TODO.md

• valgrind memtest
• generate docs from headers
• add unblocking select/poll support to fds (maybe in IO module?)
• (maybe?) set fd_assignment for a custom fd to -1 to prevent closing it in sp_free
• capturing return-code of programs terminating with signals (e.g. SIGSEGV) in sp_wait?
• move process.c-relevant header material into process.h and include it in subproc.h