough details to recover how things are
written.

The lack of this sugar is incompatible with the intent of the type printer
default policy, which is to print types as written, but to fall back and print
them fully qualified when they are desugared.

An ElaboratedTypeLoc without keyword / NNS uses no storage by itself, but still
requires pointer alignment due to pre-existing bug in the TypeLoc buffer
handling.

---

Troubleshooting list to deal with any breakage seen with this patch:

1) The most likely effect one would see by this patch is a change in how
   a type is printed. The type printer will, by design and default,
   print types as written. There are customization options there, but
   not that many, and they mainly apply to how to print a type that we
   somehow failed to track how it was written. This patch fixes a
   problem where we failed to distinguish between a type
   that was written without any elaborated-type qualifiers,
   such as a 'struct'/'class' tags and name spacifiers such as 'std::',
   and one that has been stripped of any 'metadata' that identifies such,
   the so called canonical types.
   Example:
   ```
   namespace foo {
     struct A {};
     A a;
   };
   ```
   If one were to print the type of `foo::a`, prior to this patch, this
   would result in `foo::A`. This is how the type printer would have,
   by default, printed the canonical type of A as well.
   As soon as you add any name qualifiers to A, the type printer would
   suddenly start accurately printing the type as written. This patch
   will make it print it accurately even when written without
   qualifiers, so we will just print `A` for the initial example, as
   the user did not really write that `foo::` namespace qualifier.

2) This patch could expose a bug in some AST matcher. Matching types
   is harder to get right when there is sugar involved. For example,
   if you want to match a type against being a pointer to some type A,
   then you have to account for getting a type that is sugar for a
   pointer to A, or being a pointer to sugar to A, or both! Usually
   you would get the second part wrong, and this would work for a
   very simple test where you don't use any name qualifiers, but
   you would discover is broken when you do. The usual fix is to
   either use the matcher which strips sugar, which is annoying
   to use as for example if you match an N level pointer, you have
   to put N+1 such matchers in there, beginning to end and between
   all those levels. But in a lot of cases, if the property you want
   to match is present in the canonical type, it's easier and faster
   to just match on that... This goes with what is said in 1), if
   you want to match against the name of a type, and you want
   the name string to be something stable, perhaps matching on
   the name of the canonical type is the better choice.

3) This patch could expose a bug in how you get the source range of some
   TypeLoc. For some reason, a lot of code is using getLocalSourceRange(),
   which only looks at the given TypeLoc node. This patch introduces a new,
   and more common TypeLoc node which contains no source locations on itself.
   This is not an inovation here, and some other, more rare TypeLoc nodes could
   also have this property, but if you use getLocalSourceRange on them, it's not
   going to return any valid locations, because it doesn't have any. The right fix
   here is to always use getSourceRange() or getBeginLoc/getEndLoc which will dive
   into the inner TypeLoc to get the source range if it doesn't find it on the
   top level one. You can use getLocalSourceRange if you are really into
   micro-optimizations and you have some outside knowledge that the TypeLocs you are
   dealing with will always include some source location.

4) Exposed a bug somewhere in the use of the normal clang type class API, where you
   have some type, you want to see if that type is some particular kind, you try a
   `dyn_cast` such as `dyn_cast<TypedefType>` and that fails because now you have an
   ElaboratedType which has a TypeDefType inside of it, which is what you wanted to match.
   Again, like 2), this would usually have been tested poorly with some simple tests with
   no qualifications, and would have been broken had there been any other kind of type sugar,
   be it an ElaboratedType or a TemplateSpecializationType or a SubstTemplateParmType.
   The usual fix here is to use `getAs` instead of `dyn_cast`, which will look deeper
   into the type. Or use `getAsAdjusted` when dealing with TypeLocs.
   For some reason the API is inconsistent there and on TypeLocs getAs behaves like a dyn_cast.

5) It could be a bug in this patch perhaps.

Let me know if you need any help!

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Differential Revision: https://reviews.llvm.org/D112374
2022-07-27 11:10:54 +02:00

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//===--- LoopConvertCheck.cpp - clang-tidy---------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "LoopConvertCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/Lexer.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstring>
#include <utility>
using namespace clang::ast_matchers;
using namespace llvm;
namespace clang {
namespace tidy {
template <> struct OptionEnumMapping<modernize::Confidence::Level> {
static llvm::ArrayRef<std::pair<modernize::Confidence::Level, StringRef>>
getEnumMapping() {
static constexpr std::pair<modernize::Confidence::Level, StringRef>
Mapping[] = {{modernize::Confidence::CL_Reasonable, "reasonable"},
{modernize::Confidence::CL_Safe, "safe"},
{modernize::Confidence::CL_Risky, "risky"}};
return makeArrayRef(Mapping);
}
};
template <> struct OptionEnumMapping<modernize::VariableNamer::NamingStyle> {
static llvm::ArrayRef<
std::pair<modernize::VariableNamer::NamingStyle, StringRef>>
getEnumMapping() {
static constexpr std::pair<modernize::VariableNamer::NamingStyle, StringRef>
Mapping[] = {{modernize::VariableNamer::NS_CamelCase, "CamelCase"},
{modernize::VariableNamer::NS_CamelBack, "camelBack"},
{modernize::VariableNamer::NS_LowerCase, "lower_case"},
{modernize::VariableNamer::NS_UpperCase, "UPPER_CASE"}};
return makeArrayRef(Mapping);
}
};
namespace modernize {
static const char LoopNameArray[] = "forLoopArray";
static const char LoopNameIterator[] = "forLoopIterator";
static const char LoopNameReverseIterator[] = "forLoopReverseIterator";
static const char LoopNamePseudoArray[] = "forLoopPseudoArray";
static const char ConditionBoundName[] = "conditionBound";
static const char InitVarName[] = "initVar";
static const char BeginCallName[] = "beginCall";
static const char EndCallName[] = "endCall";
static const char EndVarName[] = "endVar";
static const char DerefByValueResultName[] = "derefByValueResult";
static const char DerefByRefResultName[] = "derefByRefResult";
static const StatementMatcher integerComparisonMatcher() {
return expr(ignoringParenImpCasts(
declRefExpr(to(varDecl(equalsBoundNode(InitVarName))))));
}
static const DeclarationMatcher initToZeroMatcher() {
return varDecl(
hasInitializer(ignoringParenImpCasts(integerLiteral(equals(0)))))
.bind(InitVarName);
}
static const StatementMatcher incrementVarMatcher() {
return declRefExpr(to(varDecl(equalsBoundNode(InitVarName))));
}
static StatementMatcher
arrayConditionMatcher(internal::Matcher<Expr> LimitExpr) {
return binaryOperator(
anyOf(allOf(hasOperatorName("<"), hasLHS(integerComparisonMatcher()),
hasRHS(LimitExpr)),
allOf(hasOperatorName(">"), hasLHS(LimitExpr),
hasRHS(integerComparisonMatcher())),
allOf(hasOperatorName("!="),
hasOperands(integerComparisonMatcher(), LimitExpr))));
}
/// The matcher for loops over arrays.
