Compiler-specific compilation failures in NST component related to dummy procedures of AGRIF subroutines

[smueller]

Context

Not all commonly used compilers succeed in compiling the calls of AGRIF subroutines Agrif_Bc_variable and Agrif_Update_variable in component NST.

Analysis

The AGRIF subroutines Agrif_Bc_variable and Agrif_Update_variable use a dummy procedure argument with an implicit interface (argument name procname). Currently, the respective calls in the NST component (e.g., source:/NEMO/releases/r4.0/r4.0.6/src/NST/agrif_ice_update.F90#L67​) refer to a procedure name as argument value, which not all commonly used compilers seem to accept.

Recommendation

The procname argument values in the Agrif_Bc_variable and Agrif_Update_variable calls included in the NST component could be replaced by explicitly assigned procedure pointers with implicit interface, such as

src/NST/agrif_ice_update.F90

@@ -48 +48 @@
       !! 
       !! ** Action : - Update (u_ice,v_ice) and ice tracers
       !!----------------------------------------------------------------------
+!$AGRIF_DO_NOT_TREAT
+      PROCEDURE(), POINTER ::   zp_update_tra_ice, zp_update_u_ice, zp_update_v_ice
+!$AGRIF_END_DO_NOT_TREAT
+      !!----------------------------------------------------------------------
       !
       IF( Agrif_Root() .OR. nn_ice == 0 ) RETURN   ! do not update if inside Parent Grid or if child domain does not have ice
       !
@@ -62 +66 @@
       Agrif_SpecialValueFineGrid    = -9999.
       Agrif_UseSpecialValueInUpdate = .TRUE.
       
+      zp_update_tra_ice => update_tra_ice
+      zp_update_u_ice   => update_u_ice
+      zp_update_v_ice   => update_v_ice
 # if defined TWO_WAY
 # if ! defined DECAL_FEEDBACK
-      CALL Agrif_Update_Variable( tra_ice_id , procname = update_tra_ice  )
+      CALL Agrif_Update_Variable( tra_ice_id , procname=zp_update_tra_ice )
 #else 
-      CALL Agrif_Update_Variable( tra_ice_id , locupdate=(/1,0/), procname = update_tra_ice  )
+      CALL Agrif_Update_Variable( tra_ice_id , locupdate=(/1,0/), procname=zp_update_tra_ice )
 #endif 
 # if ! defined DECAL_FEEDBACK
-      CALL Agrif_Update_Variable( u_ice_id   , procname = update_u_ice    )
-      CALL Agrif_Update_Variable( v_ice_id   , procname = update_v_ice    )
+      CALL Agrif_Update_Variable( u_ice_id   , procname=zp_update_u_ice )
+      CALL Agrif_Update_Variable( v_ice_id   , procname=zp_update_v_ice )
 #else 
-      CALL Agrif_Update_Variable( u_ice_id   , locupdate1=(/0,-1/),locupdate2=(/1,-2/),procname=update_u_ice)
-      CALL Agrif_Update_Variable( v_ice_id   , locupdate1=(/1,-2/),locupdate2=(/0,-1/),procname=update_v_ice)
+      CALL Agrif_Update_Variable( u_ice_id   , locupdate1=(/0,-1/), locupdate2=(/1,-2/), procname=zp_update_u_ice )
+      CALL Agrif_Update_Variable( v_ice_id   , locupdate1=(/1,-2/), locupdate2=(/0,-1/), procname=zp_update_v_ice )
 #endif
 !      CALL Agrif_Update_Variable( tra_ice_id , locupdate=(/0,2/), procname = update_tra_ice  )
 !      CALL Agrif_Update_Variable( u_ice_id   , locupdate=(/0,1/), procname = update_u_ice    )

to improve the compiler compatibility of the NST component.