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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/process/coding-style.rst | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst index 4e611a01adc6..8ea913e99fa1 100644 --- a/Documentation/process/coding-style.rst +++ b/Documentation/process/coding-style.rst @@ -938,7 +938,37 @@ result. Typical examples would be functions that return pointers; they use NULL or the ERR_PTR mechanism to report failure. -17) Don't re-invent the kernel macros +17) Using bool +-------------- + +The Linux kernel bool type is an alias for the C99 _Bool type. bool values can +only evaluate to 0 or 1, and implicit or explicit conversion to bool +automatically converts the value to true or false. When using bool types the +!! construction is not needed, which eliminates a class of bugs. + +When working with bool values the true and false definitions should be used +instead of 1 and 0. + +bool function return types and stack variables are always fine to use whenever +appropriate. Use of bool is encouraged to improve readability and is often a +better option than 'int' for storing boolean values. + +Do not use bool if cache line layout or size of the value matters, as its size +and alignment varies based on the compiled architecture. Structures that are +optimized for alignment and size should not use bool. + +If a structure has many true/false values, consider consolidating them into a +bitfield with 1 bit members, or using an appropriate fixed width type, such as +u8. + +Similarly for function arguments, many true/false values can be consolidated +into a single bitwise 'flags' argument and 'flags' can often be a more +readable alternative if the call-sites have naked true/false constants. + +Otherwise limited use of bool in structures and arguments can improve +readability. + +18) Don't re-invent the kernel macros ------------------------------------- The header file include/linux/kernel.h contains a number of macros that @@ -961,7 +991,7 @@ need them. Feel free to peruse that header file to see what else is already defined that you shouldn't reproduce in your code. -18) Editor modelines and other cruft +19) Editor modelines and other cruft ------------------------------------ Some editors can interpret configuration information embedded in source files, @@ -995,7 +1025,7 @@ own custom mode, or may have some other magic method for making indentation work correctly. -19) Inline assembly +20) Inline assembly ------------------- In architecture-specific code, you may need to use inline assembly to interface @@ -1027,7 +1057,7 @@ the next instruction in the assembly output: : /* outputs */ : /* inputs */ : /* clobbers */); -20) Conditional Compilation +21) Conditional Compilation --------------------------- Wherever possible, don't use preprocessor conditionals (#if, #ifdef) in .c |