/// \code
/// for (int i = 0; i < 3 + 2; ++i) { ... }
/// \endcode
/// The following string identifiers are bound to these parts of the AST:
/// ConditionBoundName: '3 + 2' (as an Expr)
/// InitVarName: 'i' (as a VarDecl)
/// LoopName: The entire for loop (as a ForStmt)
///
/// Client code will need to make sure that:
/// - The index variable is only used as an array index.
/// - All arrays indexed by the loop are the same.
StatementMatcher makeArrayLoopMatcher() {
StatementMatcher ArrayBoundMatcher =
expr(hasType(isInteger())).bind(ConditionBoundName);
return forStmt(unless(isInTemplateInstantiation()),
hasLoopInit(declStmt(hasSingleDecl(initToZeroMatcher()))),
hasCondition(arrayConditionMatcher(ArrayBoundMatcher)),
hasIncrement(
unaryOperator(hasOperatorName("++"),
hasUnaryOperand(incrementVarMatcher()))))
.bind(LoopNameArray);
}
/// The matcher used for iterator-based for loops.
///
/// This matcher is more flexible than array-based loops. It will match
/// catch loops of the following textual forms (regardless of whether the
/// iterator type is actually a pointer type or a class type):
///
/// \code
/// for (containerType::iterator it = container.begin(),
/// e = createIterator(); it != e; ++it) { ... }
/// for (containerType::iterator it = container.begin();
/// it != anotherContainer.end(); ++it) { ... }
/// \endcode
/// The following string identifiers are bound to the parts of the AST:
/// InitVarName: 'it' (as a VarDecl)
/// LoopName: The entire for loop (as a ForStmt)
/// In the first example only:
/// EndVarName: 'e' (as a VarDecl)
/// In the second example only:
/// EndCallName: 'container.end()' (as a CXXMemberCallExpr)
///
/// Client code will need to make sure that:
/// - The two containers on which 'begin' and 'end' are called are the same.
StatementMatcher makeIteratorLoopMatcher(bool IsReverse) {
auto BeginNameMatcher = IsReverse ? hasAnyName("rbegin", "crbegin")
: hasAnyName("begin", "cbegin");
auto EndNameMatcher =
IsReverse ? hasAnyName("rend", "crend") : hasAnyName("end", "cend");
StatementMatcher BeginCallMatcher =
cxxMemberCallExpr(argumentCountIs(0),
callee(cxxMethodDecl(BeginNameMatcher)))
.bind(BeginCallName);
DeclarationMatcher InitDeclMatcher =
varDecl(hasInitializer(anyOf(ignoringParenImpCasts(BeginCallMatcher),
materializeTemporaryExpr(
ignoringParenImpCasts(BeginCallMatcher)),
hasDescendant(BeginCallMatcher))))
.bind(InitVarName);
DeclarationMatcher EndDeclMatcher =
varDecl(hasInitializer(anything())).bind(EndVarName);
StatementMatcher EndCallMatcher = cxxMemberCallExpr(
argumentCountIs(0), callee(cxxMethodDecl(EndNameMatcher)));
StatementMatcher IteratorBoundMatcher =
expr(anyOf(ignoringParenImpCasts(
declRefExpr(to(varDecl(equalsBoundNode(EndVarName))))),
ignoringParenImpCasts(expr(EndCallMatcher).bind(EndCallName)),
materializeTemporaryExpr(ignoringParenImpCasts(
expr(EndCallMatcher).bind(EndCallName)))));
StatementMatcher IteratorComparisonMatcher = expr(ignoringParenImpCasts(
declRefExpr(to(varDecl(equalsBoundNode(InitVarName))))));
// This matcher tests that a declaration is a CXXRecordDecl that has an
// overloaded operator*(). If the operator*() returns by value instead of by
// reference then the return type is tagged with DerefByValueResultName.
