Re: Ada and string literals

[gautier_niouzes@hotmail.com]

Le mercredi 30 janvier 2013 17:52:32 UTC+1, codeallergy a écrit :

> another question: how free a object from a procedure ?

with Ada.Unchecked_Deallocation;
...
  procedure Free is new Ada.Unchecked_Deallocation(String, String_Access);

> example:
> procedure Free_Abc (Target : access String)
> is
> begin
>    GNAT.Strings.Free(Target); -- error
> end Free_Abc;
> 
> this code produce the error: actual for "X" must be a variable
> 
> why disallow that ?

The access parameter seems to be like an "in" parameter and treated as a local constant (only a guess, I don't use access parameters).
What you pass as an "in" parameter is not certainly a variable
You could have a call like Free_Abc(null);
Similarly you could have

procedure Do_something(x: in Integer) is
begin
  x:= x + 1; -- same error
end;

But with the "in" parameter, you could have a call like
Do_something(1234);
which makes the x:= x + 1 nonsensical.

Cheers
Gautier