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authorPritish Jain <pritishjain2001@gmail.com>2018-12-09 21:20:04 +0530
committerJoel Sherrill <joel@rtems.org>2018-12-17 18:45:50 -0600
commit75f24638b3fc10537644ba3f88025504d298cc2a (patch)
tree8c8d4cbeb9f7e0815a4505baa987770cdbd20646 /eng
parentcc826d74f34bacec4ea180614323ebc72035a40b (diff)
downloadrtems-docs-75f24638b3fc10537644ba3f88025504d298cc2a.tar.bz2
eng/coding-conventions.rst: Convert TBD to Rest Format (GCI 2018)
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.. COMMENT: COPYRIGHT (c) 2018.
.. COMMENT: RTEMS Foundation, The RTEMS Documentation Project
+.. COMMENT:TBD - Convert the following to Rest and insert into this file
+.. COMMENT:TBD - https://devel.rtems.org/wiki/Developer/Coding/Conventions
+
Coding Conventions
******************
-TBD - Convert the following to Rest and insert into this file
-TBD - https://devel.rtems.org/wiki/Developer/Coding/Conventions
+The style of RTEMS is generally consistent in the core areas.
+This page attempts to capture generally accepted practices.
+When in doubt, consult the code around you or look in cpukit/rtems.
+See the sister page `Doxygen Recommendations <https://devel.rtems.org/wiki/Developer/Coding/Doxygen>`_.
+for examples that illustrate style rules and Doxygen usage.
+
+Source Documentation
+--------------------
+
+* Use Doxygen according to our `Doxygen Recommendations <https://devel.rtems.org/wiki/Developer/Coding/Doxygen>`_..
+* Start each file with a brief description followed by a license.
+ See `Boilerplate File Header <https://devel.rtems.org/wiki/Developer/Coding/Boilerplate_File_Header>`_..
+* Use /* */ comments.
+* Use comments wisely within function bodies, to explain
+ or draw attention without being verbose.
+* Use English prose and strive for good grammar,
+ spelling, and punctuation.
+* Use TODO: with a comment to indicate code that needs improvement.
+ Make it clear what there is to do.
+* Use XXX or FIXME to indicate an error/bug/broken code.
+
+Licenses
+--------
+
+* The RTEMS `License <https://devel.rtems.org/wiki/TBR/Website/License>`_. is the typical
+ and preferred license.
+ * 2- and 3-clause BSD, MIT, and other OSI-approved non-copyleft licenses
+ that permit statically linking with the code of different licenses
+ are acceptable.
+ * GPL licensed code is NOT acceptable, neither is LGPL.
+ See `this blog post explanation <http://gedare-csphd.blogspot.com/2013/05/software-licenses-with-rtems.html>`_.
+ for more information.
+ * Advertising obligations are NOT acceptable, but restrictions are permissible.
+
+Language and Compiler
+---------------------
+
+* Use C99.
+* Treat warnings as errors: eliminate them.
+* Favor C, but when assembly language is required use inline
+ assembly if possible.
+* Do not use compiler extensions.
+* Use the RTEMS_macros defined in score/basedefs.h for abstracting
+ compiler-specific features.
+* Use NULL for the null pointer, and prefer to use explicit
+ checks against NULL, e.g.,
+
+ .. code-block:: c
+
+ if ( ptr != NULL )
+ instead of
+
+ .. code-block:: c
+
+ if ( !ptr )
+* Use explicit checks for bits in variables.
+ * Example 1: Use
+ .. code-block:: c
+
+ if ( XBITS == (var & XBITS) )
+ to check for a set of defined bits.
+ * Example 2: Use
+ .. code-block:: c
+
+ if ( (var & X_FLAGS) != 0) )
+ instead of
+ .. code-block:: c
+
+ if ( !!(var & X_FLAGS) )
+ to check for at least 1 defined bit in a set.
+* Use '(void) unused;' to mark unused parameters and set-but-unused
+ variables immediately after being set.
+* Do not put function prototypes in C source files, any global functions
+ should have a prototype in a header file and any private function
+ should be declared static.
+* Declare global variables in exactly one header file.
+ Define global variables in at most one source file.
+ Include the header file declaring the global variable as
+ the first include file if possible to make sure that the
+ compiler checks the declaration and definition and that
+ the header file is self-contained.
+* Do not cast arguments to any printf() or printk() variant.
+ Use <inttypes.h> PRI constants for the types supported there.
+ Use <rtems/inttypes.h> for the other POSIX and RTEMS types that
+ have PRI constants defined there. This increases the portability
+ of the printf() format.
+* Do not use the register keyword. It is deprecated since C++14.
+
+Formatting
+-----------
+
+* Use spaces instead of tabs.
+* Use two spaces for indentation, four spaces for
+ hanging indentation.
+* Adhere to a limit of `80 characters per line <https://devel.rtems.org/wiki/Developer/Coding/80_characters_per_line>`_..
+* Put function return types and names on one line if they fit.
+* Put function calls on one line if they fit.
+* No space between a function name or function-like macro and
+ the opening parens.
+* Put braces on the same line as and one space after the
+ conditional expression ends.
+* Put the opening brace of a function definition one line after
+ the closing parenthesis of its prototype.
+* Put a single space inside and outside of each parenthesis
+ of a conditional expression.
+ * Exception: never put a space before a closing semi-colon.
+* Put a single space before and after ternary operators.
+* Put a single space before and after binary operators.
+* Put no space between unary operators (e.g. *, &, !, ~, ++, --)
+ and their operands.
+* No spaces around dereferencing operators (-> and .).
+* Do not use more than one blank line in a row.