internal::Matcher<VarDecl> TestDerefReturnsByValue =
hasType(hasUnqualifiedDesugaredType(
recordType(hasDeclaration(cxxRecordDecl(hasMethod(cxxMethodDecl(
hasOverloadedOperatorName("*"),
anyOf(
// Tag the return type if it's by value.
returns(qualType(unless(hasCanonicalType(referenceType())))
.bind(DerefByValueResultName)),
returns(
// Skip loops where the iterator's operator* returns an
// rvalue reference. This is just weird.
qualType(unless(hasCanonicalType(rValueReferenceType())))
.bind(DerefByRefResultName))))))))));
return forStmt(
unless(isInTemplateInstantiation()),
hasLoopInit(anyOf(declStmt(declCountIs(2),
containsDeclaration(0, InitDeclMatcher),
containsDeclaration(1, EndDeclMatcher)),
declStmt(hasSingleDecl(InitDeclMatcher)))),
hasCondition(ignoringImplicit(binaryOperation(
hasOperatorName("!="), hasOperands(IteratorComparisonMatcher,
IteratorBoundMatcher)))),
hasIncrement(anyOf(
unaryOperator(hasOperatorName("++"),
hasUnaryOperand(declRefExpr(
to(varDecl(equalsBoundNode(InitVarName)))))),
cxxOperatorCallExpr(
hasOverloadedOperatorName("++"),
hasArgument(0, declRefExpr(to(
varDecl(equalsBoundNode(InitVarName),
TestDerefReturnsByValue))))))))
.bind(IsReverse ? LoopNameReverseIterator : LoopNameIterator);
}
/// The matcher used for array-like containers (pseudoarrays).
///
/// This matcher is more flexible than array-based loops. It will match
/// loops of the following textual forms (regardless of whether the
/// iterator type is actually a pointer type or a class type):
///
/// \code
/// for (int i = 0, j = container.size(); i < j; ++i) { ... }
/// for (int i = 0; i < container.size(); ++i) { ... }
/// \endcode
/// The following string identifiers are bound to the parts of the AST:
/// InitVarName: 'i' (as a VarDecl)
/// LoopName: The entire for loop (as a ForStmt)
/// In the first example only:
/// EndVarName: 'j' (as a VarDecl)
/// In the second example only:
/// EndCallName: 'container.size()' (as a CXXMemberCallExpr)
///
/// Client code will need to make sure that:
/// - The containers on which 'size()' is called is the container indexed.
/// - The index variable is only used in overloaded operator[] or
/// container.at().
/// - The container's iterators would not be invalidated during the loop.
StatementMatcher makePseudoArrayLoopMatcher() {
// Test that the incoming type has a record declaration that has methods
// called 'begin' and 'end'. If the incoming type is const, then make sure
// these methods are also marked const.
//
// FIXME: To be completely thorough this matcher should also ensure the
// return type of begin/end is an iterator that dereferences to the same as
// what operator[] or at() returns. Such a test isn't likely to fail except
// for pathological cases.
//
// FIXME: Also, a record doesn't necessarily need begin() and end(). Free
// functions called begin() and end() taking the container as an argument
// are also allowed.
TypeMatcher RecordWithBeginEnd = qualType(anyOf(
qualType(
isConstQualified(),
hasUnqualifiedDesugaredType(recordType(hasDeclaration(cxxRecordDecl(
hasMethod(cxxMethodDecl(hasName("begin"), isConst())),
hasMethod(cxxMethodDecl(hasName("end"),
isConst())))) // hasDeclaration
))), // qualType
qualType(unless(isConstQualified()),
hasUnqualifiedDesugaredType(recordType(hasDeclaration(
cxxRecordDecl(hasMethod(hasName("begin")),
hasMethod(hasName("end"))))))) // qualType
));
StatementMatcher SizeCallMatcher = cxxMemberCallExpr(
argumentCountIs(0), callee(cxxMethodDecl(hasAnyName("size", "length"))),
on(anyOf(hasType(pointsTo(RecordWithBeginEnd)),
hasType(RecordWithBeginEnd))));
StatementMatcher EndInitMatcher =
expr(anyOf(ignoringParenImpCasts(expr(SizeCallMatcher).bind(EndCallName)),
explicitCastExpr(hasSourceExpression(ignoringParenImpCasts(
expr(SizeCallMatcher).bind(EndCallName))))));
DeclarationMatcher EndDeclMatcher =
varDecl(hasInitializer(EndInitMatcher)).bind(EndVarName);
StatementMatcher IndexBoundMatcher =
expr(anyOf(ignoringParenImpCasts(
declRefExpr(to(varDecl(equalsBoundNode(EndVarName))))),
EndInitMatcher));
return forStmt(unless(isInTemplateInstantiation()),
hasLoopInit(
anyOf(declStmt(declCountIs(2),
containsDeclaration(0, initToZeroMatcher()),
containsDeclaration(1, EndDeclMatcher)),
declStmt(hasSingleDecl(initToZeroMatcher())))),
hasCondition(arrayConditionMatcher(IndexBoundMatcher)),
hasIncrement(
unaryOperator(hasOperatorName("++"),
hasUnaryOperand(incrementVarMatcher()))))
.bind(LoopNamePseudoArray);
}
/// Determine whether Init appears to be an initializing an iterator.
