On Fri, Jul 15, 2011 at 14:43, Bernd <prof7...@googlemail.com> wrote:
> I am just trying to convert some openssl headers to Pascal (I know > that there is an openssl unit in the fpc packages but it is missing > the ECDSA functions which I will need later and which is main reason I > am starting to look into openssl). > > To get used to this entire thing I am beginning with something much > more simple, I will try to get some sha hashing functions from openssl > imported (I will also need them, so it would not hurt to start with > them). > > I am referring to the header file /usr/include/openssl/sha.h (pastebin > here: http://pastebin.com/dS8DY2z9 ) > > After appyling h2pas i have the following: http://pastebin.com/v3S3vtFR > > If I want to import functions in Pascal I would either declare them > external and explicitly tell it the name of the library binary (this > seems straightforward to me, I see no problems with this) or I load it > dynamically at runtime and then ask for the addresses of the functions > that I need and assign them to procedure variables (I have also done > this already on some occasions and it is equally easy to understand > and also raises no questions). > > I am confused about something else: > > When looking at the .h file and also when looking at the generated .pp > file it seems that nowhere in the header there was any information > about which .so (or .dll) to load or link against. It created empty > bodies with { you must implement this function }. Now the question > (and I am intentionally asking this on a Pascal list and not a C list > to get an answer that better fits into my Pascal brain) how would the > C compiler or linker know from where exactly to import these > functions? Where is this information, how are these C folks doing > these things, what kind of magic have they going on? > The information is located under /usrlib/pkgconfig/openssl.pc It tells to the configure script how to generate the Makefile and how to link stuff. It just a gcc syntax that is pasted back to the Makefile. I wrote a tool once (in Bash) that allow you properly search for a function inside an so to see who have it. If you wish, you can find it here: http://code.google.com/p/pasxlibbind/source/browse/trunk/find_function.sh > > confused, > Bernd > _______________________________________________ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > http://lists.freepascal.org/mailman/listinfo/fpc-pascal > Ido
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