This patch corrects the Ada-C parameter passing mechanism for record types. OUT
and IN OUT parameters are now unconditionally passed by reference regardless of
whether C_Pass_By_Copy is in effect. IN parameters subject to the convention
are passed by copy, otherwise they are passed by reference.
------------
-- Source --
------------
-- utils.ads
with Interfaces.C;
package Utils is
type Record_Type is record
A : Interfaces.C.int;
end record;
pragma Convention (C_Pass_By_Copy, Record_Type);
procedure Get_Data
(Result : out Interfaces.C.int;
In_Param : Record_Type;
Out_Param : out Record_Type);
pragma Export (C, Get_Data, "get_data");
pragma Export_Valued_Procedure (Get_Data);
end Utils;
-- utils.adb
with Ada.Text_IO; use Ada.Text_IO;
package body Utils is
procedure Get_Data
(Result : out Interfaces.C.int;
In_Param : Record_Type;
Out_Param : out Record_Type)
is
begin
Put_Line (" In data:");
Put_Line (" record field :" & In_Param.A'Img);
Result := 0;
Out_Param.A := 42;
Put_Line (" Returning data:");
Put_Line (" return code :" & Result'Img);
Put_Line (" record field :" & Out_Param.A'Img);
end Get_Data;
end Utils;
-- driver.c
#include <stdio.h>
#include <stdlib.h>
struct record_t {
int a;
};
extern int get_data(struct record_t in_param, struct record_t *out_param);
int main()
{
int ret;
struct record_t in_data, out_data;
printf("Initializing Ada Runtime\n");
adainit();
in_data.a = 4;
printf("Passing data\n");
printf(" record field : %d\n", in_data.a);
ret = get_data(in_data,&out_data);
printf("Returned data\n");
printf(" return code : %d\n", ret);
printf(" record field : %d\n", out_data.a);
printf("Expected value: 42\n");
printf("Finalizing Ada Runtime\n");
adafinal();
}
----------------------------
-- Compilation and output --
----------------------------
$ gcc -c driver.c
$ gnatmake -q -z utils -o driver -bargs -n -largs driver.o
$ ./driver
Initializing Ada Runtime
Passing data
record field : 4
In data:
record field : 4
Returning data:
return code : 0
record field : 42
Returned data
return code : 0
record field : 42
Expected value: 42
Finalizing Ada Runtime
Tested on x86_64-pc-linux-gnu, committed on trunk
2012-08-06 Hristian Kirtchev <kirtc...@adacore.com>
* sem_mech.adb (Set_Mechanisms): OUT and IN OUT parameters are
now unconditionally passed by reference. IN parameters subject
to convention C_Pass_By_Copy are passed by copy, otherwise they
are passed by reference.
Index: sem_mech.adb
===================================================================
--- sem_mech.adb (revision 190155)
+++ sem_mech.adb (working copy)
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
--- Copyright (C) 1996-2011, Free Software Foundation, Inc. --
+-- Copyright (C) 1996-2012, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
@@ -352,13 +352,13 @@
-- Access parameters (RM B.3(68))
-- Access to subprogram types (RM B.3(71))
- -- Note: in the case of access parameters, it is the
- -- pointer that is passed by value. In GNAT access
- -- parameters are treated as IN parameters of an
- -- anonymous access type, so this falls out free.
+ -- Note: in the case of access parameters, it is the pointer
+ -- that is passed by value. In GNAT access parameters are
+ -- treated as IN parameters of an anonymous access type, so
+ -- this falls out free.
- -- The bottom line is that all IN elementary types
- -- are passed by copy in GNAT.
+ -- The bottom line is that all IN elementary types are
+ -- passed by copy in GNAT.
if Is_Elementary_Type (Typ) then
if Ekind (Formal) = E_In_Parameter then
@@ -385,10 +385,21 @@
if Convention (Typ) /= Convention_C then
Set_Mechanism (Formal, By_Reference);
- -- If convention C_Pass_By_Copy was specified for
- -- the record type, then we pass by copy.
+ -- OUT and IN OUT parameters of record types are passed
+ -- by reference regardless of pragmas (RM B.3 (69/2)).
- elsif C_Pass_By_Copy (Typ) then
+ elsif Ekind_In (Formal, E_Out_Parameter,
+ E_In_Out_Parameter)
+ then
+ Set_Mechanism (Formal, By_Reference);
+
+ -- IN parameters of record types are passed by copy only
+ -- when the related type has convention C_Pass_By_Copy
+ -- (RM B.3 (68.1/2)).
+
+ elsif Ekind (Formal) = E_In_Parameter
+ and then C_Pass_By_Copy (Typ)
+ then
Set_Mechanism (Formal, By_Copy);
-- Otherwise, for a C convention record, we set the
