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[flang] Don't allow non-standard data conversions of potentially abse… (#87391)

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…nt arguments

Arguments to the intrinsic functions MAX and MIN after the first two are
optional. When these actual arguments might not be present at run time,
emit a compilation time error if they require data conversion (a
non-standard but nearly universal language extension); such a conversion
would crash if the argument was absent.

Other compilers either disallow data conversions entirely on MAX/MIN or
crash at run time if a converted argument is absent.

Fixes https://github.com/llvm/llvm-project/issues/87046.
This commit is contained in:
Peter Klausler
2024-04-08 11:56:36 -07:00
committed by GitHub
parent aace1e1719
commit 97e3f605d5
3 changed files with 58 additions and 4 deletions
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4
flang/docs/Extensions.md
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@@ -346,6 +346,10 @@ end
* A `NAMELIST` input group may begin with either `&` or `$`.
* A comma in a fixed-width numeric input field terminates the
field rather than signaling an invalid character error.
* Arguments to the intrinsic functions `MAX` and `MIN` are converted
when necessary to the type of the result.
An `OPTIONAL`, `POINTER`, or `ALLOCATABLE` argument after
the first two cannot be converted, as it may not be present.
### Extensions supported when enabled by options

33
flang/lib/Semantics/check-call.cpp
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@@ -1466,6 +1466,29 @@ static void CheckImage_Index(evaluate::ActualArguments &arguments,
}
}
// Ensure that any optional argument that might be absent at run time
// does not require data conversion.
static void CheckMaxMin(const characteristics::Procedure &proc,
evaluate::ActualArguments &arguments,
parser::ContextualMessages &messages) {
if (proc.functionResult) {
if (const auto *typeAndShape{proc.functionResult->GetTypeAndShape()}) {
for (std::size_t j{2}; j < arguments.size(); ++j) {
if (arguments[j]) {
if (const auto *expr{arguments[j]->UnwrapExpr()};
expr && evaluate::MayBePassedAsAbsentOptional(*expr)) {
if (auto thisType{expr->GetType()};
thisType && *thisType != typeAndShape->type()) {
messages.Say(arguments[j]->sourceLocation(),
"An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE"_err_en_US);
}
}
}
}
}
}
}
// MOVE_ALLOC (F'2023 16.9.147)
static void CheckMove_Alloc(evaluate::ActualArguments &arguments,
parser::ContextualMessages &messages) {
@@ -1733,13 +1756,15 @@ static void CheckTransfer(evaluate::ActualArguments &arguments,
}
}
static void CheckSpecificIntrinsic(evaluate::ActualArguments &arguments,
SemanticsContext &context, const Scope *scope,
const evaluate::SpecificIntrinsic &intrinsic) {
static void CheckSpecificIntrinsic(const characteristics::Procedure &proc,
evaluate::ActualArguments &arguments, SemanticsContext &context,
const Scope *scope, const evaluate::SpecificIntrinsic &intrinsic) {
if (intrinsic.name == "associated") {
CheckAssociated(arguments, context, scope);
} else if (intrinsic.name == "image_index") {
CheckImage_Index(arguments, context.foldingContext().messages());
} else if (intrinsic.name == "max" || intrinsic.name == "min") {
CheckMaxMin(proc, arguments, context.foldingContext().messages());
} else if (intrinsic.name == "move_alloc") {
CheckMove_Alloc(arguments, context.foldingContext().messages());
} else if (intrinsic.name == "present") {
@@ -1790,7 +1815,7 @@ static parser::Messages CheckExplicitInterface(
CheckElementalConformance(messages, proc, actuals, foldingContext);
}
if (intrinsic) {
CheckSpecificIntrinsic(actuals, context, scope, *intrinsic);
CheckSpecificIntrinsic(proc, actuals, context, scope, *intrinsic);
}
return buffer;
}

25
flang/test/Semantics/intrinsics04.f90 Normal file
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@@ -0,0 +1,25 @@
! RUN: %python %S/test_errors.py %s %flang_fc1
! A potentially absent actual argument cannot require data type conversion.
subroutine s(o,a,p)
integer(2), intent(in), optional :: o
integer(2), intent(in), allocatable :: a
integer(2), intent(in), pointer :: p
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, max(1, 2, o)
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, max(1, 2, a)
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, max(1, 2, p)
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, min(1, 2, o)
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, min(1, 2, a)
!ERROR: An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE
print *, min(1, 2, p)
print *, max(1_2, 2_2, o) ! ok
print *, max(1_2, 2_2, a) ! ok
print *, max(1_2, 2_2, p) ! ok
print *, min(1_2, 2_2, o) ! ok
print *, min(1_2, 2_2, a) ! ok
print *, min(1_2, 2_2, p) ! ok
end