View source for Talk:L4Re error handling

= DRAFT =

* interresting files ./l4sys/include/err.h, ./l4util/include/assert.h, ./l4re/include/error_helper, ./l4sys/lib/src/errtostr.c, ./cxx/lib/util/src/ipc_error_str.cc, ./cxx/lib/base/include/exceptions, ./cxx/lib/base/include/std_exc_io, ./moe/server/src/exception.cc, ./moe/server/src/exception.h, many files containing "debug", ./l4sys/include/ARCH-*/kdebug.h

* BD: JDB, the kernel debugger, could be relevant in so far that you could mention <tt>enter_kdebug()</tt>.
** usage: enter_kdebug("some message which helps others to find this call and see some state");
** enters jdb, prints this message
** NO jdb documentation at this time and place (BD: do you mean there's no documentation available? The basics in [http://os.inf.tu-dresden.de/fiasco/doc/jdb.pdf http://os.inf.tu-dresden.de/fiasco/doc/jdb.pdf] are still valid.)

* common types which can represent error conditions: l4_cap_idx_t, Cap, l4_msgtag_t
* l4_cap_idx_t and Cap are very similar, cause Cap is a wrapper for l4_cap_idx_t
** can be invalid
** check l4_cap_idx_t with l4_is_invalid_cap and l4_is_valid_cap
** check Cap with L4::Cap_base::is_valid
** '''TODO''' where and when do we use L4::Cap_base::validate?
** how to handle? log! also: don't support the feature which needs access to this capability... generally this means end the task
* l4_msgtag_t
** some error conditions
** many methods to check for more or less specific errors
** '''TODO''' talk to someone, grep code
** [http://os.inf.tu-dresden.de/~l4check/l4re/doc/html/group__l4__msgtag__api.html Message Tag] l4_msgtag_has_error and more
** [http://os.inf.tu-dresden.de/~l4check/l4re/doc/html/group__l4__ipc__err__api.html Error handling] l4_ipc_error, l4_error and more specific ones, most specific seams to be l4_ipc_error_code
** how to handle: log! depends on specific error. often task configuration error, so end task or don't provide feature


* [http://os.inf.tu-dresden.de/~l4check/l4re/doc/html/group__l4cxx__exceptions.html C++ Exceptions]
** chksys for l4_msgtag_t and long
** chkcap for Cap<T>
** throw some L4::Base_exception
** has a method returning a "human readable" string! L4::Base_exception::str
** exceptions can be printed with std::ostream
** you can put try { } catch(e) { std::cerr << e } in your thread functions like main
** useful usage seen in mag/server/src/main.cc


* ./l4sys/lib/src/errtostr.c
** l4sys_errtostr(long) for L4_E* and L4_IPC_* constants
* ./cxx/lib/util/src/ipc_error_str.cc
** '''TODO''' too funny
* '''TODO''' grep for usage