[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

   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") {

flang/test/Evaluate/errors01.f90

     !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 warnings
     real, parameter :: ok1 = scale(0.0, 99999) ! 0.0
     real, parameter :: ok2 = scale(1.0, -99999) ! 0.0

flang/test/Evaluate/folding05.f90

   logical, parameter :: test_char1_ok2 = char(127_4, 1).EQ."␡"
   logical, parameter :: test_char1_ok3 = char(97_4, 1).EQ."a"
   logical, parameter :: test_char1_ok4 = .NOT.char(97_4, 1).EQ."b"
+  !WARN: warning: CHAR(I=355) is out of range for CHARACTER(KIND=1)
   logical, parameter :: test_char1_ok5 = char(355_4, 1).EQ."c"
+  !WARN: warning: CHAR(I=-61) is out of range for CHARACTER(KIND=1)
   logical, parameter :: test_char1_ok6 = char(-61_1, 1).EQ.char(195_4, 1)
 
   logical, parameter :: test_char2_ok1 = char(0_4, 2).EQ.2_"␀"

   logical, parameter :: test_char4_ok1 = char(0, 4).EQ.4_"␀"
   logical, parameter :: test_char4_ok2 = char(INT(12435, 4), 4).EQ.4_"ん"
   logical, parameter :: test_char4_ok3 = char(354_4, 4).EQ.4_"Ţ"
+  !WARN: warning: CHAR(I=-1) is out of range for CHARACTER(KIND=4)
   logical, parameter :: test_char4_ok4 = char(-1_1, 4).EQ.char(x'ffffffff', 4)
 
   character(kind=4, len=*), parameter :: c4aok(*) = char([97_4, 98_4, 99_4, 20320_4, 22909_4], 4)

   logical, parameter :: test_ichar1 = char(ichar("a")).EQ."a"
   logical, parameter :: test_ichar2 = ichar(char(255)).EQ.255
   !WARN: warning: Result of intrinsic function 'ichar' (255) overflows its result type
+  !WARN: warning: CHAR(I=-1) is out of range for CHARACTER(KIND=1)
   logical, parameter :: test_ichar3 = ichar(char(-1_1), 1).EQ.-1_1
   logical, parameter :: test_ichar4 = ichar(char(2147483647_4, 4), 4).EQ.2147483647_4
   logical, parameter :: test_ichar5 = ichar(char(4294967295_8, 4), 8).EQ.4294967295_8
+  !WARN: warning: CHAR(I=4294967296) is out of range for CHARACTER(KIND=4)
   logical, parameter :: test_ichar6 = ichar(char(4294967296_8, 4), 8).EQ.0_8
   logical, parameter :: test_iachar1 = achar(iachar("a")).EQ."a"
   logical, parameter :: test_iachar2 = iachar(achar(22)).EQ.22
   !WARN: warning: Result of intrinsic function 'ichar' (2147483649) overflows its result type
+  !WARN: warning: CHAR(I=-2147483647) is out of range for CHARACTER(KIND=4)
   logical, parameter :: test_iachar3 = ichar(char(-2147483647_4, 4), 4).EQ.(-2147483647_4)
   logical, parameter :: test_iachar5 = ichar(char(65535_4, 2), 4).EQ.65535_4
+  !WARN: warning: CHAR(I=65536) is out of range for CHARACTER(KIND=2)
   logical, parameter :: test_iachar6 = ichar(char(65536_4, 2), 4).EQ.0_4
 
   ! Not yet recognized as intrinsic