[Flang] Support passing a function that returns procedure pointer as actual corresponding to a procedure dummy.

[DanielCChen]

Flang crashes with the following case. The problem is we missed the case when passing a reference to a function that returns a procedure pointer as actual that corresponds to a procedure dummy. This PR is to fix that.

  PROGRAM main
  IMPLICIT NONE
  INTERFACE
    FUNCTION IntF(Arg)
      integer :: Arg, IntF
    END FUNCTION
  END INTERFACE

  INTERFACE
    FUNCTION RetPtr(Arg)
      IMPORT
      PROCEDURE(IntF) :: Arg
      PROCEDURE(IntF), POINTER :: RetPtr
    END FUNCTION
  END INTERFACE

  CALL ModSub(RetPtr(IntF))
  contains
    SUBROUTINE ModSub(Fun1)
    PROCEDURE(IntF) :: Fun1
    END SUBROUTINE
  END

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

Author: Daniel Chen (DanielCChen)

Changes

Flang crashes a with the following case. The problem is we missed the case when passing a reference to a function that returns a procedure pointer as actual that corresponds to a procedure dummy. This PR is to fix that.

  PROGRAM main
  IMPLICIT NONE
  INTERFACE
    FUNCTION IntF(Arg)
      integer :: Arg, IntF
    END FUNCTION
  END INTERFACE

  INTERFACE
    FUNCTION RetPtr(Arg)
      IMPORT
      PROCEDURE(IntF) :: Arg
      PROCEDURE(IntF), POINTER :: RetPtr
    END FUNCTION
  END INTERFACE

  CALL ModSub(RetPtr(IntF))
  contains
    SUBROUTINE ModSub(Fun1)
    PROCEDURE(IntF) :: Fun1
    END SUBROUTINE
  END

---

Full diff: https://github.com/llvm/llvm-project/pull/80891.diff

1 Files Affected:

• (modified) flang/lib/Lower/ConvertCall.cpp (+4-2)

diff --git a/flang/lib/Lower/ConvertCall.cpp b/flang/lib/Lower/ConvertCall.cpp
index bb8fd2e945f43..bd6bd81117966 100644
--- a/flang/lib/Lower/ConvertCall.cpp
+++ b/flang/lib/Lower/ConvertCall.cpp
@@ -915,8 +915,10 @@ static PreparedDummyArgument preparePresentUserCallActualArgument(
   // Handle procedure arguments (procedure pointers should go through
   // prepareProcedurePointerActualArgument).
   if (hlfir::isFortranProcedureValue(dummyType)) {
-    // Procedure pointer actual to procedure dummy.
-    if (actual.isProcedurePointer()) {
+    // Procedure pointer or function returns procedure pointer actual to
+    // procedure dummy.
+    if (actual.isProcedurePointer() ||
+        actual.getType().isa<fir::BoxProcType>()) {
       actual = hlfir::derefPointersAndAllocatables(loc, builder, actual);
       return PreparedDummyArgument{actual, /*cleanups=*/{}};
     }

[jeanPerier]

Thanks for fixing this, nit but otherwise LGTM.

[DanielCChen]

@jeanPerier Please let me know if you have some other cases in mind. I can try those to confirm if the fix of this PR is good or not. Thanks!

[jeanPerier]

Thank, LGTM