///
/// If it is, returns the object whose begin() or end() method is called, and
/// the output parameter isArrow is set to indicate whether the initialization
/// is called via . or ->.
static const Expr *getContainerFromBeginEndCall(const Expr *Init, bool IsBegin,
bool *IsArrow, bool IsReverse) {
// FIXME: Maybe allow declaration/initialization outside of the for loop.
const auto *TheCall = dyn_cast_or_null<CXXMemberCallExpr>(
digThroughConstructorsConversions(Init));
if (!TheCall || TheCall->getNumArgs() != 0)
return nullptr;
const auto *Member = dyn_cast<MemberExpr>(TheCall->getCallee());
if (!Member)
return nullptr;
StringRef Name = Member->getMemberDecl()->getName();
if (!Name.consume_back(IsBegin ? "begin" : "end"))
return nullptr;
if (IsReverse && !Name.consume_back("r"))
return nullptr;
if (!Name.empty() && !Name.equals("c"))
return nullptr;
const Expr *SourceExpr = Member->getBase();
if (!SourceExpr)
return nullptr;
*IsArrow = Member->isArrow();
return SourceExpr;
}
/// Determines the container whose begin() and end() functions are called
/// for an iterator-based loop.
///
/// BeginExpr must be a member call to a function named "begin()", and EndExpr
/// must be a member.
static const Expr *findContainer(ASTContext *Context, const Expr *BeginExpr,
const Expr *EndExpr,
bool *ContainerNeedsDereference,
bool IsReverse) {
// Now that we know the loop variable and test expression, make sure they are
// valid.
bool BeginIsArrow = false;
bool EndIsArrow = false;
const Expr *BeginContainerExpr = getContainerFromBeginEndCall(
BeginExpr, /*IsBegin=*/true, &BeginIsArrow, IsReverse);
if (!BeginContainerExpr)
return nullptr;
const Expr *EndContainerExpr = getContainerFromBeginEndCall(
EndExpr, /*IsBegin=*/false, &EndIsArrow, IsReverse);
// Disallow loops that try evil things like this (note the dot and arrow):
// for (IteratorType It = Obj.begin(), E = Obj->end(); It != E; ++It) { }
if (!EndContainerExpr || BeginIsArrow != EndIsArrow ||
!areSameExpr(Context, EndContainerExpr, BeginContainerExpr))
return nullptr;
*ContainerNeedsDereference = BeginIsArrow;
return BeginContainerExpr;
}
/// Obtain the original source code text from a SourceRange.
static StringRef getStringFromRange(SourceManager &SourceMgr,
const LangOptions &LangOpts,
SourceRange Range) {
if (SourceMgr.getFileID(Range.getBegin()) !=
SourceMgr.getFileID(Range.getEnd())) {
return StringRef(); // Empty string.
}
return Lexer::getSourceText(CharSourceRange(Range, true), SourceMgr,
LangOpts);
}
/// If the given expression is actually a DeclRefExpr or a MemberExpr,
/// find and return the underlying ValueDecl; otherwise, return NULL.
static const ValueDecl *getReferencedVariable(const Expr *E) {
if (const DeclRefExpr *DRE = getDeclRef(E))
return dyn_cast<VarDecl>(DRE->getDecl());
if (const auto *Mem = dyn_cast<MemberExpr>(E->IgnoreParenImpCasts()))
return dyn_cast<FieldDecl>(Mem->getMemberDecl());
return nullptr;
}
/// Returns true when the given expression is a member expression
/// whose base is `this` (implicitly or not).
static bool isDirectMemberExpr(const Expr *E) {
if (const auto *Member = dyn_cast<MemberExpr>(E->IgnoreParenImpCasts()))
return isa<CXXThisExpr>(Member->getBase()->IgnoreParenImpCasts());
return false;
}
/// Given an expression that represents an usage of an element from the
/// containter that we are iterating over, returns false when it can be
/// guaranteed this element cannot be modified as a result of this usage.
static bool canBeModified(ASTContext *Context, const Expr *E) {
if (E->getType().isConstQualified())
return false;
auto Parents = Context->getParents(*E);
if (Parents.size() != 1)
return true;
if (const auto *Cast = Parents[0].get<ImplicitCastExpr>()) {
if ((Cast->getCastKind() == CK_NoOp &&
Context->hasSameType(Cast->getType(), E->getType().withConst())) ||
(Cast->getCastKind() == CK_LValueToRValue &&
!Cast->getType().isNull() && Cast->getType()->isFundamentalType()))
return false;
}
// FIXME: Make this function more generic.
return true;
}
/// Returns true when it can be guaranteed that the elements of the
/// container are not being modified.
static bool usagesAreConst(ASTContext *Context, const UsageResult &Usages) {
for (const Usage &U : Usages) {
// Lambda captures are just redeclarations (VarDecl) of the same variable,
// not expressions. If we want to know if a variable that is captured by
// reference can be modified in an usage inside the lambda's body, we need
// to find the expression corresponding to that particular usage, later in
// this loop.
if (U.Kind != Usage::UK_CaptureByCopy && U.Kind != Usage::UK_CaptureByRef &&
canBeModified(Context, U.Expression))
return false;
}
return true;
}
/// Returns true if the elements of the container are never accessed
/// by reference.
static bool usagesReturnRValues(const UsageResult &Usages) {
for (const auto &U : Usages) {
if (U.Expression && !U.Expression->isPRValue())
return false;
}
return true;
}
/// Returns true if the container is const-qualified.
static bool containerIsConst(const Expr *ContainerExpr, bool Dereference) {
if (const auto *VDec = getReferencedVariable(ContainerExpr)) {
QualType CType = VDec->getType();
if (Dereference) {
if (!CType->isPointerType())
return false;
CType = CType->getPointeeType();
}
// If VDec is a reference to a container, Dereference is false,
// but we still need to check the const-ness of the underlying container
// type.
