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author | Jonathan Corbet <corbet@lwn.net> | 2014-11-24 20:50:40 +0300 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2014-11-24 20:50:40 +0300 |
commit | 86d3e023e05d90b2b5f88dcbf2e334b5835131f8 (patch) | |
tree | 7695c67ca0ae65bbe04f7b6d7f244ab395f8dabc | |
parent | 690b0543a813b0ecfc51b0374c0ce6c8275435f0 (diff) | |
parent | 3c415707b37f1e4483c418c77f57692b89bcfd5e (diff) | |
download | linux-86d3e023e05d90b2b5f88dcbf2e334b5835131f8.tar.xz |
Merge branch 'docs-3.19' into docs-next
-rw-r--r-- | Documentation/CodingStyle | 43 | ||||
-rw-r--r-- | Documentation/kselftest.txt (renamed from tools/testing/selftests/README.txt) | 30 |
2 files changed, 62 insertions, 11 deletions
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle index 3171822c22a5..9f28b140dc89 100644 --- a/Documentation/CodingStyle +++ b/Documentation/CodingStyle @@ -845,6 +845,49 @@ next instruction in the assembly output: : /* outputs */ : /* inputs */ : /* clobbers */); + Chapter 20: Conditional Compilation + +Wherever possible, don't use preprocessor conditionals (#if, #ifdef) in .c +files; doing so makes code harder to read and logic harder to follow. Instead, +use such conditionals in a header file defining functions for use in those .c +files, providing no-op stub versions in the #else case, and then call those +functions unconditionally from .c files. The compiler will avoid generating +any code for the stub calls, producing identical results, but the logic will +remain easy to follow. + +Prefer to compile out entire functions, rather than portions of functions or +portions of expressions. Rather than putting an ifdef in an expression, factor +out part or all of the expression into a separate helper function and apply the +conditional to that function. + +If you have a function or variable which may potentially go unused in a +particular configuration, and the compiler would warn about its definition +going unused, mark the definition as __maybe_unused rather than wrapping it in +a preprocessor conditional. (However, if a function or variable *always* goes +unused, delete it.) + +Within code, where possible, use the IS_ENABLED macro to convert a Kconfig +symbol into a C boolean expression, and use it in a normal C conditional: + + if (IS_ENABLED(CONFIG_SOMETHING)) { + ... + } + +The compiler will constant-fold the conditional away, and include or exclude +the block of code just as with an #ifdef, so this will not add any runtime +overhead. However, this approach still allows the C compiler to see the code +inside the block, and check it for correctness (syntax, types, symbol +references, etc). Thus, you still have to use an #ifdef if the code inside the +block references symbols that will not exist if the condition is not met. + +At the end of any non-trivial #if or #ifdef block (more than a few lines), +place a comment after the #endif on the same line, noting the conditional +expression used. For instance: + +#ifdef CONFIG_SOMETHING +... +#endif /* CONFIG_SOMETHING */ + Appendix I: References diff --git a/tools/testing/selftests/README.txt b/Documentation/kselftest.txt index 2660d5ff9179..a87d840bacfe 100644 --- a/tools/testing/selftests/README.txt +++ b/Documentation/kselftest.txt @@ -15,37 +15,45 @@ Running the selftests (hotplug tests are run in limited mode) ============================================================= To build the tests: - $ make -C tools/testing/selftests To run the tests: - $ make -C tools/testing/selftests run_tests +To build and run the tests with a single command, use: + $ make kselftest + - note that some tests will require root privileges. -To run only tests targeted for a single subsystem: (including -hotplug targets in limited mode) - $ make -C tools/testing/selftests TARGETS=cpu-hotplug run_tests +Running a subset of selftests +======================================== +You can use the "TARGETS" variable on the make command line to specify +single test to run, or a list of tests to run. + +To run only tests targeted for a single subsystem: + $ make -C tools/testing/selftests TARGETS=ptrace run_tests + +You can specify multiple tests to build and run: + $ make TARGETS="size timers" kselftest + +See the top-level tools/testing/selftests/Makefile for the list of all +possible targets. -See the top-level tools/testing/selftests/Makefile for the list of all possible -targets. Running the full range hotplug selftests ======================================== -To build the tests: - +To build the hotplug tests: $ make -C tools/testing/selftests hotplug -To run the tests: - +To run the hotplug tests: $ make -C tools/testing/selftests run_hotplug - note that some tests will require root privileges. + Contributing new tests ====================== |