FDATE extension implementation: get date and time in ctime format

reference to gfortran fdate https://gcc.gnu.org/onlinedocs/gfortran/FDATE.html
usage:
CHARACTER(32) :: time
CALL fdate(time)
WRITE(*,*) time

Author: yiwu0b11

flang/docs/Intrinsics.md

@@ -751,7 +751,7 @@ This phase currently supports all the intrinsic procedures listed above but the
 | Object characteristic inquiry functions | ALLOCATED, ASSOCIATED, EXTENDS_TYPE_OF, IS_CONTIGUOUS, PRESENT, RANK, SAME_TYPE, STORAGE_SIZE |
 | Type inquiry intrinsic functions | BIT_SIZE, DIGITS, EPSILON, HUGE, KIND, MAXEXPONENT, MINEXPONENT, NEW_LINE, PRECISION, RADIX, RANGE, TINY|
 | Non-standard intrinsic functions | AND, OR, XOR, SHIFT, ZEXT, IZEXT, COSD, SIND, TAND, ACOSD, ASIND, ATAND, ATAN2D, COMPL, EQV, NEQV, INT8, JINT, JNINT, KNINT, QCMPLX, DREAL, DFLOAT, QEXT, QFLOAT, QREAL, DNUM, NUM, JNUM, KNUM, QNUM, RNUM, RAN, RANF, ILEN, SIZEOF, MCLOCK, SECNDS, COTAN, IBCHNG, ISHA, ISHC, ISHL, IXOR, IARG, IARGC, NARGS, NUMARG, BADDRESS, IADDR, CACHESIZE, EOF, FP_CLASS, INT_PTR_KIND, ISNAN, MALLOC |
-| Intrinsic subroutines |MVBITS (elemental), CPU_TIME, DATE_AND_TIME, EVENT_QUERY, EXECUTE_COMMAND_LINE, GET_COMMAND, GET_COMMAND_ARGUMENT, GET_ENVIRONMENT_VARIABLE, MOVE_ALLOC, RANDOM_INIT, RANDOM_NUMBER, RANDOM_SEED, SYSTEM_CLOCK |
+| Intrinsic subroutines |MVBITS (elemental), CPU_TIME, DATE_AND_TIME, EVENT_QUERY, EXECUTE_COMMAND_LINE, FDATE, GET_COMMAND, GET_COMMAND_ARGUMENT, GET_ENVIRONMENT_VARIABLE, MOVE_ALLOC, RANDOM_INIT, RANDOM_NUMBER, RANDOM_SEED, SYSTEM_CLOCK |
 | Atomic intrinsic subroutines | ATOMIC_ADD |
 | Collective intrinsic subroutines | CO_REDUCE |
 

flang/include/flang/Runtime/command.h

@@ -23,6 +23,11 @@ extern "C" {
 // integer kind.
 std::int32_t RTNAME(ArgumentCount)();
 
+// Try to get the the current date (same format as CTIME: convert to a string)
+// Return a STATUS as described in the standard.
+std::int32_t RTNAME(FDate)(
+    const Descriptor *argument = nullptr, const Descriptor *errmsg = nullptr);
+
 // 16.9.82 GET_COMMAND
 // Try to get the value of the whole command. All of the parameters are
 // optional.

flang/include/flang/Runtime/extensions.h

@@ -24,6 +24,8 @@ void FORTRAN_PROCEDURE_NAME(flush)(const int &unit);
 // GNU Fortran 77 compatibility function IARGC.
 std::int32_t FORTRAN_PROCEDURE_NAME(iargc)();
 
+void FORTRAN_PROCEDURE_NAME(fdate)(std::int8_t *string, std::int64_t length);
+
 // GNU Fortran 77 compatibility subroutine GETARG(N, ARG).
 void FORTRAN_PROCEDURE_NAME(getarg)(
     std::int32_t &n, std::int8_t *arg, std::int64_t length);

flang/runtime/command.cpp

@@ -14,6 +14,7 @@
 #include "flang/Runtime/descriptor.h"
 #include <cstdlib>
 #include <limits>
+#include <time.h>
 
 namespace Fortran::runtime {
 std::int32_t RTNAME(ArgumentCount)() {
@@ -125,6 +126,33 @@ static bool FitsInDescriptor(
       kind, terminator, value);
 }
 