CType = CType.getNonReferenceType();
return CType.isConstQualified();
}
return false;
}
LoopConvertCheck::RangeDescriptor::RangeDescriptor()
: ContainerNeedsDereference(false), DerefByConstRef(false),
DerefByValue(false), NeedsReverseCall(false) {}
LoopConvertCheck::LoopConvertCheck(StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context), TUInfo(new TUTrackingInfo),
MaxCopySize(Options.get("MaxCopySize", 16ULL)),
MinConfidence(Options.get("MinConfidence", Confidence::CL_Reasonable)),
NamingStyle(Options.get("NamingStyle", VariableNamer::NS_CamelCase)),
Inserter(Options.getLocalOrGlobal("IncludeStyle",
utils::IncludeSorter::IS_LLVM),
areDiagsSelfContained()),
UseCxx20IfAvailable(Options.get("UseCxx20ReverseRanges", true)),
ReverseFunction(Options.get("MakeReverseRangeFunction", "")),
ReverseHeader(Options.get("MakeReverseRangeHeader", "")) {
if (ReverseFunction.empty() && !ReverseHeader.empty()) {
configurationDiag(
"modernize-loop-convert: 'MakeReverseRangeHeader' is set but "
"'MakeReverseRangeFunction' is not, disabling reverse loop "
"transformation");
UseReverseRanges = false;
} else if (ReverseFunction.empty()) {
UseReverseRanges = UseCxx20IfAvailable && getLangOpts().CPlusPlus20;
} else {
UseReverseRanges = true;
}
}
void LoopConvertCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "MaxCopySize", MaxCopySize);
Options.store(Opts, "MinConfidence", MinConfidence);
Options.store(Opts, "NamingStyle", NamingStyle);
Options.store(Opts, "IncludeStyle", Inserter.getStyle());
Options.store(Opts, "UseCxx20ReverseRanges", UseCxx20IfAvailable);
Options.store(Opts, "MakeReverseRangeFunction", ReverseFunction);
Options.store(Opts, "MakeReverseRangeHeader", ReverseHeader);
}
void LoopConvertCheck::registerPPCallbacks(const SourceManager &SM,
Preprocessor *PP,
Preprocessor *ModuleExpanderPP) {
Inserter.registerPreprocessor(PP);
}
void LoopConvertCheck::registerMatchers(MatchFinder *Finder) {
Finder->addMatcher(traverse(TK_AsIs, makeArrayLoopMatcher()), this);
Finder->addMatcher(traverse(TK_AsIs, makeIteratorLoopMatcher(false)), this);
Finder->addMatcher(traverse(TK_AsIs, makePseudoArrayLoopMatcher()), this);
if (UseReverseRanges)
Finder->addMatcher(traverse(TK_AsIs, makeIteratorLoopMatcher(true)), this);
}
/// Given the range of a single declaration, such as:
/// \code
/// unsigned &ThisIsADeclarationThatCanSpanSeveralLinesOfCode =
/// InitializationValues[I];
/// next_instruction;
/// \endcode
/// Finds the range that has to be erased to remove this declaration without
/// leaving empty lines, by extending the range until the beginning of the
/// next instruction.
///
/// We need to delete a potential newline after the deleted alias, as
/// clang-format will leave empty lines untouched. For all other formatting we
/// rely on clang-format to fix it.
void LoopConvertCheck::getAliasRange(SourceManager &SM, SourceRange &Range) {
bool Invalid = false;
const char *TextAfter =
SM.getCharacterData(Range.getEnd().getLocWithOffset(1), &Invalid);
if (Invalid)
return;
unsigned Offset = std::strspn(TextAfter, " \t\r\n");
Range =
SourceRange(Range.getBegin(), Range.getEnd().getLocWithOffset(Offset));
}
/// Computes the changes needed to convert a given for loop, and
/// applies them.
void LoopConvertCheck::doConversion(
ASTContext *Context, const VarDecl *IndexVar,
const ValueDecl *MaybeContainer, const UsageResult &Usages,
const DeclStmt *AliasDecl, bool AliasUseRequired, bool AliasFromForInit,
const ForStmt *Loop, RangeDescriptor Descriptor) {
std::string VarName;
bool VarNameFromAlias = (Usages.size() == 1) && AliasDecl;
bool AliasVarIsRef = false;
bool CanCopy = true;
std::vector<FixItHint> FixIts;
if (VarNameFromAlias) {
const auto *AliasVar = cast<VarDecl>(AliasDecl->getSingleDecl());
VarName = AliasVar->getName().str();
// Use the type of the alias if it's not the same
QualType AliasVarType = AliasVar->getType();
assert(!AliasVarType.isNull() && "Type in VarDecl is null");
if (AliasVarType->isReferenceType()) {
AliasVarType = AliasVarType.getNonReferenceType();
AliasVarIsRef = true;
}
if (Descriptor.ElemType.isNull() ||
!Context->hasSameUnqualifiedType(AliasVarType, Descriptor.ElemType))
Descriptor.ElemType = AliasVarType;
// We keep along the entire DeclStmt to keep the correct range here.
SourceRange ReplaceRange = AliasDecl->getSourceRange();
std::string ReplacementText;
if (AliasUseRequired) {
ReplacementText = VarName;
} else if (AliasFromForInit) {
// FIXME: Clang includes the location of the ';' but only for DeclStmt's
// in a for loop's init clause. Need to put this ';' back while removing
// the declaration of the alias variable. This is probably a bug.
