//===-- lib/Semantics/pointer-assignment.cpp ------------------------------===//
//
// 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 "pointer-assignment.h"
#include "definable.h"
#include "flang/Common/idioms.h"
#include "flang/Common/restorer.h"
#include "flang/Common/template.h"
#include "flang/Evaluate/characteristics.h"
#include "flang/Evaluate/expression.h"
#include "flang/Evaluate/fold.h"
#include "flang/Evaluate/tools.h"
#include "flang/Parser/message.h"
#include "flang/Parser/parse-tree-visitor.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Semantics/expression.h"
#include "flang/Semantics/symbol.h"
#include "flang/Semantics/tools.h"
#include "llvm/Support/raw_ostream.h"
#include <optional>
#include <set>
#include <string>
#include <type_traits>
// Semantic checks for pointer assignment.
namespace Fortran::semantics {
using namespace parser::literals;
using evaluate::characteristics::DummyDataObject;
using evaluate::characteristics::FunctionResult;
using evaluate::characteristics::Procedure;
using evaluate::characteristics::TypeAndShape;
using parser::MessageFixedText;
using parser::MessageFormattedText;
class PointerAssignmentChecker {
public:
PointerAssignmentChecker(SemanticsContext &context, const Scope &scope,
parser::CharBlock source, const std::string &description)
: context_{context}, scope_{scope}, source_{source}, description_{
description} {}
PointerAssignmentChecker(
SemanticsContext &context, const Scope &scope, const Symbol &lhs)
: context_{context}, scope_{scope}, source_{lhs.name()},
description_{"pointer '"s + lhs.name().ToString() + '\''}, lhs_{&lhs} {
set_lhsType(TypeAndShape::Characterize(lhs, foldingContext_));
set_isContiguous(lhs.attrs().test(Attr::CONTIGUOUS));
set_isVolatile(lhs.attrs().test(Attr::VOLATILE));
}
PointerAssignmentChecker &set_lhsType(std::optional<TypeAndShape> &&);
PointerAssignmentChecker &set_isContiguous(bool);
PointerAssignmentChecker &set_isVolatile(bool);
PointerAssignmentChecker &set_isBoundsRemapping(bool);
PointerAssignmentChecker &set_isAssumedRank(bool);
PointerAssignmentChecker &set_pointerComponentLHS(const Symbol *);
bool CheckLeftHandSide(const SomeExpr &);
bool Check(const SomeExpr &);
private:
bool CharacterizeProcedure();
template <typename T> bool Check(const T &);
template <typename T> bool Check(const evaluate::Expr<T> &);
template <typename T> bool Check(const evaluate::FunctionRef<T> &);
template <typename T> bool Check(const evaluate::Designator<T> &);
bool Check(const evaluate::NullPointer &);
bool Check(const evaluate::ProcedureDesignator &);
bool Check(const evaluate::ProcedureRef &);
// Target is a procedure
bool Check(parser::CharBlock rhsName, bool isCall,
const Procedure * = nullptr,
const evaluate::SpecificIntrinsic *specific = nullptr);
bool LhsOkForUnlimitedPoly() const;
template <typename... A> parser::Message *Say(A &&...);
SemanticsContext &context_;
evaluate::FoldingContext &foldingContext_{context_.foldingContext()};
const Scope &scope_;
const parser::CharBlock source_;
const std::string description_;
const Symbol *lhs_{nullptr};
std::optional<TypeAndShape> lhsType_;
std::optional<Procedure> procedure_;
bool characterizedProcedure_{false};
bool isContiguous_{false};
bool isVolatile_{false};
bool isBoundsRemapping_{false};
bool isAssumedRank_{false};
const Symbol *pointerComponentLHS_{nullptr};
};
PointerAssignmentChecker &PointerAssignmentChecker::set_lhsType(
std::optional<TypeAndShape> &&lhsType) {
lhsType_ = std::move(lhsType);
return *this;
}
PointerAssignmentChecker &PointerAssignmentChecker::set_isContiguous(
bool isContiguous) {
isContiguous_ = isContiguous;
return *this;
}
PointerAssignmentChecker &PointerAssignmentChecker::set_isVolatile(
bool isVolatile) {
isVolatile_ = isVolatile;
return *this;
}
PointerAssignmentChecker &PointerAssignmentChecker::set_isBoundsRemapping(
bool isBoundsRemapping) {
isBoundsRemapping_ = isBoundsRemapping;
return *this;
}
PointerAssignmentChecker &PointerAssignmentChecker::set_isAssumedRank(
bool isAssumedRank) {
isAssumedRank_ = isAssumedRank;
return *this;
}
PointerAssignmentChecker &PointerAssignmentChecker::set_pointerComponentLHS(
const Symbol *symbol) {
pointerComponentLHS_ = symbol;
return *this;
}
