21 Nov
2007
21 Nov
'07
7 a.m.
On Wed, 2007-11-21 at 02:57 +0000, james jwm-art net wrote:
Hi,
I'm attempting to use dlsym to dynamically load a ladspa plugin lib in
c++. I've found various web pages describing how to use dlsym in c++
but they do not seem entirely relevant to using ladspa (ie ladspa
plugins are mainly written in c) (??).
The LADSPA interface is defined in terms of C structures and types, so
the language used to write the plugin doesn't matter to the loader.
dlsym() is what you use. Strictly speaking it should not work in a
standards-compliant compiler without some ugly tricks since casting void
pointers (which is what dlsym() returns) to function pointers is not
allowed in C++, but fortunatly most compilers are not that strict about
it.
If you really want your code to work in a strict compiler you can do
something like
union {
void* in;
LADSPA_Descriptor_Function out;
} foo;
foo.in = dlsym(lib_handle, "ladspa_descriptor");
LADSPA_Descriptor* descriptor = (*foo.out)(0);
...
which will not generate any errors, but _will_ invoke undefined
behaviour. It works on all platforms I've tried though.
--ll