ReplacementText = ";";
} else {
// Avoid leaving empty lines or trailing whitespaces.
getAliasRange(Context->getSourceManager(), ReplaceRange);
}
FixIts.push_back(FixItHint::CreateReplacement(
CharSourceRange::getTokenRange(ReplaceRange), ReplacementText));
// No further replacements are made to the loop, since the iterator or index
// was used exactly once - in the initialization of AliasVar.
} else {
VariableNamer Namer(&TUInfo->getGeneratedDecls(),
&TUInfo->getParentFinder().getStmtToParentStmtMap(),
Loop, IndexVar, MaybeContainer, Context, NamingStyle);
VarName = Namer.createIndexName();
// First, replace all usages of the array subscript expression with our new
// variable.
for (const auto &Usage : Usages) {
std::string ReplaceText;
SourceRange Range = Usage.Range;
if (Usage.Expression) {
// If this is an access to a member through the arrow operator, after
// the replacement it must be accessed through the '.' operator.
ReplaceText = Usage.Kind == Usage::UK_MemberThroughArrow ? VarName + "."
: VarName;
auto Parents = Context->getParents(*Usage.Expression);
if (Parents.size() == 1) {
if (const auto *Paren = Parents[0].get<ParenExpr>()) {
// Usage.Expression will be replaced with the new index variable,
// and parenthesis around a simple DeclRefExpr can always be
// removed.
Range = Paren->getSourceRange();
} else if (const auto *UOP = Parents[0].get<UnaryOperator>()) {
// If we are taking the address of the loop variable, then we must
// not use a copy, as it would mean taking the address of the loop's
// local index instead.
// FIXME: This won't catch cases where the address is taken outside
// of the loop's body (for instance, in a function that got the
// loop's index as a const reference parameter), or where we take
// the address of a member (like "&Arr[i].A.B.C").
if (UOP->getOpcode() == UO_AddrOf)
CanCopy = false;
}
}
} else {
// The Usage expression is only null in case of lambda captures (which
// are VarDecl). If the index is captured by value, add '&' to capture
// by reference instead.
ReplaceText =
Usage.Kind == Usage::UK_CaptureByCopy ? "&" + VarName : VarName;
}
TUInfo->getReplacedVars().insert(std::make_pair(Loop, IndexVar));
FixIts.push_back(FixItHint::CreateReplacement(
CharSourceRange::getTokenRange(Range), ReplaceText));
}
}
// Now, we need to construct the new range expression.
SourceRange ParenRange(Loop->getLParenLoc(), Loop->getRParenLoc());
QualType Type = Context->getAutoDeductType();
if (!Descriptor.ElemType.isNull() && Descriptor.ElemType->isFundamentalType())
Type = Descriptor.ElemType.getUnqualifiedType();
Type = Type.getDesugaredType(*Context);
// If the new variable name is from the aliased variable, then the reference
// type for the new variable should only be used if the aliased variable was
// declared as a reference.
bool IsCheapToCopy =
!Descriptor.ElemType.isNull() &&
Descriptor.ElemType.isTriviallyCopyableType(*Context) &&
// TypeInfo::Width is in bits.
Context->getTypeInfo(Descriptor.ElemType).Width <= 8 * MaxCopySize;
bool UseCopy = CanCopy && ((VarNameFromAlias && !AliasVarIsRef) ||
(Descriptor.DerefByConstRef && IsCheapToCopy));
if (!UseCopy) {
if (Descriptor.DerefByConstRef) {
Type = Context->getLValueReferenceType(Context->getConstType(Type));
} else if (Descriptor.DerefByValue) {
if (!IsCheapToCopy)
Type = Context->getRValueReferenceType(Type);
} else {
Type = Context->getLValueReferenceType(Type);
}
}
SmallString<128> Range;
llvm::raw_svector_ostream Output(Range);
Output << '(';
Type.print(Output, getLangOpts());
Output << ' ' << VarName << " : ";
if (Descriptor.NeedsReverseCall)
Output << getReverseFunction() << '(';
if (Descriptor.ContainerNeedsDereference)
Output << '*';
Output << Descriptor.ContainerString;
if (Descriptor.NeedsReverseCall)
Output << "))";
else
Output << ')';
FixIts.push_back(FixItHint::CreateReplacement(
CharSourceRange::getTokenRange(ParenRange), Range));
if (Descriptor.NeedsReverseCall && !getReverseHeader().empty()) {
if (Optional<FixItHint> Insertion = Inserter.createIncludeInsertion(
Context->getSourceManager().getFileID(Loop->getBeginLoc()),
getReverseHeader()))
FixIts.push_back(*Insertion);
}
diag(Loop->getForLoc(), "use range-based for loop instead") << FixIts;
TUInfo->getGeneratedDecls().insert(make_pair(Loop, VarName));
}
/// Returns a string which refers to the container iterated over.
