[fpc-pascal] readonly variables

[Jonas Maebe]

On 29 Nov 2009, at 22:59, Anthony Walter wrote:

>> Do you mean this one?
>> 
>> "Using const allows the compiler to optimize code for structured- and
>> string-type parameters."
>> 
>> "Allows" is not the same as "forces". This line in the help file does not
>> say that const parameters are passed by reference. It says that it may often
>> be so, perhaps all current implementations make it so, but it is by no means
>> guaranteed.
> 
> Martin Schreiber also chimed in, pointing out:
> 
> http://bit.ly/6uaAiB
> 
> "Larger sets, records, and static arrays are passed as 32-bit pointers
> to the value."

I believe that the previous thread that's referred to above was about cdecl functions: http://lists.freepascal.org/lists/fpc-pascal/2009-November/023125.html

And the documentation you linked goes on to say:

"[Larger sets, records, and static arrays are passed as 32-bit pointers to the value.] An exception to this rule is that records are always passed directly on the stack under the cdecl, stdcall, and safecall conventions; the size of a record passed this way is rounded upward to the nearest double-word boundary."

So it seems that passing them by value actually corresponds to what the Delphi docs say.


Jonas