[Patch, Fortran][RFC] Re-add libgfortran's c_f_procpointer (PR 38871)

[Tobias Burnus <burnus at net-b dot de>]

Hi all,

when Chris added Bind(C) support he also included the libgfortran
function C_F_PROCPOINTER, which simply casted a pointer. As
procedure pointers were not supported back then, the function was
unused.

I removed the procedure from libgfortran after 4.3.0, when replacing
c_f_pointer (w/o SHAPE=) and c_f_procpointer with doing a proper
pointer assignment on tree level. As the first procedure pointer
patch was 2 months later, C_F_PROCPOINTER could not be used by
using "CALL C_F_PROCPOINTER" with procedure pointer arguments
(the "type(c_procptr)" data type existed but not the Fortran
proc pointer datatype).

Using the following program,

  use iso_c_binding
  type(c_ptr) :: fun
  integer, pointer :: bar
  call c_f_procpointer(fun,bar)
  end

one could call c_f_procpointer in 4.3 but the symbol generated was
      __iso_c_binding_c_f_procpointer_i4
which does never existed (only __iso_c_binding_c_f_procpointer existed).

Thus I still maintain what I wrote almost a year ago, when I submitted
the removal patch:

"As c_f_procpointer was never callable, I could remove it from the library."

Thus I believe one can close the bug as WONTFIX. Alternatively, one can
add the following patch, which re-adds the symbol.

Jakub, who has opened the P1 regression, writes there:
 "I'd say re-adding that symbol until you change libgfortran ABI wouldn't hurt
  anything, but if you can prove no program could ever use it except for
  referencing directly that symbol, I guess I can live with a WONTFIX too."

Tobias

2009-01-17  Tobias Burnus  <burnus@net-b.de>

       PR fortran/38871
       * intrinsics/iso_c_binding.c (c_f_procpointer): Re-add.
       * intrinsics/iso_c_binding.h (c_f_procpointer): Re-add.
       * gfortran.map (c_f_procpointer): Re-add.

Index: libgfortran/intrinsics/iso_c_binding.c
===================================================================
--- libgfortran/intrinsics/iso_c_binding.c	(Revision 143458)
+++ libgfortran/intrinsics/iso_c_binding.c	(Arbeitskopie)
@@ -180,3 +180,17 @@ ISO_C_BINDING_PREFIX (c_f_pointer_d0) (v
 			 | (GFC_DTYPE_DERIVED << GFC_DTYPE_TYPE_SHIFT);
     }
 }
+
+
+/* Unused function, initially planed for procedure pointers but never
+   used for it; cf. PR 38871.  TODO: Remove when bumping the library
+   version.  */
+
+void
+ISO_C_BINDING_PREFIX (c_f_procpointer) (void *c_ptr_in,
+                                        gfc_array_void *f_ptr_out)
+{
+  GFC_DESCRIPTOR_DATA(f_ptr_out) = c_ptr_in;
+}
+
+
Index: libgfortran/intrinsics/iso_c_binding.h
===================================================================
--- libgfortran/intrinsics/iso_c_binding.h	(Revision 143458)
+++ libgfortran/intrinsics/iso_c_binding.h	(Arbeitskopie)
@@ -41,6 +41,9 @@ typedef struct c_ptr
 }
 c_ptr_t;
 
+/* Unused structure, initially planed for procedure pointers but never
+   used for it.  TODO: Remove (when bumping the library
+   version?).  */
 typedef struct c_funptr
 {
   void *c_address;
@@ -57,4 +60,9 @@ void ISO_C_BINDING_PREFIX(c_f_pointer_u0
 void ISO_C_BINDING_PREFIX(c_f_pointer_d0) (void *, gfc_array_void *,
 					   const array_t *);
 
+/* Unused function, initially planed for procedure pointers but never
+   used for it; cf. PR 38871.  TODO: Remove when bumping the library
+   version.  */
+void ISO_C_BINDING_PREFIX(c_f_procpointer) (void *, gfc_array_void *);
+
 #endif
Index: libgfortran/gfortran.map
===================================================================
--- libgfortran/gfortran.map	(Revision 143458)
+++ libgfortran/gfortran.map	(Arbeitskopie)
@@ -1026,6 +1026,7 @@ GFORTRAN_1.0 {
     __iso_c_binding_c_f_pointer_l4;
     __iso_c_binding_c_f_pointer_l8;
     __iso_c_binding_c_f_pointer_u0;
+    __iso_c_binding_c_f_procpointer;
   local:
     *;
 };