[fpc-pascal] How to call lib routines with cdecl calling convention with win32 app?

[Jonas Maebe]

On 31 May 2009, at 15:28, Coco Pascal wrote:

> Marco van de Voort schreef:
>> In our previous episode, Coco Pascal said:
>>
>>> I have a library with udf routines using the cdecl calling  
>>> convention, required by Firebird. This seems to work well on win32.
>>
>> How exactly?
>>
>
> ?
>
> function Y_Odd(const AValue: Int64): LongInt; cdecl; export;
> begin
> if Odd(AValue) then
>   Result := -1
> else
>   Result := 0;
> end; {Y_Odd}
>
> exports
>
> Y_Odd;
>
> This works fine with Firebird. If I declare the stdcall calling  
> convention Firebird can't find its entrypoint.

cdecl automatically enables C-compiler-compatible name mangling for  
exported procedures. stdcall doesn't. So it's normal that Firebird  
does not find the entrypoint when using stdcall, as it does not  
support FPC-style name mangling.

There is no way to get C name mangling without the calling convention,  
so you have to manually declare an alias in that case. E.g.,

> function Y_Odd(const AValue: Int64): LongInt; cdecl; alias:  
> '_Y_Odd'; export;

Whether or not you need an extra underscore before the alias name  
depends on the target platform. Win32 requires one.


Jonas