[flang] Catch out-of-range constant arguments to CHAR/ACHAR

[klausler]

Summary

When folding the intrinsic functions CHAR and ACHAR, emit an
error message if the argument is out of the valid range for the
kind of the result.

[PeteSteinfeld]

All builds and tests correctly and looks good.

[PeteSteinfeld]

Actually, @klausler, I couldn't verify that this patch builds and tests correctly. I don't think that the file folding05.f90 was downloaded correctly to my machine. Note that Phabricator seems to think that it's a binary file.

[klausler]

In D142754#4086852, @PeteSteinfeld wrote:

Actually, @klausler, I couldn't verify that this patch builds and tests correctly. I don't think that the file folding05.f90 was downloaded correctly to my machine. Note that Phabricator seems to think that it's a binary file.

It does have some UTF-8 encodings in it.

[klausler]

Use "git show -a" to get a diff of a test file with some non-ASCII characters.

flang/lib/Evaluate/fold-character.cpp

Expr<Type<TypeCategory::Character, KIND>> FoldIntrinsicFunction(
   using StringType = Scalar<T>; // std::string or larger
   using SingleCharType = typename StringType::value_type; // char &c.
   auto *intrinsic{std::get_if<SpecificIntrinsic>(&funcRef.proc().u)};
   CHECK(intrinsic);
   std::string name{intrinsic->name};
   if (name == "achar" || name == "char") {
     using IntT = SubscriptInteger;
     return FoldElementalIntrinsic<T, IntT>(context, std::move(funcRef),
-        ScalarFunc<T, IntT>([](const Scalar<IntT> &i) {
+        ScalarFunc<T, IntT>([&](const Scalar<IntT> &i) {
+          if (i.IsNegative() || i.BGE(Scalar<IntT>{0}.IBSET(8 * KIND))) {
+            context.messages().Say(
+                "%s(I=%jd) is out of range for CHARACTER(KIND=%d)"_warn_en_US,
+                parser::ToUpperCaseLetters(name),
+                static_cast<std::intmax_t>(i.ToInt64()), KIND);
+          }
           return CharacterUtils<KIND>::CHAR(i.ToUInt64());
         }));
   } else if (name == "adjustl") {
     return FoldElementalIntrinsic<T, T>(
         context, std::move(funcRef), CharacterUtils<KIND>::ADJUSTL);
   } else if (name == "adjustr") {
     return FoldElementalIntrinsic<T, T>(
         context, std::move(funcRef), CharacterUtils<KIND>::ADJUSTR);

flang/test/Evaluate/errors01.f90

subroutine s9
     !CHECK: error: SOURCE= argument to SPREAD has rank 15 but must have rank less than 15
     integer, parameter :: bad1 = spread(rank15, 1, 1)
     integer, parameter :: matrix(2, 2) = reshape([1, 2, 3, 4], [2, 2])
     !CHECK: error: DIM=0 argument to SPREAD must be between 1 and 3
     integer, parameter :: bad2 = spread(matrix, 0, 1)
     !CHECK: error: DIM=4 argument to SPREAD must be between 1 and 3
     integer, parameter :: bad3 = spread(matrix, 4, 1)
   end subroutine
+  subroutine s10
+    !CHECK: warning: CHAR(I=-1) is out of range for CHARACTER(KIND=1)
+    character(kind=1), parameter :: badc11 = char(-1,kind=1)
+    !CHECK: warning: ACHAR(I=-1) is out of range for CHARACTER(KIND=1)
+    character(kind=1), parameter :: bada11 = achar(-1,kind=1)
+    !CHECK: warning: CHAR(I=-1) is out of range for CHARACTER(KIND=2)
+    character(kind=2), parameter :: badc21 = char(-1,kind=2)
+    !CHECK: warning: ACHAR(I=-1) is out of range for CHARACTER(KIND=2)
+    character(kind=2), parameter :: bada21 = achar(-1,kind=2)
+    !CHECK: warning: CHAR(I=-1) is out of range for CHARACTER(KIND=4)
+    character(kind=4), parameter :: badc41 = char(-1,kind=4)
+    !CHECK: warning: ACHAR(I=-1) is out of range for CHARACTER(KIND=4)
+    character(kind=4), parameter :: bada41 = achar(-1,kind=4)
+    !CHECK: warning: CHAR(I=256) is out of range for CHARACTER(KIND=1)
+    character(kind=1), parameter :: badc12 = char(256,kind=1)
+    !CHECK: warning: ACHAR(I=256) is out of range for CHARACTER(KIND=1)
+    character(kind=1), parameter :: bada12 = achar(256,kind=1)
+    !CHECK: warning: CHAR(I=65536) is out of range for CHARACTER(KIND=2)
+    character(kind=2), parameter :: badc22 = char(65536,kind=2)
+    !CHECK: warning: ACHAR(I=65536) is out of range for CHARACTER(KIND=2)
+    character(kind=2), parameter :: bada22 = achar(65536,kind=2)
+    !CHECK: warning: CHAR(I=4294967296) is out of range for CHARACTER(KIND=4)
+    character(kind=4), parameter :: badc42 = char(4294967296_8,kind=4)
+    !CHECK: warning: ACHAR(I=4294967296) is out of range for CHARACTER(KIND=4)
+    character(kind=4), parameter :: bada42 = achar(4294967296_8,kind=4)
+  end subroutine
   subroutine s12(x,y)
     class(t), intent(in) :: x
     class(*), intent(in) :: y
     !CHERK: error: Must be a constant value
     integer, parameter :: bad1 = storage_size(x)
     !CHERK: error: Must be a constant value
     integer, parameter :: bad2 = storage_size(y)
   end subroutine