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authorDavid Herrmann <dh.herrmann@gmail.com>2015-09-05 13:03:59 +0200
committerDavid Herrmann <dh.herrmann@gmail.com>2015-09-05 18:24:26 +0200
commit54c1f2d761b506132a709a7e8573c7b54d048cf0 (patch)
treea276c14d170b80ca0d7f8accd366975535b07bd2
parent335250e7bdd09794f9a639c99fbd73b701b2d6e1 (diff)
CODING_STYLE: mandate alphabetical include order
systemd-internal headers must not rely on include order. That means, they either must contain forward-declarations of used types/functions, or they must include all dependencies on their own. Therefore, there is no reason to mandate an include order on the call-side. However, global includes should always be ordered first. We don't want local definitions to leak into global includes, possible changing their behavior. Apparently, namespacing is a complex problem that people are incapable of implementing properly.. Apart from "global before local", there is no reason to mandate a random include order (which we happen to do right now). Instead, mandate alphabetical ordering. The current rules do not have any benefit at all. They neither reduce include-complexity, nor allow easy auditing of include files. But with alphabetical ordering, we get duplicate-detection for free, it gets *much much* easier to figure out whether a header is already included, and it is trivial to add new headers.
-rw-r--r--CODING_STYLE28
1 files changed, 9 insertions, 19 deletions
diff --git a/CODING_STYLE b/CODING_STYLE
index a96ddd3598..f13f9becbc 100644
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -295,25 +295,15 @@
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