Re: Ada array vs C pointer (call by reference)

["Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org>]

Adrian Hoe wrote:
> 
> Can I use Float instead of Interfaces.C.C_Float?

You can use anything you want: Boolean, Duration, a task type, ...

But if you want to be sure it will work, you'll use Interfaces.C.C_Float.

> Why use Interfaces.C.Int, Interfaces.C.C_Float since they are all new
> declaration of Ada types.
> 
> I know it is for readability and maintainability but the question is
> logical as the declaration in Interfaces.C is just merely creating a
> new Ada type with a new name, unless there is pragma Convention
> statement after every such declaration in Interfaces.C.

I suggest you read ARM B.3. There you'll find, "Each of the types declared in 
Interfaces.C is C-compatible."

> Wouldn't it be better to write as such?
> 
> type C_Data is array (Positive range <>) of Float;
> pragma Convention (C, C_Data);

Not if you want to be sure it will work.

> Is PWM_Data passed as pointer to pwmRead?

B.3 also contains, "An Ada parameter of an array type with component type T, of 
any mode, is passed as a t* argument to a C function, where t is the C type 
corresponding to the Ada type T."

-- 
Jeff Carter
"Hello! Smelly English K...niggets."
Monty Python & the Holy Grail
08