bool PointerAssignmentChecker::CharacterizeProcedure() {
if (!characterizedProcedure_) {
characterizedProcedure_ = true;
if (lhs_ && IsProcedure(*lhs_)) {
procedure_ = Procedure::Characterize(*lhs_, foldingContext_);
}
}
return procedure_.has_value();
}
bool PointerAssignmentChecker::CheckLeftHandSide(const SomeExpr &lhs) {
if (auto whyNot{WhyNotDefinable(foldingContext_.messages().at(), scope_,
DefinabilityFlags{DefinabilityFlag::PointerDefinition}, lhs)}) {
if (auto *msg{Say(
"The left-hand side of a pointer assignment is not definable"_err_en_US)}) {
msg->Attach(std::move(whyNot->set_severity(parser::Severity::Because)));
}
return false;
} else if (evaluate::IsAssumedRank(lhs)) {
Say("The left-hand side of a pointer assignment must not be an assumed-rank dummy argument"_err_en_US);
return false;
} else {
return true;
}
}
template <typename T> bool PointerAssignmentChecker::Check(const T &) {
// Catch-all case for really bad target expression
Say("Target associated with %s must be a designator or a call to a"
" pointer-valued function"_err_en_US,
description_);
return false;
}
template <typename T>
bool PointerAssignmentChecker::Check(const evaluate::Expr<T> &x) {
return common::visit([&](const auto &x) { return Check(x); }, x.u);
}
bool PointerAssignmentChecker::Check(const SomeExpr &rhs) {
if (HasVectorSubscript(rhs)) { // C1025
Say("An array section with a vector subscript may not be a pointer target"_err_en_US);
return false;
}
if (ExtractCoarrayRef(rhs)) { // C1026
Say("A coindexed object may not be a pointer target"_err_en_US);
return false;
}
if (!common::visit([&](const auto &x) { return Check(x); }, rhs.u)) {
return false;
}
if (IsNullPointer(rhs)) {
return true;
}
if (lhs_ && IsProcedure(*lhs_)) {
return true;
}
if (const auto *pureProc{FindPureProcedureContaining(scope_)}) {
if (pointerComponentLHS_) { // C1594(4) is a hard error
if (const Symbol * object{FindExternallyVisibleObject(rhs, *pureProc)}) {
if (auto *msg{Say(
"Externally visible object '%s' may not be associated with pointer component '%s' in a pure procedure"_err_en_US,
object->name(), pointerComponentLHS_->name())}) {
msg->Attach(object->name(), "Object declaration"_en_US)
.Attach(
pointerComponentLHS_->name(), "Pointer declaration"_en_US);
}
return false;
}
} else if (const Symbol * base{GetFirstSymbol(rhs)}) {
if (const char *why{WhyBaseObjectIsSuspicious(
base->GetUltimate(), scope_)}) { // C1594(3)
evaluate::SayWithDeclaration(foldingContext_.messages(), *base,
"A pure subprogram may not use '%s' as the target of pointer assignment because it is %s"_err_en_US,
base->name(), why);
return false;
}
}
}
if (isContiguous_) {
if (auto contiguous{evaluate::IsContiguous(rhs, foldingContext_)}) {
if (!*contiguous) {
Say("CONTIGUOUS pointer may not be associated with a discontiguous target"_err_en_US);
return false;
}
} else if (context_.ShouldWarn(
common::UsageWarning::PointerToPossibleNoncontiguous)) {
Say("Target of CONTIGUOUS pointer association is not known to be contiguous"_warn_en_US);
}
}
// Warn about undefinable data targets
if (context_.ShouldWarn(common::UsageWarning::PointerToUndefinable)) {
if (auto because{WhyNotDefinable(
foldingContext_.messages().at(), scope_, {}, rhs)}) {
if (auto *msg{
Say("Pointer target is not a definable variable"_warn_en_US)}) {
msg->Attach(
std::move(because->set_severity(parser::Severity::Because)));
}
return false;
}
}
return true;
}
bool PointerAssignmentChecker::Check(const evaluate::NullPointer &) {
return true; // P => NULL() without MOLD=; always OK
}
template <typename T>
bool PointerAssignmentChecker::Check(const evaluate::FunctionRef<T> &f) {
std::string funcName;
const auto *symbol{f.proc().GetSymbol()};
if (symbol) {
funcName = symbol->name().ToString();
} else if (const auto *intrinsic{f.proc().GetSpecificIntrinsic()}) {
funcName = intrinsic->name;
}
auto proc{
Procedure::Characterize(f.proc(), foldingContext_, /*emitError=*/true)};
if (!proc) {
return false;
}
std::optional<MessageFixedText> msg;
const auto &funcResult{proc->functionResult}; // C1025
if (!funcResult) {
msg = "%s is associated with the non-existent result of reference to"
" procedure"_err_en_US;
} else if (CharacterizeProcedure()) {
// Shouldn't be here in this function unless lhs is an object pointer.
