On 27/04/2012 18:06, Marvin Humphrey wrote:
On Fri, Apr 27, 2012 at 5:36 AM, Nick Wellnhofer<[email protected]> wrote:
On 27/04/2012 14:22, Nick Wellnhofer wrote:
This leads me to question whether extensions should be linking against the
shared objects of their dependencies on *any* platform. Does that create a
tight binding that will e.g. break WhitespaceTokenizer when Lucy gets
updated? I'm pretty sure we want runtime relocation of upstream symbols.
On Linux I had to link against Lucy.so. Otherwise I get "undefined
symbol" errors when running the tests.
There seem to be two workarounds on Linux: Link the main executable with
-rdynamic or pass the RTLD_GLOBAL flag to dl_open. Since our main executable
is perl, the former won't work. But the latter can be achieved by using
DynaLoader with dl_load_flags set to 1.
Ah, it's *that* problem.
http://www.perlmonks.org/?node_id=691130
Dynaloader/XS: sharing C symbols across shared objects
I have two XS modules, and I would like C symbols loaded by one to be
accessible from the other. The ultimate goal is to avoid including the
Snowball stemming library in the KinoSearch distribution, with all of its
compilation overhead, but instead load Lingua::Stem::Snowball and its
associated shared object and have the Snowball C API be accessible from
within the KinoSearch shared object.
This works fine on Mac OS X, but not on FreeBSD or Linux.
The solution that came out of that discussion -- pass function pointer
addresses around via Perl scalars because that's guaranteed to work
everywhere -- isn't feasible here. Nevertheless, I'd hazard a guess from the
discussion of the dl_load_flags approach in that thread that if we go that
route we're all set for all common Unixy systems.
Yes, I think so.
Our next move, then, is to see whether we can make the extension work on
ActivePerl/MSVC, Strawberry Perl, and Cygwin.
The WhitespaceTokenizer extension works on ActivePerl/MSVC but we'll
have to keep using cf_linker_flags. This will also be the case for other
Perls on Windows, since the dynamic linker is part of the OS.
So I propose we switch to DynaLoader with dl_load_flags (this also helps
with the other XSLoader problem) and keep cf_linker_flags. It can simply
return an empty array on every platform but Windows.
Nick