StringRef LoopConvertCheck::getContainerString(ASTContext *Context,
const ForStmt *Loop,
const Expr *ContainerExpr) {
StringRef ContainerString;
ContainerExpr = ContainerExpr->IgnoreParenImpCasts();
if (isa<CXXThisExpr>(ContainerExpr)) {
ContainerString = "this";
} else {
// For CXXOperatorCallExpr such as vector_ptr->size() we want the class
// object vector_ptr, but for vector[2] we need the whole expression.
if (const auto* E = dyn_cast<CXXOperatorCallExpr>(ContainerExpr))
if (E->getOperator() != OO_Subscript)
ContainerExpr = E->getArg(0);
ContainerString =
getStringFromRange(Context->getSourceManager(), Context->getLangOpts(),
ContainerExpr->getSourceRange());
}
return ContainerString;
}
/// Determines what kind of 'auto' must be used after converting a for
/// loop that iterates over an array or pseudoarray.
void LoopConvertCheck::getArrayLoopQualifiers(ASTContext *Context,
const BoundNodes &Nodes,
const Expr *ContainerExpr,
const UsageResult &Usages,
RangeDescriptor &Descriptor) {
// On arrays and pseudoarrays, we must figure out the qualifiers from the
// usages.
if (usagesAreConst(Context, Usages) ||
containerIsConst(ContainerExpr, Descriptor.ContainerNeedsDereference)) {
Descriptor.DerefByConstRef = true;
}
if (usagesReturnRValues(Usages)) {
// If the index usages (dereference, subscript, at, ...) return rvalues,
// then we should not use a reference, because we need to keep the code
// correct if it mutates the returned objects.
Descriptor.DerefByValue = true;
}
// Try to find the type of the elements on the container, to check if
// they are trivially copyable.
for (const Usage &U : Usages) {
if (!U.Expression || U.Expression->getType().isNull())
continue;
QualType Type = U.Expression->getType().getCanonicalType();
if (U.Kind == Usage::UK_MemberThroughArrow) {
if (!Type->isPointerType()) {
continue;
}
Type = Type->getPointeeType();
}
Descriptor.ElemType = Type;
}
}
/// Determines what kind of 'auto' must be used after converting an
/// iterator based for loop.
void LoopConvertCheck::getIteratorLoopQualifiers(ASTContext *Context,
const BoundNodes &Nodes,
RangeDescriptor &Descriptor) {
// The matchers for iterator loops provide bound nodes to obtain this
// information.
const auto *InitVar = Nodes.getNodeAs<VarDecl>(InitVarName);
QualType CanonicalInitVarType = InitVar->getType().getCanonicalType();
const auto *DerefByValueType =
Nodes.getNodeAs<QualType>(DerefByValueResultName);
Descriptor.DerefByValue = DerefByValueType;
if (Descriptor.DerefByValue) {
// If the dereference operator returns by value then test for the
// canonical const qualification of the init variable type.
Descriptor.DerefByConstRef = CanonicalInitVarType.isConstQualified();
Descriptor.ElemType = *DerefByValueType;
} else {
if (const auto *DerefType =
Nodes.getNodeAs<QualType>(DerefByRefResultName)) {
// A node will only be bound with DerefByRefResultName if we're dealing
// with a user-defined iterator type. Test the const qualification of
// the reference type.
auto ValueType = DerefType->getNonReferenceType();
Descriptor.DerefByConstRef = ValueType.isConstQualified();
Descriptor.ElemType = ValueType;
} else {
// By nature of the matcher this case is triggered only for built-in
// iterator types (i.e. pointers).
assert(isa<PointerType>(CanonicalInitVarType) &&
"Non-class iterator type is not a pointer type");
// We test for const qualification of the pointed-at type.
Descriptor.DerefByConstRef =
CanonicalInitVarType->getPointeeType().isConstQualified();
Descriptor.ElemType = CanonicalInitVarType->getPointeeType();
}
}
}
/// Determines the parameters needed to build the range replacement.
void LoopConvertCheck::determineRangeDescriptor(
ASTContext *Context, const BoundNodes &Nodes, const ForStmt *Loop,
LoopFixerKind FixerKind, const Expr *ContainerExpr,
const UsageResult &Usages, RangeDescriptor &Descriptor) {
Descriptor.ContainerString =
std::string(getContainerString(Context, Loop, ContainerExpr));
Descriptor.NeedsReverseCall = (FixerKind == LFK_ReverseIterator);
if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator)
getIteratorLoopQualifiers(Context, Nodes, Descriptor);
else
getArrayLoopQualifiers(Context, Nodes, ContainerExpr, Usages, Descriptor);
}
/// Check some of the conditions that must be met for the loop to be
/// convertible.
bool LoopConvertCheck::isConvertible(ASTContext *Context,
const ast_matchers::BoundNodes &Nodes,
const ForStmt *Loop,
LoopFixerKind FixerKind) {
// In self contained diagnosics mode we don't want dependancies on other
// loops, otherwise, If we already modified the range of this for loop, don't
// do any further updates on this iteration.
if (areDiagsSelfContained())
TUInfo = std::make_unique<TUTrackingInfo>();
else if (TUInfo->getReplacedVars().count(Loop))
return false;
// Check that we have exactly one index variable and at most one end variable.
const auto *InitVar = Nodes.getNodeAs<VarDecl>(InitVarName);
// FIXME: Try to put most of this logic inside a matcher.
if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator) {
QualType InitVarType = InitVar->getType();
QualType CanonicalInitVarType = InitVarType.getCanonicalType();
const auto *BeginCall = Nodes.getNodeAs<CXXMemberCallExpr>(BeginCallName);
assert(BeginCall && "Bad Callback. No begin call expression");
QualType CanonicalBeginType =
BeginCall->getMethodDecl()->getReturnType().getCanonicalType();
if (CanonicalBeginType->isPointerType() &&
CanonicalInitVarType->isPointerType()) {
// If the initializer and the variable are both pointers check if the
// un-qualified pointee types match, otherwise we don't use auto.
if (!Context->hasSameUnqualifiedType(
CanonicalBeginType->getPointeeType(),
CanonicalInitVarType->getPointeeType()))
return false;
}
} else if (FixerKind == LFK_PseudoArray) {
// This call is required to obtain the container.
