On 07 Sep 2007, at 12:54, Adriaan van Os wrote:
I am trying to find out whether or not to use an underscore prefix
when declaring external C functions in FPC using 'external name
xxx'. It looks like on Windows the underscore is not needed,
whereas on Mac OS X the underscore is required, even when on both
platforms 'nm' reveals that the to-be-linked-in C library has an
underscore before the C function names.
Note that the Mac OS X Pascal (Carbon) Interfaces for fpc use the
underscore, whereas the same Pascal Interfaces for gpc don't.
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.
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).
Jonas
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