[Qgis-developer] Qgis plugin and typeid issues

[Emmanuel Christophe]

Hi all,

(sorry for double posting, the developer list seems more appropriate)

I'm working on the OTB (www.orfeo-toolbox.org) Qgis plugins: the
objective is to provide more raster processing capabilities to Qgis.
I run into a tricky C++ issue. In one particular case, one typeid
resolution does not seems to work. I believe that it is linked with
the issue mentioned here:

http://gcc.gnu.org/faq.html#dso
dynamic_cast, throw, typeid don't work with shared libraries

(I'm currently working with gcc and trying to make it work with shared
libraries).

What make me think that this is linked to this issue is that:
- the plugin is loaded using dlopen by qgis
- the typeid is created by some code compiled in the plugin (OTB uses
templates extensively, so this particular piece of OTB code is
compiled during the plugin compilation) and the resulting type_info is
passed to another dynamic library that was compiled before (during OTB
compilation).

So it seems that we are in the third case mentioned by the FAQ. In
this situation, the FAQ recommend to
"First, export global symbols from the executable by linking it with
the "-E" flag. You must also make the external symbols in the loaded
library available for subsequent libraries by providing the
RTLD_GLOBAL flag to dlopen. The symbol resolution can be immediate or
lazy."

The RTLD_GLOBAL flag seems to be provided
(src/app/qgspluginmanager.cpp:256), but I'm not sure about the -E flag
while linking. Can anybody with more experience in Qgis compilation
confirm?

Is there any other plugin I should look at for inspiration?

Emmanuel