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From: Paul Chardon <paul.chardon@avions.aerospatiale.fr>
Subject: String Allocation when Interfacing C with Ada
Date: 1996/12/05
Message-ID: <32A6D464.41C67EA6@avions.aerospatiale.fr>#1/1
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Date: 1996-12-05T00:00:00+00:00
List-Id: <comp.lang.ada>


Hello,
	I'm writing a C program using a string, this string is passed as
parameter to an Ada subprogram in order to modify its value. Is there
any problem of allocation or deallocation in this case.

For instance:

-- The main C program
void Handle_String(char * s);
main ()
{
   char *a_string

   strcpy(a_string,"high");
   printf("String Value : %s \n", A_String);
   adainit();
   Handle_String(A_String);
   printf("String Value : %s \n",A_String);
   /* Print only value token in account when using strcpy in the Ada
      subprogram, not when using "Ada allocation" */
   adafinal();
}
-- The imported Ada subprogram
with Interfaces.C.Strings;
with Text_Io;
procedure Handle_String(S : in out Interfaces.C.Strings.Chars_ptr) is

	procedure C_Strcpy
	(Target :    out Interfaces.C.Strings.Chars_Ptr;
         Source : in     Interfaces.C.Strings.Chars_Ptr);
	pragma import(C, C_Strcpy,"strcpy");

begin
	-- THAT CALL 
	S := Interfaces.C.Strings.New_String
	     ("Value not token in account");
	-- when I put only this call, no value is printed in the C 			--
program
	-- OR THIS OTHER CALL
	C_Strcpy(S,
		 Interfaces.C.Strings.New_String
		 ("Value token in account"));
	-- When I do that copy instead of the first allocation call, the 		--
good value is printed in C main function
end Handle_String;
pragma Export(C, Handle_String, "Handle_String");

	If anyone can explain why it doesnt works in the first call case.
Thanks in advance, Paul.