That's the remains of a failed experiment several years ago to see if I 
could build a Windows DLL using GCC/Cygwin. I ended up getting a lot of 
linker errors and didn't pursue it further, but left the entries in the 
GNUmakefile in case I or someone else wanted to try again later.

The problem with this approach is that the symbols marked CRYPTOPP_DLL are 
only a part of Crypto++ that is FIPS-approved. If you want to use 
non-FIPS-approved algorithms, such as curve25519, you'll also need to link 
with a static library that includes the non-FIPS-approved parts of Crypto++. 
It's probably easier to link with just the full static library than to get 
this unconventional library structure accepted into Linux distributions.

If linking with the static library form of Crypto++ doesn't work, I think 
your workaround option 2 (in your post to cplusplus-sig) is best. Perhaps if 
you file a bug on RTLD_GLOBAL, it will be fixed by the time someone wants to 
import two different python modules that link to libcryptopp.so. 
http://gcc.gnu.org/faq.html#dso also says to use RTLD_GLOBAL, BTW. It also 
says you have to use "-Wl,-E". Are you doing that already?

--------------------------------------------------
From: "Zooko Wilcox-O'Hearn" <[email protected]>
Sent: Tuesday, May 26, 2009 8:03 AM
To: "Wei Dai" <[email protected]>
Cc: "Crypto++ Users" <[email protected]>
Subject: Re: that problem with comparing types across DLLs

>
> Dear Wei Dai, et al.:
>
> By the way, who added the features to GNUmakefile to build a "dll"
> using gcc?  And what is it for?
>
> I'm guessing that this is for building a DLL on Windows where "gcc"
> means mingw.  I've been tinkering with porting it to Linux in order
> to build a dynamic library (.so) on Linux which exports only the
> symbols marked by "CRYPTOPP_DLL".  There appears to be some bitrot,
> for example the DLLSRCS variable in GNUmakefile seems to omit
> some .cpp files that are necessary, possibly because those .cpp files
> were added after this feature of the GNUmakefile was added.
>
> Regards,
>
> Zooko
>
> >
> 

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