Ada calling Pascal (working) : (was Ada calling Pascal (not working))

[lanceboyle at qwest.net]

Thanks for the helpful hints from both the Ada (GNAT) and Pascal  
(GPC) lists. This Ada and gcc newbie and C don'twannabe appreciates it!

I now have examples of Ada main program calling Pascal and Pascal  
main program calling Ada. I hope this helps someone.

Here is the cleanest and best-looking example, putting together hints  
from both lists. To Waldek Hebisch, your method of "pchar" and  
"ppchar" also works and is really the same, but using System.Address  
looks a little more Ada-like. Thanks Jim Hopper for your input--I  
need to study up on "aliased".

Sorry for the cross-post.

Jerry


<Ada main program>
with Ada.Text_IO;         use Ada.Text_IO;
with Ada.Command_Line;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with System;

procedure Ada_Calls_Pascal is

	Gnat_argc : aliased Integer;
	pragma Import (C, Gnat_argc);
	
	Gnat_argv : System.Address; -- Just get the base address to argv,  
like C
	pragma Import (C, Gnat_argv);

     Gnat_envp : System.Address; -- Same for envp.
     pragma Import (C, Gnat_envp);

     procedure MyPascalProcedure (anInteger : Integer);
     pragma Import(Convention => C, Entity => MyPascalProcedure);

     procedure p_initialize(
         Number_of_Arguments                   : Integer;
         Command_Vector, Environment_Variables : System.Address;
         Options                               : Integer);
     pragma Import(Convention => C, Entity => p_initialize,  
External_Name => "_p_initialize");

     procedure init_pascal_main_program;
     pragma Import(Convention => C, Entity => init_pascal_main_program,
		External_Name => "_p__M0_init");

     procedure p_finalize;
     pragma Import(Convention => C, Entity => p_finalize,  
External_Name => "_p_finalize");

     Argument_Count_Plus_1 : Integer;
     Command_Name_String   : String := Ada.Command_Line.Command_Name;  
-- C's argv[0]

begin
     Put_Line ("Hello from Ada_Calls_Pascal.");

	-- Here is the "Ada way" of handling command line arguments.
	Argument_Count_Plus_1 := Ada.Command_Line.Argument_Count + 1; -- the  
usual C-style argc
	Put("Number of arguments counting the command name is ");
     Put(Argument_Count_Plus_1); New_Line;

     Put_Line("Program is called " & Command_Name_String);
     Put_Line("Its arguments, if any, are:");
     for Argument_Index in 1..Ada.Command_Line.Argument_Count loop
         Put_Line(Ada.Command_Line.Argument(Argument_Index)); -- C's  
argv[1...]
     end loop;

	-- Show that we also can do things the "C way."
     Put("argc = ");
	Put(Gnat_argc); New_Line;

     -- Initialize the Pascal runtime system before calling any  
Pascal routines.
     p_initialize (Gnat_argc, Gnat_argv, Gnat_envp, 0);

	-- Initialize the user's Pascal main program.
     init_pascal_main_program;

	-- Run a user Pascal procedure.
     MyPascalProcedure(42);

	-- Finalize the Pascal world before leaving.
     p_finalize;

     Put_Line ("Goodbye from Ada_Calls_Pascal.");
end Ada_Calls_Pascal;



<Pascal called program>
program MyPascalProgram(input, output);

{$gpc-main=dummy}

     procedure MyPascalProcedure(anInteger : integer); attribute 
( name = 'mypascalprocedure');
     begin
         writeln('The integer from the Pascal procedure is: ',  
anInteger:1);
     end;

begin
{When exported to Ada, this part should not be called.}
writeln('In MyPascalProgram; error if calling from Ada.');
end.


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