eng: Move code formatting rules into one section

Clarify the 80 character limit.  Change the line continuation indent
level.

1 files changed, 196 insertions, 0 deletions

diff --git a/eng/coding-formatting.rst b/eng/coding-formatting.rst
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+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2018.
+.. COMMENT: RTEMS Foundation, The RTEMS Documentation Project
+
+Formatting
+**********
+
+Rules
+-----
+
+* Adhere to the :ref:`EightyCharacterLineLimit`.
+
+* Use spaces instead of tabs.
+
+* Use two spaces for one indentation level.
+
+* 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 parenthesis.
+
+* 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 white space at the end of a line.
+
+.. _EightyCharacterLineLimit:
+
+Eighty Character Line Limit
+---------------------------
+
+Code should look good for everyone under some standard width assumptions.
+Where a line wraps should be the same for anyone reading the code.  For
+historical reasons, RTEMS uses 80 characters as the maximum width for each line
+of code.  The newline (``\n``) character terminating the line does not count
+for the 80 character limit.
+
+If you find yourself with code longer than 80 characters, first ask yourself
+whether the nesting level is too deep, names too long, compound expressions too
+complicated, or if some other guideline for improving readability can help to
+shrink the line length.  Refactoring nested blocks into functions can help to
+alleviate code width problems while improving code readability.  Making names
+descriptive yet terse can also improve readability.  If absolutely necessary to
+have a long line, follow the rules on this page to break the line up to adhere
+to the 80 characters per line rule.
+
+Breaking Long Lines
+-------------------
+
+The ``if``, ``while``, and ``for`` control statements have their condition
+expressions aligned and broken on separate lines.  When the conditions have to
+be broken, none go on the first line with the ``if``, ``while``, or ``for``
+statement, and none go on the last line with the closing parenthesis and the
+curly brace.  Long statements are broken up and indented at operators, with an
+operator always being the last token on a line.  No blank spaces should be left
+at the end of any line.  The continuation of a broken line is indented by one
+level.  Here is an example with a ``for`` loop.
+
+.. code-block:: c
+
+  for ( initialization = statement; a + really + longish + statement + that + evaluates + to < a + boolean; another + statement ) {
+    some_variable = a + really + longish + statement + that + needs + two + lines + gets + indented + four + more + spaces + on + the + second + and + subsequent + lines + and + broken + up + at + operators;
+  }
+
+Should be replaced with
+
+.. code-block:: c
+
+  for (
+    initialization = statement;
+    a + really + longish + statement + that + evaluates + to <
+      a + boolean;
+    another + statement
+  ) {
+    some_variable = a + really + longish + statement + that + needs +
+      two + lines + gets + indented + four + more +
+      spaces + on + the + second + and + subsequent +
+      lines + and + broken + up + at + operators;
+  }
+
+Similarly,
+
+.. code-block:: c
+
+  if ( this + that < those && this + these < that && this + those < these && this < those && those < that ) {
+
+should be broken up like
+
+.. code-block:: c
+
+  if (
+    this + that < those &&
+    this + these < that &&
+    this + those < these &&
+    this < those &&
+    those < that
+  ) {
+
+Note that each expression that resolves to a boolean goes on its own line.
+Where you place the boolean operator is a matter of choice.
+
+When a line is long because of a comment at the end, move the comment to
+just before the line, for example
+
+.. code-block:: c
+
+  #define A_LONG_MACRO_NAME (AND + EXPANSION) /* Plus + a + really + long + comment */
+
+can be replaced with
+
+.. code-block:: c
+
+  /* Plus + a + really + long + comment */
+  #define A_LONG_MACRO_NAME (AND + EXPANSION)
+
+C Preprocessor macros need to be broken up with some care, because the
+preprocessor does not understand that it should eat newline characters. So
+
+.. code-block:: c
+
+  #define A_LONG_MACRO_NAME (AND + EXCESSIVELY + LONG + EXPANSION + WITH + LOTS + OF + EXTRA + STUFF + DEFINED)
+
+would become
+
+.. code-block:: c
+
+  #define A_LONG_MACRO_NAME ( \
+    AND + EXCESSIVELY + LONG + EXPANSION + WITH + LOTS + OF + EXTRA + STUFF + \
+    DEFINED \
+  )
+
+Notice that each line is terminated by a backslash.
+The backslash tells the preprocessor to eat the newline. Of course, if you have
+such a long macro, you should consider not using a macro.
+
+Function declarations can be broken up at each argument, for example
+
+.. code-block:: c
+
+  int this_is_a_function( int arg1, int arg2, int arg3, int arg4, int arg5, int arg6, int arg7, int arg8, int arg9 );
+
+would be broken up as
+
+.. code-block:: c
+
+  int this_is_a_function(
+    int arg1,
+    int arg2,
+    int arg3,
+    int arg4,
+    int arg5,
+    int arg6,
+    int arg7,
+    int arg8,
+    int arg9
+  );
+
+Excessively long comments should be broken up at a word boundary or somewhere
+that makes sense, for example
+
+.. code-block:: c
+
+  /* Excessively long comments should be broken up at a word boundary or somewhere that makes sense, for example */
+
+would be
+
+.. code-block:: c
+
+  /*
+   * Excessively long comments should be broken up at a word boundary or
+   * somewhere that makes sense, for example.
+   */
+
+Note that multiline comments have a single asterisk aligned with the asterisk
+in the opening ``/*``.  The closing ``*/`` should appear on a line by itself at
+the end.