EXIT_FAILURE and EXIT_SUCCESS as defined by libc.
- The order in which header files are included doesn't matter too
- much. However, please try to include the headers of external
- libraries first (these are all headers enclosed in <>), followed by
- the headers of our own public headers (these are all headers
- starting with "sd-"), internal utility libraries from src/shared/,
- followed by the headers of the specific component. Or in other
- words:
-
- #include <stdio.h>
- #include "sd-daemon.h"
- #include "util.h"
- #include "frobnicator.h"
-
- Where stdio.h is a public glibc API, sd-daemon.h is a public API of
- our own, util.h is a utility library header from src/shared, and
- frobnicator.h is an placeholder name for any systemd component. The
- benefit of following this ordering is that more local definitions
- are always defined after more global ones. Thus, our local
- definitions will never "leak" into the global header files, possibly
- altering their effect due to #ifdeffery.
+ much. systemd-internal headers must not rely on an include order, so
+ it is safe to include them in any order possible.
+ However, to not clutter global includes, and to make sure internal
+ definitions will not affect global headers, please always include the
+ headers of external components first (these are all headers enclosed
+ in <>), followed by our own exported headers (usually everything
+ that's prefixed by "sd-"), and then followed by internal headers.
+ Furthermore, in all three groups, order all includes alphabetically
+ so duplicate includes can easily be detected.
- To implement an endless loop, use "for (;;)" rather than "while
(1)". The latter is a bit ugly anyway, since you probably really
always-true expression for an infinite while() loop is our
recommendation is to simply write it without any such expression by
using "for (;;)".
+
+- Never use the "off_t" type, and particularly avoid it in public
+ APIs. It's really weirdly defined, as it usually is 64bit and we
+ don't support it any other way, but it could in theory also be
+ 32bit. Which one it is depends on a compiler switch chosen by the
+ compiled program, which hence corrupts APIs using it unless they can
+ also follow the program's choice. Moreover, in systemd we should
+ parse values the same way on all architectures and cannot expose
+ off_t values over D-Bus. To avoid any confusion regarding conversion
+ and ABIs, always use simply uint64_t directly.
+
+- Commit message subject lines should be prefixed with an appropriate
+ component name of some kind. For example "journal: ", "nspawn: " and
+ so on.
+
+- Do not use "Signed-Off-By:" in your commit messages. That's a kernel
+ thing we don't do in the systemd project.
+
+- Avoid leaving long-running child processes around, i.e. fork()s that
+ are not followed quickly by an execv() in the child. Resource
+ management is unclear in this case, and memory CoW will result in
+ unexpected penalties in the parent much much later on.
+
+- Don't block execution for arbitrary amounts of time using usleep()
+ or a similar call, unless you really know what you do. Just "giving
+ something some time", or so is a lazy excuse. Always wait for the
+ proper event, instead of doing time-based poll loops.
+
+- To determine the length of a constant string "foo", don't bother
+ with sizeof("foo")-1, please use strlen("foo") directly. gcc knows
+ strlen() anyway and turns it into a constant expression if possible.
~ianmdlvl / elogind.git / blobdiff