- Interface declaration has External
Every implementation declaration will give an error: (03210_E_Procedure is already declared EXTERNAL)

- Interface declaration has no External
Implementation has External
- For Win32 (maybe OS/2 also?) this is allowed when the import is done from a DLL, e.g. "external dllname name 'fsdfds'" or "cdecl;external dllname"
- Otherwise it gives an error (because the assembler name becomes different from the one already set in the interface) (03211_E_Can't declare procedure as EXTERNAL)

This is not Delphi compatible ...

This is not Delphi compatible ...

Ofcourse we check this before changing things like this. Delphi only accepts the next directive for importing from DLLs:

external 'dllname' name 'functionname'

FPC supports besides importing from DLLs also referencing other public accessible assembler symbols. These can come from sharedlibraries or from linked objects or even from routines in pascal that are declared public.

external name 'functionname'
external 'dllname'

If no functionname is specified the following rules are used:
- default is to use the name as written in the source
- for cdecl declared procedures the name as written in the source prepended with _ (for most targets, some don't need the _ prefix)

For referencing functions with external in your own program or exporting for referencing from other languages like C:

public
public name 'functionname'

For the functionname the same rules as with external apply (as written in source and for cdecl prepended with a _)

But e.g.
gcc -c -o test.ow test.c
produces identifiers *without* "_"-prefix

But e.g. gcc -c -o test.ow test.c produces identifiers *without* "_"-prefix

That is why you also can use "external name 'namewithoutunderscore'"

That's not entirely correct. If gcc adds an underscore to the start of symbol names by default on the target we're compiling for, then FPC will also add an underscore if you use something like this:

procedure test; cdec; external name 'test';

The reason is that otherwise such declarations become unportable and require ifdef's depending on whether or not the target platform uses an underscore by default. If you don't make the routine "cdecl", then the underscore will never be added of course (but then the routine also won't follow C calling conventions).

Jonas