msg = "Procedure %s is associated with the result of a reference to"
" function '%s' that does not return a procedure pointer"_err_en_US;
} else if (funcResult->IsProcedurePointer()) {
msg = "Object %s is associated with the result of a reference to"
" function '%s' that is a procedure pointer"_err_en_US;
} else if (!funcResult->attrs.test(FunctionResult::Attr::Pointer)) {
msg = "%s is associated with the result of a reference to function '%s'"
" that is a not a pointer"_err_en_US;
} else if (isContiguous_ &&
!funcResult->attrs.test(FunctionResult::Attr::Contiguous)) {
if (context_.ShouldWarn(
common::UsageWarning::PointerToPossibleNoncontiguous)) {
msg =
"CONTIGUOUS %s is associated with the result of reference to function '%s' that is not known to be contiguous"_warn_en_US;
}
} else if (lhsType_) {
const auto *frTypeAndShape{funcResult->GetTypeAndShape()};
CHECK(frTypeAndShape);
if (!lhsType_->IsCompatibleWith(foldingContext_.messages(), *frTypeAndShape,
"pointer", "function result",
/*omitShapeConformanceCheck=*/isBoundsRemapping_ || isAssumedRank_,
evaluate::CheckConformanceFlags::BothDeferredShape)) {
return false; // IsCompatibleWith() emitted message
}
}
if (msg) {
auto restorer{common::ScopedSet(lhs_, symbol)};
Say(*msg, description_, funcName);
return false;
}
return true;
}
template <typename T>
bool PointerAssignmentChecker::Check(const evaluate::Designator<T> &d) {
const Symbol *last{d.GetLastSymbol()};
const Symbol *base{d.GetBaseObject().symbol()};
if (!last || !base) {
// P => "character literal"(1:3)
Say("Pointer target is not a named entity"_err_en_US);
return false;
}
std::optional<std::variant<MessageFixedText, MessageFormattedText>> msg;
if (CharacterizeProcedure()) {
// Shouldn't be here in this function unless lhs is an object pointer.
msg = "In assignment to procedure %s, the target is not a procedure or"
" procedure pointer"_err_en_US;
} else if (!evaluate::GetLastTarget(GetSymbolVector(d))) { // C1025
msg = "In assignment to object %s, the target '%s' is not an object with"
" POINTER or TARGET attributes"_err_en_US;
} else if (auto rhsType{TypeAndShape::Characterize(d, foldingContext_)}) {
if (!lhsType_) {
msg = "%s associated with object '%s' with incompatible type or"
" shape"_err_en_US;
} else if (rhsType->corank() > 0 &&
(isVolatile_ != last->attrs().test(Attr::VOLATILE))) { // C1020
// TODO: what if A is VOLATILE in A%B%C? need a better test here
if (isVolatile_) {
msg = "Pointer may not be VOLATILE when target is a"
" non-VOLATILE coarray"_err_en_US;
} else {
msg = "Pointer must be VOLATILE when target is a"
" VOLATILE coarray"_err_en_US;
}
} else if (rhsType->type().IsUnlimitedPolymorphic()) {
if (!LhsOkForUnlimitedPoly()) {
msg = "Pointer type must be unlimited polymorphic or non-extensible"
" derived type when target is unlimited polymorphic"_err_en_US;
}
} else {
if (!lhsType_->type().IsTkLenCompatibleWith(rhsType->type())) {
msg = MessageFormattedText{
"Target type %s is not compatible with pointer type %s"_err_en_US,
rhsType->type().AsFortran(), lhsType_->type().AsFortran()};
} else if (!isBoundsRemapping_ &&
!lhsType_->attrs().test(TypeAndShape::Attr::AssumedRank)) {
int lhsRank{lhsType_->Rank()};
int rhsRank{rhsType->Rank()};
if (lhsRank != rhsRank) {
msg = MessageFormattedText{