const auto *EndCall = Nodes.getNodeAs<CXXMemberCallExpr>(EndCallName);
if (!EndCall || !isa<MemberExpr>(EndCall->getCallee()))
return false;
}
return true;
}
void LoopConvertCheck::check(const MatchFinder::MatchResult &Result) {
const BoundNodes &Nodes = Result.Nodes;
Confidence ConfidenceLevel(Confidence::CL_Safe);
ASTContext *Context = Result.Context;
const ForStmt *Loop;
LoopFixerKind FixerKind;
RangeDescriptor Descriptor;
if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameArray))) {
FixerKind = LFK_Array;
} else if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameIterator))) {
FixerKind = LFK_Iterator;
} else if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameReverseIterator))) {
FixerKind = LFK_ReverseIterator;
} else {
Loop = Nodes.getNodeAs<ForStmt>(LoopNamePseudoArray);
assert(Loop && "Bad Callback. No for statement");
FixerKind = LFK_PseudoArray;
}
if (!isConvertible(Context, Nodes, Loop, FixerKind))
return;
const auto *LoopVar = Nodes.getNodeAs<VarDecl>(InitVarName);
const auto *EndVar = Nodes.getNodeAs<VarDecl>(EndVarName);
// If the loop calls end()/size() after each iteration, lower our confidence
// level.
if (FixerKind != LFK_Array && !EndVar)
ConfidenceLevel.lowerTo(Confidence::CL_Reasonable);
// If the end comparison isn't a variable, we can try to work with the
// expression the loop variable is being tested against instead.
const auto *EndCall = Nodes.getNodeAs<CXXMemberCallExpr>(EndCallName);
const auto *BoundExpr = Nodes.getNodeAs<Expr>(ConditionBoundName);
// Find container expression of iterators and pseudoarrays, and determine if
// this expression needs to be dereferenced to obtain the container.
// With array loops, the container is often discovered during the
// ForLoopIndexUseVisitor traversal.
const Expr *ContainerExpr = nullptr;
if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator) {
ContainerExpr = findContainer(
Context, LoopVar->getInit(), EndVar ? EndVar->getInit() : EndCall,
&Descriptor.ContainerNeedsDereference,
/*IsReverse=*/FixerKind == LFK_ReverseIterator);
} else if (FixerKind == LFK_PseudoArray) {
ContainerExpr = EndCall->getImplicitObjectArgument();
Descriptor.ContainerNeedsDereference =
dyn_cast<MemberExpr>(EndCall->getCallee())->isArrow();
}
// We must know the container or an array length bound.
if (!ContainerExpr && !BoundExpr)
return;
ForLoopIndexUseVisitor Finder(Context, LoopVar, EndVar, ContainerExpr,
BoundExpr,
Descriptor.ContainerNeedsDereference);
// Find expressions and variables on which the container depends.
if (ContainerExpr) {
ComponentFinderASTVisitor ComponentFinder;
ComponentFinder.findExprComponents(ContainerExpr->IgnoreParenImpCasts());
Finder.addComponents(ComponentFinder.getComponents());
}
// Find usages of the loop index. If they are not used in a convertible way,
// stop here.
if (!Finder.findAndVerifyUsages(Loop->getBody()))
return;
ConfidenceLevel.lowerTo(Finder.getConfidenceLevel());
// Obtain the container expression, if we don't have it yet.
if (FixerKind == LFK_Array) {
ContainerExpr = Finder.getContainerIndexed()->IgnoreParenImpCasts();
// Very few loops are over expressions that generate arrays rather than
// array variables. Consider loops over arrays that aren't just represented
// by a variable to be risky conversions.
if (!getReferencedVariable(ContainerExpr) &&
!isDirectMemberExpr(ContainerExpr))
ConfidenceLevel.lowerTo(Confidence::CL_Risky);
}
// Find out which qualifiers we have to use in the loop range.
TraversalKindScope RAII(*Context, TK_AsIs);
const UsageResult &Usages = Finder.getUsages();
determineRangeDescriptor(Context, Nodes, Loop, FixerKind, ContainerExpr,
Usages, Descriptor);
// Ensure that we do not try to move an expression dependent on a local
// variable declared inside the loop outside of it.
// FIXME: Determine when the external dependency isn't an expression converted
// by another loop.
TUInfo->getParentFinder().gatherAncestors(*Context);
DependencyFinderASTVisitor DependencyFinder(
&TUInfo->getParentFinder().getStmtToParentStmtMap(),
&TUInfo->getParentFinder().getDeclToParentStmtMap(),
&TUInfo->getReplacedVars(), Loop);
if (DependencyFinder.dependsOnInsideVariable(ContainerExpr) ||
Descriptor.ContainerString.empty() || Usages.empty() ||
ConfidenceLevel.getLevel() < MinConfidence)
return;
doConversion(Context, LoopVar, getReferencedVariable(ContainerExpr), Usages,
Finder.getAliasDecl(), Finder.aliasUseRequired(),
Finder.aliasFromForInit(), Loop, Descriptor);
}
llvm::StringRef LoopConvertCheck::getReverseFunction() const {
if (!ReverseFunction.empty())
return ReverseFunction;
if (UseReverseRanges)
return "std::ranges::reverse_view";
return "";
}
llvm::StringRef LoopConvertCheck::getReverseHeader() const {
if (!ReverseHeader.empty())
return ReverseHeader;
if (UseReverseRanges && ReverseFunction.empty()) {
return "<ranges>";
}
return "";
}
} // namespace modernize
} // namespace tidy
} // namespace clang
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