Compiling a shared library

To compile a shared library that uses static linking:

1. Compile each source file into an object file, with no linking. For example:

   xlc -c foo.c -o foo.o

2. Optionally, create an export file listing the global symbols to be exported, by doing one of the following:
   • Use the CreateExportList utility, described in Exporting symbols with the CreateExportList utility.
   • Use the -qexpfile compiler option with the -qmkshrobj option, to create the basis for the export file used in the real link step. For example:

     xlc -qmkshrobj -qexpfile=exportlist foo.o

   • Manually create the export file. If necessary, in a text editor, edit the export file to control which symbols will be exported when you create the shared library.
3. Create the shared library from the desired object files, using the -qmkshrobj compiler option and the -bE linker option if you created an export file in step 2. If you do not specify a -bE option, all symbols will be exported. (If you are creating a shared library from C++ object files, you can also assign an initialization priority to the shared library, as described in Assigning priorities to objects.) For example:

   xlc -qmkshrobj foo.o -o mySharedObject -bE:exportlist

   (The default name of the shared object is shr.o, unless you use the -o option to specify another name.)

   Alternatively, if you are creating a shared library from C++ object files you can use the makeC++SharedLib utility, described in Creating a shared library with the makeC++SharedLib utility; however, the -qmkshrobj method is preferred as it has several advantages, including the ability to automatically handle C++ template instantiation, and compatibility with the -O5 optimization option.

4. Optionally, use the AIX® ar command to produce an archive library file from multiple shared or static objects. For example:

   ar -rv libfoo.a shr.o anotherlibrary.so

5. Link the shared library to the main application, as described in Linking a library to an application.

To create a shared library that uses runtime linking:

1. Follow steps 1 and 2 in the procedure described above.
2. Use the -G option to create a shared library from the generated object files, to be linked at load-time, and the -bE linker option to specify the name of the export list file. (You can also use the -qmkshrobj option if you want to specify a priority for a C++ shared object; see Initializing static objects in libraries (C++).) For example:

   xlc -G -o libfoo.so foo1.o foo2.o -bE:exportlist  

3. Link the shared library to the main application, as described in Linking a library to an application.

If you want the system to perform static initialization when dynamically loading a shared library, use the load and unload functions described in Dynamically loading a shared library.

>>-CreateExportList--+-----+--exp_list--+- -f--file_list-+--+-----+--+-------------+-><
                     '- -r-'            '-obj_files------'  '- -w-'  |      .-32-. |   
                                                                     '- -X--+-64-+-'