blob: afa15522127d30a3f2c278bef35e8666f89ac43e [file] [log] [blame]
//===-- lib/Semantics/pointer-assignment.cpp ------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "pointer-assignment.h"
#include "flang/Common/idioms.h"
#include "flang/Common/restorer.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 {
PointerAssignmentChecker(evaluate::FoldingContext &context,
parser::CharBlock source, const std::string &description)
: context_{context}, source_{source}, description_{description} {}
PointerAssignmentChecker(evaluate::FoldingContext &context, const Symbol &lhs)
: context_{context}, source_{},
description_{"pointer '"s + + '\''}, lhs_{&lhs} {
set_lhsType(TypeAndShape::Characterize(lhs, context));
if (IsProcedure(lhs)) {
procedure_ = Procedure::Characterize(lhs, context);
PointerAssignmentChecker &set_lhsType(std::optional<TypeAndShape> &&);
PointerAssignmentChecker &set_isContiguous(bool);
PointerAssignmentChecker &set_isVolatile(bool);
PointerAssignmentChecker &set_isBoundsRemapping(bool);
bool Check(const SomeExpr &);
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);
bool LhsOkForUnlimitedPoly() const;
template <typename... A> parser::Message *Say(A &&...);
evaluate::FoldingContext &context_;
const parser::CharBlock source_;
const std::string description_;
const Symbol *lhs_{nullptr};
std::optional<TypeAndShape> lhsType_;
std::optional<Procedure> procedure_;
bool isContiguous_{false};
bool isVolatile_{false};
bool isBoundsRemapping_{false};
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;
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,
return false;
template <typename T>
bool PointerAssignmentChecker::Check(const evaluate::Expr<T> &x) {
return std::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;
} else if (ExtractCoarrayRef(rhs)) { // C1026
Say("A coindexed object may not be a pointer target"_err_en_US);
return false;
} else {
return std::visit([&](const auto &x) { return Check(x); }, rhs.u);
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(), context_)};
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 (procedure_) {
// 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)) {
msg = "CONTIGUOUS %s is associated with the result of reference to"
" function '%s' that is not contiguous"_err_en_US;
} else if (lhsType_) {
const auto *frTypeAndShape{funcResult->GetTypeAndShape()};
if (!lhsType_->IsCompatibleWith(context_.messages(), *frTypeAndShape,
"pointer", "function result", false /*elemental*/,
evaluate::CheckConformanceFlags::BothDeferredShape)) {
msg = "%s is associated with the result of a reference to function '%s'"
" whose pointer result has an incompatible type or shape"_err_en_US;
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)
context_.messages().Say("Pointer target is not a named entity"_err_en_US);
return false;
std::optional<std::variant<MessageFixedText, MessageFormattedText>> msg;
if (procedure_) {
// 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, context_)}) {
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().IsTkCompatibleWith(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_) {
int lhsRank{evaluate::GetRank(lhsType_->shape())};
int rhsRank{evaluate::GetRank(rhsType->shape())};
if (lhsRank != rhsRank) {
msg = MessageFormattedText{
"Pointer has rank %d but target has rank %d"_err_en_US, lhsRank,
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};
Say(*m, description_, ss.str());
} else {
return false;
return true;
// Common handling for procedure pointer right-hand sides
bool PointerAssignmentChecker::Check(
parser::CharBlock rhsName, bool isCall, const Procedure *rhsProcedure) {
if (std::optional<MessageFixedText> msg{
evaluate::CheckProcCompatibility(isCall, procedure_, rhsProcedure)}) {
Say(std::move(*msg), description_, rhsName);
return false;
return true;
bool PointerAssignmentChecker::Check(const evaluate::ProcedureDesignator &d) {
if (auto chars{Procedure::Characterize(d, context_)}) {
return Check(d.GetName(), false, &*chars);
} else {
return Check(d.GetName(), false);
bool PointerAssignmentChecker::Check(const evaluate::ProcedureRef &ref) {
const Procedure *procedure{nullptr};
auto chars{Procedure::Characterize(ref, context_)};
if (chars) {
procedure = &*chars;
if (chars->functionResult) {
if (const auto *proc{chars->functionResult->IsProcedurePointer()}) {
procedure = proc;
return Check(ref.proc().GetName(), true, procedure);
// 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{context_.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{std::visit(
[&](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) +
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{
context, evaluate::GetSize(std::move(*shape))))}) {
if (*lhsSize > *rhsSize) {
"Pointer bounds require %d elements but target has"
" only %d"_err_en_US,
*lhsSize, *rhsSize); //
return bounds.size();
[](const auto &) -> std::size_t {
DIE("not valid for pointer assignment");
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); //
return isBoundsRemapping;
bool CheckPointerAssignment(
evaluate::FoldingContext &context, const evaluate::Assignment &assignment) {
return CheckPointerAssignment(context, assignment.lhs, assignment.rhs,
CheckPointerBounds(context, assignment));
bool CheckPointerAssignment(evaluate::FoldingContext &context,
const SomeExpr &lhs, const SomeExpr &rhs, bool isBoundsRemapping) {
const Symbol *pointer{GetLastSymbol(lhs)};
if (!pointer) {
return false; // error was reported
if (!IsPointer(*pointer)) {
evaluate::SayWithDeclaration(context.messages(), *pointer,
"'%s' is not a pointer"_err_en_US, pointer->name());
return false;
if (pointer->has<ProcEntityDetails>() && evaluate::ExtractCoarrayRef(lhs)) {
context.messages().Say( // C1027
"Procedure pointer may not be a coindexed object"_err_en_US);
return false;
return PointerAssignmentChecker{context, *pointer}
bool CheckPointerAssignment(
evaluate::FoldingContext &context, const Symbol &lhs, const SomeExpr &rhs) {
return PointerAssignmentChecker{context, lhs}.Check(rhs);
bool CheckPointerAssignment(evaluate::FoldingContext &context,
parser::CharBlock source, const std::string &description,
const DummyDataObject &lhs, const SomeExpr &rhs) {
return PointerAssignmentChecker{context, source, description}
bool CheckInitialTarget(evaluate::FoldingContext &context,
const SomeExpr &pointer, const SomeExpr &init) {
return evaluate::IsInitialDataTarget(init, &context.messages()) &&
CheckPointerAssignment(context, pointer, init);
} // namespace Fortran::semantics