[flang] Allow NULL() actual argument for optional dummy procedure

A disassociated procedure pointer is allowed to be passed as an absent
actual argument that corresponds to an optional dummy procedure,
but not NULL(); accept that case as well.

Differential Revision: https://reviews.llvm.org/D125127

2 files changed, 11 insertions, 1 deletions

diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
index 8f49953f4b14..fee716248cbf 100644
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -635,7 +635,9 @@ static void CheckProcedureArg(evaluate::ActualArgument &arg,
               dummyName);
         }
       } else if (IsNullPointer(*expr)) {
-        if (!dummyIsPointer) {
+        if (!dummyIsPointer &&
+            !dummy.attrs.test(
+                characteristics::DummyProcedure::Attr::Optional)) {
           messages.Say(
               "Actual argument associated with procedure %s is a null pointer"_err_en_US,
               dummyName);
diff --git a/flang/test/Semantics/call02.f90 b/flang/test/Semantics/call02.f90
index dfd1ba5537d4..a4ceaf65d1ed 100644
--- a/flang/test/Semantics/call02.f90
+++ b/flang/test/Semantics/call02.f90
@@ -15,6 +15,12 @@ subroutine s01(elem, subr)
       !ERROR: A dummy procedure may not be ELEMENTAL
       procedure(elem) :: dummy
     end subroutine
+    subroutine optionalsubr(dummy)
+      procedure(sin), optional :: dummy
+    end subroutine
+    subroutine ptrsubr(dummy)
+      procedure(sin), pointer, intent(in) :: dummy
+    end subroutine
   end interface
   intrinsic :: cos
   call subr(cos) ! not an error
@@ -22,6 +28,8 @@ subroutine s01(elem, subr)
   call subr(elem) ! C1533
   !ERROR: Actual argument associated with procedure dummy argument 'dummy=' is a null pointer
   call subr(null())
+  call optionalsubr(null()) ! ok
+  call ptrsubr(null()) ! ok
   !ERROR: Actual argument associated with procedure dummy argument 'dummy=' is typeless
   call subr(B"1010")
 end subroutine