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[flang] Catch attempts to subscribe empty arrays #108246

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Merged
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Sep 12, 2024
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[flang] Catch attempts to subscribe empty arrays #108246

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2 changes: 1 addition & 1 deletion flang/include/flang/Semantics/expression.h
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Original file line number Diff line number Diff line change
Expand Up @@ -331,7 +331,7 @@ class ExpressionAnalyzer {
const semantics::Scope &, bool C919bAlreadyEnforced = false);
MaybeExpr CompleteSubscripts(ArrayRef &&);
MaybeExpr ApplySubscripts(DataRef &&, std::vector<Subscript> &&);
void CheckConstantSubscripts(ArrayRef &);
void CheckSubscripts(ArrayRef &);
bool CheckRanks(const DataRef &); // Return false if error exists.
bool CheckPolymorphic(const DataRef &); // ditto
bool CheckDataRef(const DataRef &); // ditto
Expand Down
11 changes: 9 additions & 2 deletions flang/lib/Semantics/expression.cpp
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Expand Up @@ -298,7 +298,7 @@ MaybeExpr ExpressionAnalyzer::CompleteSubscripts(ArrayRef &&ref) {
// Subscripts of named constants are checked in folding.
// Subscripts of DATA statement objects are checked in data statement
// conversion to initializers.
CheckConstantSubscripts(ref);
CheckSubscripts(ref);
}
return Designate(DataRef{std::move(ref)});
}
Expand Down Expand Up @@ -326,7 +326,7 @@ MaybeExpr ExpressionAnalyzer::ApplySubscripts(
std::move(dataRef.u));
}

void ExpressionAnalyzer::CheckConstantSubscripts(ArrayRef &ref) {
void ExpressionAnalyzer::CheckSubscripts(ArrayRef &ref) {
// Fold subscript expressions and check for an empty triplet.
const Symbol &arraySymbol{ref.base().GetLastSymbol()};
Shape lb{GetLBOUNDs(foldingContext_, NamedEntity{arraySymbol})};
Expand Down Expand Up @@ -390,6 +390,13 @@ void ExpressionAnalyzer::CheckConstantSubscripts(ArrayRef &ref) {
for (Subscript &ss : ref.subscript()) {
auto dimLB{ToInt64(lb[dim])};
auto dimUB{ToInt64(ub[dim])};
if (dimUB && dimLB && *dimUB < *dimLB) {
AttachDeclaration(
Say("Empty array dimension %d cannot be subscripted as an element or non-empty array section"_err_en_US,
dim + 1),
arraySymbol);
break;
}
std::optional<ConstantSubscript> val[2];
int vals{0};
if (auto *triplet{std::get_if<Triplet>(&ss.u)}) {
Expand Down
8 changes: 7 additions & 1 deletion flang/test/Semantics/expr-errors06.f90
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@@ -1,7 +1,7 @@
! RUN: %python %S/test_errors.py %s %flang_fc1 -Werror
! Check out-of-range subscripts
subroutine subr(da)
real a(10), da(2,1)
real a(10), da(2,1), empty(1:0,1)
integer, parameter :: n(2) = [1, 2]
integer unknown
!ERROR: DATA statement designator 'a(0_8)' is out of range
Expand Down Expand Up @@ -39,4 +39,10 @@ subroutine subr(da)
print *, da(1,0)
!WARNING: Subscript 2 is greater than upper bound 1 for dimension 2 of array
print *, da(1,2)
print *, empty([(j,j=1,0)],1) ! ok
print *, empty(1:0,1) ! ok
print *, empty(:,1) ! ok
print *, empty(i:j,k) ! ok
!ERROR: Empty array dimension 1 cannot be subscripted as an element or non-empty array section
print *, empty(i,1)
end
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