"Pointer has rank %d but target has rank %d"_err_en_US, lhsRank,
rhsRank};
}
}
}
}
if (msg) {
auto restorer{common::ScopedSet(lhs_, last)};
if (auto *m{std::get_if<MessageFixedText>(&*msg)}) {
std::string buf;
llvm::raw_string_ostream ss{buf};
d.AsFortran(ss);
Say(*m, description_, ss.str());
} else {
Say(std::get<MessageFormattedText>(*msg));
}
return false;
} else {
context_.NoteDefinedSymbol(*base);
return true;
}
}
// Common handling for procedure pointer right-hand sides
bool PointerAssignmentChecker::Check(parser::CharBlock rhsName, bool isCall,
const Procedure *rhsProcedure,
const evaluate::SpecificIntrinsic *specific) {
std::string whyNot;
std::optional<std::string> warning;
CharacterizeProcedure();
if (std::optional<MessageFixedText> msg{evaluate::CheckProcCompatibility(
isCall, procedure_, rhsProcedure, specific, whyNot, warning,
/*ignoreImplicitVsExplicit=*/isCall)}) {
Say(std::move(*msg), description_, rhsName, whyNot);
return false;
}
if (context_.ShouldWarn(common::UsageWarning::ProcDummyArgShapes) &&
warning) {
Say("%s and %s may not be completely compatible procedures: %s"_warn_en_US,
description_, rhsName, std::move(*warning));
}
return true;
}
bool PointerAssignmentChecker::Check(const evaluate::ProcedureDesignator &d) {
const Symbol *symbol{d.GetSymbol()};
if (symbol) {
if (const auto *subp{
symbol->GetUltimate().detailsIf<SubprogramDetails>()}) {
if (subp->stmtFunction()) {
evaluate::SayWithDeclaration(foldingContext_.messages(), *symbol,
"Statement function '%s' may not be the target of a pointer assignment"_err_en_US,
symbol->name());
return false;
}
} else if (symbol->has<ProcBindingDetails>() &&
context_.ShouldWarn(common::LanguageFeature::BindingAsProcedure)) {
evaluate::SayWithDeclaration(foldingContext_.messages(), *symbol,
"Procedure binding '%s' used as target of a pointer assignment"_port_en_US,
symbol->name());
}
}
if (auto chars{
Procedure::Characterize(d, foldingContext_, /*emitError=*/true)}) {
// Disregard the elemental attribute of RHS intrinsics.
if (symbol && symbol->GetUltimate().attrs().test(Attr::INTRINSIC)) {
chars->attrs.reset(Procedure::Attr::Elemental);
}
return Check(d.GetName(), false, &*chars, d.GetSpecificIntrinsic());
} else {
return Check(d.GetName(), false);
}
}
bool PointerAssignmentChecker::Check(const evaluate::ProcedureRef &ref) {
auto chars{Procedure::Characterize(ref, foldingContext_)};
return Check(ref.proc().GetName(), true, common::GetPtrFromOptional(chars));
}
// The target can be unlimited polymorphic if the pointer is, or if it is
// a non-extensible derived type.
bool PointerAssignmentChecker::LhsOkForUnlimitedPoly() const {
const auto &type{lhsType_->type()};
if (type.category() != TypeCategory::Derived || type.IsAssumedType()) {
return false;
} else if (type.IsUnlimitedPolymorphic()) {
return true;
} else {
return !IsExtensibleType(&type.GetDerivedTypeSpec());
}
}
template <typename... A>
parser::Message *PointerAssignmentChecker::Say(A &&...x) {
auto *msg{foldingContext_.messages().Say(std::forward<A>(x)...)};
if (msg) {
if (lhs_) {
return evaluate::AttachDeclaration(msg, *lhs_);
}
if (!source_.empty()) {
msg->Attach(source_, "Declaration of %s"_en_US, description_);
}
}
return msg;
}
// Verify that any bounds on the LHS of a pointer assignment are valid.