+void removeNewLine(char *str) {
+  char *newlinePos = strchr(str, '\n');
+  if (newlinePos != NULL) {
+    *newlinePos = '\0'; // Replace with null terminator
+  }
+}
+
+std::int32_t RTNAME(FDate)(const Descriptor *value, const Descriptor *errmsg) {
+  FillWithSpaces(*value);
+
+  time_t current_time;
+  time(&current_time);
+
+  char *time_string = ctime(&current_time);
+  removeNewLine(time_string);
+  std::int64_t stringLen{StringLength(time_string)};
+  if (stringLen <= 0) {
+    return ToErrmsg(errmsg, StatMissingArgument);
+  }
+
+  if (value) {
+    return CopyToDescriptor(*value, time_string, stringLen, errmsg);
+  }
+
+  return StatOk;
+}
+
 std::int32_t RTNAME(GetCommandArgument)(std::int32_t n, const Descriptor *value,
     const Descriptor *length, const Descriptor *errmsg, const char *sourceFile,
     int line) {

flang/runtime/extensions.cpp

@@ -30,6 +30,11 @@ void FORTRAN_PROCEDURE_NAME(flush)(const int &unit) {
 // RESULT = IARGC()
 std::int32_t FORTRAN_PROCEDURE_NAME(iargc)() { return RTNAME(ArgumentCount)(); }
 
+void FORTRAN_PROCEDURE_NAME(fdate)(std::int8_t *arg, std::int64_t length) {
+  Descriptor value{*Descriptor::Create(1, length, arg, 0)};
+  (void)RTNAME(FDate)(&value, nullptr);
+}
+
 // CALL GETARG(N, ARG)
 void FORTRAN_PROCEDURE_NAME(getarg)(
     std::int32_t &n, std::int8_t *arg, std::int64_t length) {

flang/unittests/Runtime/CommandTest.cpp

@@ -225,6 +225,12 @@ TEST_F(ZeroArguments, GetCommandArgument) {
   CheckMissingArgumentValue(1);
 }
 
+TEST_F(ZeroArguments, FDate) {
+  CheckMissingArgumentValue(-1);
+  CheckArgumentValue(commandOnlyArgv[0], 0);
+  CheckMissingArgumentValue(1);
+}
+
 TEST_F(ZeroArguments, GetCommand) { CheckCommandValue(commandOnlyArgv, 1); }
 
 static const char *oneArgArgv[]{"aProgram", "anArgumentOfLength20"};
@@ -242,6 +248,13 @@ TEST_F(OneArgument, GetCommandArgument) {
   CheckMissingArgumentValue(2);
 }
 
+TEST_F(OneArgument, FDate) {
+  CheckMissingArgumentValue(-1);
+  CheckArgumentValue(oneArgArgv[0], 0);
+  CheckArgumentValue(oneArgArgv[1], 1);
+  CheckMissingArgumentValue(2);
+}
+
 TEST_F(OneArgument, GetCommand) { CheckCommandValue(oneArgArgv, 2); }
 
 static const char *severalArgsArgv[]{
@@ -284,6 +297,7 @@ TEST_F(SeveralArguments, ArgValueTooShort) {
   ASSERT_NE(tooShort, nullptr);
   EXPECT_EQ(RTNAME(GetCommandArgument)(1, tooShort.get()), -1);
   CheckDescriptorEqStr(tooShort.get(), severalArgsArgv[1]);
+  EXPECT_EQ(RTNAME(FDate)(tooShort.get()), -1);
 
   OwningPtr<Descriptor> length{EmptyIntDescriptor()};
   ASSERT_NE(length, nullptr);