+* Do not use trailing whitespace at the end of a line.
+
+Readability
+------------
+
+* Understand and follow the `naming rules <https://devel.rtems.org/wiki/Developer/Coding/NamingRules>`_..
+* Use typedef to remove 'struct', but do not use typedef
+ to hide pointers or arrays.
+ * Exception: typedef can be used to simplify function pointer types.
+
+* Do not mix variable declarations and code.
+* Declare variables at the start of a block.
+* Only use primitive initialization of variables at their declarations.
+ Avoid complex initializations or function calls in variable declarations.
+* Do not put unrelated functions or data in a single file.
+* Do not declare functions inside functions.
+* Avoid deep nesting by using early exits e.g. return, break, continue.
+ * Parameter checking should be done first with early error returns.
+ * Avoid allocation and critical sections until error checking is done.
+ * For error checks that require locking, do the checks early after acquiring locks.
+ * Use of 'goto' requires good reason and justification.
+
+* Test and action should stay close together.
+* Avoid complex logic in conditional and loop statements.
+* Put conditional and loop statements on the line after the expression.
+* Favor inline functions to hide
+ `compile-time feature-conditioned compilation <https://devel.rtems.org/wiki/Developer/Coding/Compile-time_feature-conditioned_compilation>`_..
+* Define non-inline functions in a .c source file.
+* Declare all global (non-static) functions in a .h header file.
+* Declare and define inline functions in one place. Usually, this
+ is a *impl.h header file.
+* Declare and define static functions in one place. Usually, this is
+ toward the start of a .c file. Minimize forward declarations of
+ static functions.
+* Function declarations should include variable names.
+* Avoid excess parentheses. Learn the
+ `operator precedence <https://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence>`_. rules.
+* Always use parentheses with sizeof. This is an exception to the rule
+ about excess parentheses.
+
+Robustness
+-----------
+
+* Check all return statuses.
+* Validate input parameters.
+* Use debug assertions (assert).
+* Use const when appropriate for read-only function parameters
+ and compile-time constant values.
+* Do not hard code limits such as maximum instances into your code.
+* Prefer to use sizeof(variable) instead of sizeof(type).
+* Favor C automatic variables over global or static variables.
+* Use global variables only when necessary and ensure
+ atomicity of operations.
+* Do not shadow variables.
+* Avoid declaring large buffers or structures on the stack.
+* Avoid using zero (0) as a valid value. Memory often
+ defaults to being zero.
+* Favor mutual exclusion primitives over disabling preemption.
+* Avoid unnecessary dependencies, such as by not calling
+ ''printf()'' on error paths.
+* Avoid inline functions and macros with complicated logic
+ and decision points.
+* Prefer inline functions, enum, and const variables instead of CPP macros.
+* CPP macros should use a leading underscore for parameter
+ names and `avoid macro pitfalls <https://gcc.gnu.org/onlinedocs/cpp/Macro-Pitfalls.html#Macro-Pitfalls>`_..
+
+Portability
+-----------
+
+* Think portable! RTEMS supports a lot of target hardware.
+* For integer primitives, prefer to use precise-width integer
+ types from C99 stdint.h.
+* Write code that is 16-bit, 32-bit, and 64-bit friendly.
+
+Maintainability
+---------------
+
+* Minimize modifications to `third-party code <https://devel.rtems.org/wiki/Developer/Coding/ThirdPartyCode>`_..
+* Keep it simple! Simple code is easier to debug and easier to read than clever code.
+* Share code with other architectures, CPUs, and BSPs where possible.
+* Do not duplicate standard OS or C Library routines.
+
+Performance
+-----------
+
+* Prefer algorithms with the `lowest order of time and space <https://devel.rtems.org/wiki/FAQ/AlgorithmicComplexity>`_.
+ for fast, deterministic execution times with small memory footprints.
+* Understand the constraints of `real-time programming <https://devel.rtems.org/wiki/TBR/Review/Real-Time_Resources>`_..
+ Limit execution times in interrupt contexts and critical sections,
+ such as Interrupt and Timer Service Routines (TSRs).
+* Functions used only through function pointers should be declared
+ 'static inline' (RTEMS_INLINE_ROUTINE)
+* Prefer to ++preincrement instead of postincrement++.
+* Avoid using floating point except where absolutely necessary.
+
+Miscellaneous
+-------------
+
+* If you need to temporarily change the execution mode of a
+ task/thread, restore it.
+* If adding code to ''cpukit'' be sure the filename is unique since
+ all files under that directory get merged into a single library.
+
+Layering
+--------
+
+* TBD: add something about the dependencies and header file layering.
+* Understand the `RTEMS Software Architecture <https://devel.rtems.org/wiki/TBR/UserManual/RTEMS_Software_Architecture>'_.
+
+Exceptions to the Rules
+-----------------------
+
+* Minimize reformatting existing code in RTEMS unless the file undergoes
+ substantial non-style changes.
+* `Third-party code <https://devel.rtems.org/wiki/Developer/Coding/ThirdPartyCode>`_.
+ should not be reformatted to fit RTEMS style.
+ Exception: unmaintained third-party code adopted and
+ maintained by RTEMS may be reformatted, subject to the
+ above rules.
+
+Tools
+-----
+
+Some of the above can be assisted by tool support. Feel free to add
+more tools, configurations, etc here.
+
+* `Uncrustify <http://uncrustify.sourceforge.net/>`_.
+ Configuration for RTEMS:
+ `rtems.uncrustify <https://devel.rtems.org/attachment/wiki/Developer/Coding/Conventions/rtems.uncrustify>`_.