// Return true if it is a bound-remapping so we can perform further checks.
static bool CheckPointerBounds(
evaluate::FoldingContext &context, const evaluate::Assignment &assignment) {
auto &messages{context.messages()};
const SomeExpr &lhs{assignment.lhs};
const SomeExpr &rhs{assignment.rhs};
bool isBoundsRemapping{false};
std::size_t numBounds{common::visit(
common::visitors{
[&](const evaluate::Assignment::BoundsSpec &bounds) {
return bounds.size();
},
[&](const evaluate::Assignment::BoundsRemapping &bounds) {
isBoundsRemapping = true;
evaluate::ExtentExpr lhsSizeExpr{1};
for (const auto &bound : bounds) {
lhsSizeExpr = std::move(lhsSizeExpr) *
(common::Clone(bound.second) - common::Clone(bound.first) +
evaluate::ExtentExpr{1});
}
if (std::optional<std::int64_t> lhsSize{evaluate::ToInt64(
evaluate::Fold(context, std::move(lhsSizeExpr)))}) {
if (auto shape{evaluate::GetShape(context, rhs)}) {
if (std::optional<std::int64_t> rhsSize{
evaluate::ToInt64(evaluate::Fold(
context, evaluate::GetSize(std::move(*shape))))}) {
if (*lhsSize > *rhsSize) {
messages.Say(
"Pointer bounds require %d elements but target has"
" only %d"_err_en_US,
*lhsSize, *rhsSize); // 10.2.2.3(9)
}
}
}
}
return bounds.size();
},
[](const auto &) -> std::size_t {
DIE("not valid for pointer assignment");
},
},
assignment.u)};
if (numBounds > 0) {
if (lhs.Rank() != static_cast<int>(numBounds)) {
messages.Say("Pointer '%s' has rank %d but the number of bounds specified"
" is %d"_err_en_US,
lhs.AsFortran(), lhs.Rank(), numBounds); // C1018
}
}
if (isBoundsRemapping && rhs.Rank() != 1 &&
!evaluate::IsSimplyContiguous(rhs, context)) {
messages.Say("Pointer bounds remapping target must have rank 1 or be"
" simply contiguous"_err_en_US); // 10.2.2.3(9)
}
return isBoundsRemapping;
}
bool CheckPointerAssignment(SemanticsContext &context,
const evaluate::Assignment &assignment, const Scope &scope) {
return CheckPointerAssignment(context, assignment.lhs, assignment.rhs, scope,
CheckPointerBounds(context.foldingContext(), assignment),
/*isAssumedRank=*/false);
}
bool CheckPointerAssignment(SemanticsContext &context, const SomeExpr &lhs,
const SomeExpr &rhs, const Scope &scope, bool isBoundsRemapping,
bool isAssumedRank) {
const Symbol *pointer{GetLastSymbol(lhs)};
if (!pointer) {
return false; // error was reported
}
PointerAssignmentChecker checker{context, scope, *pointer};
checker.set_isBoundsRemapping(isBoundsRemapping);
checker.set_isAssumedRank(isAssumedRank);
bool lhsOk{checker.CheckLeftHandSide(lhs)};
bool rhsOk{checker.Check(rhs)};
return lhsOk && rhsOk; // don't short-circuit
}
bool CheckStructConstructorPointerComponent(SemanticsContext &context,
const Symbol &lhs, const SomeExpr &rhs, const Scope &scope) {
return PointerAssignmentChecker{context, scope, lhs}
.set_pointerComponentLHS(&lhs)
.Check(rhs);
}
bool CheckPointerAssignment(SemanticsContext &context, parser::CharBlock source,
const std::string &description, const DummyDataObject &lhs,
const SomeExpr &rhs, const Scope &scope, bool isAssumedRank) {
return PointerAssignmentChecker{context, scope, source, description}
.set_lhsType(common::Clone(lhs.type))
.set_isContiguous(lhs.attrs.test(DummyDataObject::Attr::Contiguous))
.set_isVolatile(lhs.attrs.test(DummyDataObject::Attr::Volatile))
.set_isAssumedRank(isAssumedRank)
.Check(rhs);
}
bool CheckInitialDataPointerTarget(SemanticsContext &context,
const SomeExpr &pointer, const SomeExpr &init, const Scope &scope) {
return evaluate::IsInitialDataTarget(
init, &context.foldingContext().messages()) &&
CheckPointerAssignment(context, pointer, init, scope,
/*isBoundsRemapping=*/false,
/*isAssumedRank=*/false);
}
} // namespace Fortran::semantics
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