[libdvdcss-devel] Again: [PATCH] Re: libdvdcss.so does not distinguish internal from exposed API

[Fabian Greffrath]

Hello Reimar,

I have changed my mind. Sorry, but I think I was a bit hastly after 
reading the GNU document when I proposed the patch yesterday. All this 
second-guessing of specific architectures and compiler versions only 
makes things more error-prone and less intuitive.

All we need to know is if the currently used compiler supports ELF 
visibility - not its version nor architecture, not even if it compiles 
to ELF. We check this in the configure script and then somehow need to 
get this information into the header. I could not think up of a 
different solution than introducing a new #define, which is then 
checked for by the preprocessor. This means that this information is 
only available at build time of the library itself, but IMHO this is - 
in contrast to the __declspec() declarations used by WIN32 and CYGWIN 
compilers - perfectly suitable (because symbols are either hidden or 
exported at library build time).

Regarding the __declspec() declaration, both MinGW and CYGWIN (not to 
even speak of MSVC) compilers are GCC but do not produce ELF object 
code and thus - since visibility is an exclusive ELF feature - cannot 
support ELF visibility (confirmed myself with mingw at least). So they 
have to use the __declspec() declaration, depending on whether 
LIBDVDCSS_EXPORTS or LIBDVDCSS_IMPORTS is #defined. If none is them is 
defined, something is seriously borked anyway and the preprocessor 
falls back to "extern", but it was already like this before.

So please accept the attached patch as my hopefully final approach for 
this issue. :)

I have tested building libdvdcss on a current Debian unstable system 
with and without my patch and it works, i.e. with the patch 23 symbols 
from the _dvdcss_*, ioctl_* and _print_error name space are hidden.

Best regards,
Fabian
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