Re: converting pointer to value

["Björn Lundin" <b.f.lundin@gmail.com>]

Den 2021-03-04 kl. 18:35, skrev Dmitry A. Kazakov:
> On 2021-03-04 17:55, Shark8 wrote:
> 
>>> type SQLPOINTER is private;
>> ....
>>> private
>>> type SQLPOINTER is new System.Storage_Elements.Integer_Address;
>>
>> And here we have SQLPOINTER, which is private, but which is something 
>> of the same representation that Integer_Address has; let's assume that 
>> the ADDRESS type is implementation-defined, and a private type.
> 
> SQLPOINTER is System.Address.
> 
>> What does this mean?
>> It means that we don't know what the size of ADDRESS (and thus 
>> SQLPOINTER) actually is, but assuming you're on a 32- or 64-bit 
>> machine it's likely 2 to 4 times as large as the 16-bit SQLSMALLINT-- 
>> which is a good indication that a simple UNCHECKED_CONVERSION is the 
>> wrong answer.
> 
> You need not to know that:
> 
>     declare
>        P : SQLPOINTER := ...;
>        A : System.Address;
>        pragma Import (Ada, A);
>        for A'Address use P'Address;
>        T : My_Fancy_Object;
>        pragma Import (Ada, My_Fancy_Object);
>        for T'Address use A;
>     begin
>        ... -- Use T at P
> 


so I tried this version:

procedure Exec (Statement_Handle : in Sqlhstmt) is
     Rc      :  Sqlreturn := Sqlexecute (Statement_Handle);
     Pvalue  : aliased Sqlpointer;
     Sent    : Integer := 0;
     Datalen : Integer := 14;
     Buffer  : String  (1..10) := (others => ' ');
     S_Ptr   : Ptr_String;

     A       :  System.Address;
     pragma Import(Ada,A);
     for A'Address use Pvalue'Address;
     I       : Sqlinteger ;
     pragma Import(Ada,I);
     for I'Address use A;

   begin
     --test for unset clob
     Rc := Sqlparamdata (Statement_Handle,Pvalue'Access);
     Text_Io.Put_Line ("SQLParamData1.2: " & I'Img );


SQLParamData1.2:  4790608


I'm thinking that I may be dealing with a pointer to a pointer here?
hmm, needs more testing. I changed the expected value from 5 to 7. Still 
a bit off...



-- 
Björn