[fpc-pascal] Is it possible to link to SO libraries that have filename ending like '.so.0'

[Michalis Kamburelis]

Peter Vreman wrote:
>>Hi
>>
>>This problem arised with recent change to JEDI-SDL, but it seems a
>>general problem with linking to libraries under UNIXes.
>>
>>Before the change, JEDI-SDL headers linked to libraries named like
>>'libSDL.so', using constructs that looked like (after removing preproc
>>$ifdefs and resolving constants)
>>
>>   procedure SDL_Quit; cdecl; external 'libSDL.so';
>>
>>and it worked OK. Of course, libSDL.so was on all systems only a symlink
>>to an actual so file, e.g. to 'libSDL-1.2.so.0.7.0' on my system.
>>
>>However, recently we're trying to link to 'libSDL-1.2.so.0', to make
>>sure that at compilation time we're linking to proper SDL version (since
>>JEDI-SDL headers were always supposed to work only with "rather new" SDL
>>version, not with "every possible SDL version". As is the case with most
>>header units.) But the problem is that doing
>>
>>   procedure SDL_Quit; cdecl; external 'libSDL-1.2.so.0';
>>
>>fails at linking with
>>
>>   /usr/bin/ld: cannot find -lSDL-1.2
>>   link_so_filename.dpr(4,1) Error: Error while linking
>>
>>So it seems that fpc passes to ld -lSDL-1.2, and ld looks for
>>'libSDL-1.2.so' (without '.0' suffix). Honestly, I don't know what one
>>should pass to ld to tell it to link to 'libSDL-1.2.so.0'.
>>
>>Question: Can this be somehow fixed in FPC ? Or is it just impossible
>>for FPC to say such thing to ld (so we have another problem that can't
>>be solved because FPC uses external linker) ?
>>
>>In another words, should this be considered something that must be fixed
>>in JEDI-SDL (by changing lib name back to 'libSDL.so') or can this be
>>fixed in newer FPC versions ? Or maybe it's all already working, but I
>>have to pass some command-line parameter to FPC or use some {$...}
>>preprocessor directive to make it work ?
> 
> 
> It is not possible for the compiler to detect if you want to link to a
> specific version or to the generic .so file. If you specify a complete
> filename then you must also pass the correct path where the file is
> located (In most cases /usr/lib) otherwise the linker can't find it. That
> means that the compiler needs to search for the file. This is not
> implemented.
> 
> 
> 
> 

You mean that
   procedure SDL_Quit; cdecl; external '/usr/lib/libSDL-1.2.so.0';
should work ? But it does not, fails with the same error as before. And 
I see that link.res sill contains lines

   INPUT(
   -lSDL-1.2
   )

Or do you mean by "This is not implemented" that for now compiler always 
strips path and extensions from specified library name, so even doing 
"external '/usr/lib/libSDL-1.2.so.0'" is not supposed to work now ?

-- 
Michalis