[fpc-pascal] Underscore prefix for external C functions

Adriaan van Os fpc at microbizz.nl
Fri Sep 7 14:31:40 CEST 2007

Jonas Maebe wrote:

>> Is this just a mess or do I miss the true logic behind it ?
> If you declare an external function/procedure as "cdecl", the compiler 
> with /always/ add the necessary C-prefix (if any) to the external name.

I see, so if I add

{$ifdef FPC}
{$calling cdecl}

and skip the underscore, this results in multi-platform and gpc compatible 'external name xxx" 

> The universal interfaces are declared as mwpascal rather than cdecl, and 
> such functions/procedures do not automatically get the C-prefix 
> (although one might argue that it would have been better if they did, 
> and indeed if FPC on all platforms by default prefixed all its symbol 
> names with the same prefix as the main C compiler(s), but the fact is 
> that it doesn't do so today -- but maybe this could be changed now that 
> there still aren't many FPC shared libraries in common use).


> To make matters even more interesting (in the Chinese sense), there are 
> also {$mode macpas} interface-only units (i.e., units without an 
> implementation section, like many of the universal interfaces). Because 
> this support was added solely for the purpose of supporting (older 
> versions of) the universal interfaces, in that case any function without 
> an explicitly specified external name also gets the C-prefix added 
> (which does not apply to the universal interfaces units, since all 
> functions/procedures there do have an explicitly specified external name).

Are you saying that adding IMPLEMENTATION BEGIN changes the meaning of the INTERFACE section. That 
is hardly a defendable compiler feature, is it ?


Adriaan van Os

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