Accessing .so libraries using dlopen() throws undefined symbol error
linux, shared-libraries
Solution
Most likely, `libCamera.so` uses a symbol defined in a shared library without depending on that library.
Find a culprit. Take a real executable which links against `libCamera.so` (and it works). List its dependencies with `ldd /path/to/executable`. Among them should be a library which has a definition for `ZTVN10_cxxabiv117__class_type_infoE` (use `grep` to select likely candidates, `nm -D` on a library to be sure). That library won't be in the list shown by `ldd ./libCamera.so`.
Solve a problem. Load the library found in step 1 by `dlopen` first (use `RTLD_GLOBAL` there as well).
If there is a problem with another symbol, goto step 1.
If newly-added libraries have the same problem too, goto step 1.
Tell library authors to please fix their linking.
It could also happen that one of the prerequisites in `ldd ./libCamera.so` got upgraded and lost a symbol definition (maybe it was recompiled with a compiler which does name mangling differently). Then you won't find the culprit in step 1, and there is no solution but downgrading something again.
Problem
I'm trying to dynamically load a camera library .so file into a Linux executable to gain access to simple camera functions. I'm attempting to do this by: ``` if ( (newHandle = dlopen("./libCamera.so",RTLD_LAZY | RTLD_GLOBAL)) == NULL ) { printf( "Could not open file : %s\n", dlerror() ); return 1; } ``` However this fails and I receive the following output: "Could not open file : libCamera.so: undefined symbol: ZTVN10_cxxabiv117__class_type_infoE" How do I find out what symbols it is relying on?