[fpc-pascal] Mozilla XPCOM

[Jonas Maebe]

On 07 Jun 2010, at 17:11, José Mejuto wrote:

> Wow, that looks "dangerous" at least it should produce a warning when
> used in interfaces, or as safecall is a form of stdcall (with return
> values check) replace by stdcall.

Yes, probably. The reason was that nobody knew that this calling convention made any sense at all on non-Windows platforms, so its appearance was assumed to be a porting artefact.

> JM> At first sight that does not happen in XPCOM, even on Windows (but
> JM> since we do it on Windows, maybe we should also do it elsewhere for
> JM> consistency reasons).
> 
> Maybe, but that's not a great problem, maybe do it only in the case of
> "Verify method calls" ?

Only if it's only done on Windows in that case as well.

> JM> b) a lot of people use Pascal "const" as translation for C's "const *"
> JM> for record parameters, which is wrong (but which sometimes works by
> JM> accident)
> 
> Yes, but removing the "const" still passes the parameter as 16 bytes,
> and defining it as "var" creates problems when passing an interface to
> extract the GUID instead passing the interface reference. Anyway most
> of this problems are quite easy to be bypassed with some source
> changes which still remain compatible between windows and linux.

In such cases, the parameter should be a pointer. It's probably "const" for Delphi compatibility (which probably guarantees passing const records by reference for safecall, and hence FPC probably also does on platforms that support it).

> JM> I'm personally not really interested in fixing this whole mess though.
> JM> I spend a lot of time in the past disabling safecall in the compiler
> JM> for all non-Windows platforms because it always generated wrong code
> JM> elsewhere. Now it seems it should be
> JM> a) enabled everywhere, and then
> JM> b) fixed for all platforms, which requires modification to the  
> JM> parameter managers of most architectures (since most don't contain any
> JM> support for safecall)
> 
> That looks as a hard job :( I can only help testing XPCOM in both
> windows and linux, but I doubt that I can help in the compiler side :(

You should file a bug report.


Jonas