Re: Interfacing between Ada and C: records and structs

[awdorrin <awdorrin@gmail.com>]

On Tuesday, July 31, 2012 1:16:10 PM UTC-4, Niklas Holsti wrote:
> 
> How is pthread_mutex_t declared in Ada form? And in C form?
> 

Digging into the POSIX module:

private
  type Dummy is tagged null record;
  type Mutex is record
    Mutex : aliased POSIX.C.pthread_mutex_t;
    D : Dummy;
  end record

> 
> Have you checked that in Ada, pthread_mutex_t'Size is 192?
> 

In the POSIX.C package:
ALIGNMENT : constant := Natural'Min(Standard'Maximum_Alignment, 8);
type pthread_mutex_t'Alignment use ALIGNMENT;
type pthread_mutex_t'Size use 192;

However, when I write a simple test program I get 256 bits from 'Size, I'm not sure why...
But that is probably the source of my problem.
 
> 
> What is the storage unit of your target processor? 8 bits?

The system is an Intel core2Duo E4600 - so a 64bit processor running x86_64 variant of Debian. (32-bit mode) So the storage unit is 8 bits.

> 
> That is a strange alignment. Do you see any need for it? If not, try
> removing it.

That was a typo on my part, should have read 'Alignment use 8;

> 
> Do you see any need for this representation clause? If not, remove it.
> 
> Or change it to use 192 bits per component.

That is the output from the -gnatR3 parameter, I don't have the rep spec defined in the code.

> 
> (What are the "-" characters after the "at" keywords? Shouldn't it read
> "at 0 range"?)

Sorry, that was apparently another typo on my part. (Cut and paste isn't working between my Linux VNC session and my desktop Windows PC)