diff options
| -rw-r--r-- | CODING_STYLE | 80 |
1 files changed, 63 insertions, 17 deletions
diff --git a/CODING_STYLE b/CODING_STYLE index c5f1e2e6c9..996897bcde 100644 --- a/CODING_STYLE +++ b/CODING_STYLE @@ -4,7 +4,8 @@ - Variables and functions *must* be static, unless they have a prototype, and are supposed to be exported. -- structs in MixedCase, variables + functions in lower_case +- structs in MixedCase (with exceptions, such as public API structs), + variables + functions in lower_case. - The destructors always unregister the object from the next bigger object, not the other way around @@ -22,30 +23,35 @@ more than one cause, it *really* should have "int" as return value for the error code. -- Don't bother with error checking if writing to stdout/stderr worked. +- Don't bother with error checking whether writing to stdout/stderr + worked. - Do not log errors from "library" code, only do so from "main - program" code. + program" code. (With one exception: it's OK to log with DEBUG level + from any code, with the exception of maybe inner loops). - Always check OOM. There's no excuse. In program code you can use - "log_oom()" for then printing a short message. + "log_oom()" for then printing a short message, but not in "library" code. - Do not issue NSS requests (that includes user name and host name - lookups) from the main daemon as this might trigger deadlocks when - those lookups involve synchronously talking to services that we - would need to start up + lookups) from PID 1 as this might trigger deadlocks when those + lookups involve synchronously talking to services that we would need + to start up -- Don't synchronously talk to any other service, due to risk of - deadlocks +- Don't synchronously talk to any other service from PID 1, due to + risk of deadlocks - Avoid fixed sized string buffers, unless you really know the maximum size and that maximum size is small. They are a source of errors, - since they result in strings to be truncated. Often it is nicer to - use dynamic memory, or alloca(). If you do allocate fixed size - strings on the stack, then it's probably only OK if you either use a - maximum size such as LINE_MAX, or count in detail the maximum size a - string can have. Or in other words, if you use "char buf[256]" then - you are likely doing something wrong! + since they possibly result in truncated strings. Often it is nicer + to use dynamic memory, alloca() or VLAs. If you do allocate fixed + size strings on the stack, then it's probably only OK if you either + use a maximum size such as LINE_MAX, or count in detail the maximum + size a string can have. (DECIMAL_STR_MAX and DECIMAL_STR_WIDTH + macros are your friends for this!) + + Or in other words, if you use "char buf[256]" then you are likely + doing something wrong! - Stay uniform. For example, always use "usec_t" for time values. Don't usec mix msec, and usec and whatnot. @@ -113,11 +119,51 @@ } - Use "goto" for cleaning up, and only use it for that. i.e. you may - only jump to the end of a function, and little else. + only jump to the end of a function, and little else. Never jump + backwards! - Think about the types you use. If a value cannot sensibly be negative don't use "int", but use "unsigned". - Don't use types like "short". They *never* make sense. Use ints, longs, long longs, all in unsigned+signed fashion, and the fixed - size types uint32_t and so on, but nothing else. + size types uint32_t and so on, as well as size_t but nothing else. + +- Public API calls (i.e. functions exported by our shared libraries) + must be marked "_public_" and need to be prefixed with "sd_". No + other functions should be prefixed like that. + +- In public API calls you *must* validate all your input arguments for + programming error with assert_return() and return a sensible return + code. In all other calls it is recommended to check for programming + errors with a more brutal assert(). We are more forgiving to public + users then for ourselves! Note that assert() and assert_return() + really only should be used for detecting programming errors, not for + runtime errors. assert() and assert_return() by usage of _likely_() + inform the compiler that he shouldn't expect these checks to fail, + and they inform fellow programmers about the expected validity and + range of parameters. + +- Never use strtol(), atoi() and similar calls. Use safe_atoli(), + safe_atou32() and suchlike instead. They are much nicer to use in + most cases and correctly check for parsing errors. + +- For every function you add, think about whether it is a "logging" + function or a "non-logging" function. "Logging" functions do logging + on their own, "non-logging" function never log on their own and + expect their callers to log. All functions in "library" code, + i.e. in src/shared/ and suchlike must be "non-logging". Everytime a + "logging" function calls a "non-logging" function it should log + about the resulting errors. If a "logging" function calls another + "logging" function, then it should not generate log messages, so + that log messages are not generated twice for the same errors. + +- Avoid static variables, except for caches and very few other + cases. Think about thread-safety! While most of our code is never + used in threaded environments at least the library code should make + sure it works correctly in them. Instead of doing a lot of locking + for that we tend to prefer using TLS to do per-thread caching (which + only works for small, fixed-size cache objects), or we disable + caching for any thread that is not the main thread. Use + is_main_thread() to detect whether the calling thread is the main + thread. |