Zeuthen: Writing a C library, part 1

This is actually a common thing to encounter when using existing libraries in a single process embedded system. Different threads may be completely independent logically but both use a library which has a single global state.

If you are lucky, the library keeps all this data in a structure so you can use what are often called "per task variables" in an RTOS. This adds the contents of a global pointer to the context of a thread. It is then switched in and out with the thread. RTEMS and VxWorks both have these.

In a similar vein, reusing existing libraries used to dynamically
linked, multi-process environments to a single process, statically linked environment can also lead to symbol name conflicts when global symbols have common names.