Free-ing memory: not springing leaks?

[chris <spamoff.danx@ntlworld.com>]

Hi,

When you bind to c code, how do you deal with memory?  I bound to a 
function in Lua,

    function Lua_Version return ICS.Chars_Ptr;
    pragma Import (C, Lua_Version);

but upon free-ing the memory it gave a storage_error.

    function Version return String is
       X : ICS.Chars_Ptr := Lua_Version;
    begin
       declare
          Y : String := ICS.Value (X);
       begin
          ICS.Free (X);
          return Y;
       end;
    end Version;

To be clear, my understanding of this code is it get's a ptr to a null 
terminated string from Lua_Version, get's that value as a string, frees 
the null terminated string and returns the ada string.  Clearly, 
something is wrong with my understanding of how this works; if you free 
the memory it gives a storage error.

How then, do you deal with memory leaks?  If you bind to a c function 
and it allocates a chunk of memory and returns it, how do get rid of it 
and not cause leaks?  Remove Free and no error occurs.  Perhaps this is 
a special case?

I vaguely recall reading somewhere that in general you shouldn't free C 
allocated memory from Ada, but perhaps I was mistaken?


Can anyone please help with some advice or clarification?  I have only 
ever preallocated memory, passed it to a C function and released it 
afterwards (e.g. to pass strings into C functions) not had memory given 
by a c function and tried to release it.


Thanks,
Chris