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Jan Beulich
6954c93e08
Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: George Dunlap <george.dunlap@citrix.com>
136 lines
3.6 KiB
Plaintext
136 lines
3.6 KiB
Plaintext
Coding Style for the Xen Hypervisor
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===================================
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The Xen coding style described below is the coding style used by the
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Xen hypervisor itself (xen/*) as well as various associated low-level
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libraries (e.g. tools/libxc/*).
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An exception is made for files which are imported from an external
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source. In these cases the prevailing coding style of the upstream
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source is generally used (commonly the Linux coding style).
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Other parts of the code base may use other coding styles, sometimes
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explicitly (e.g. tools/libxl/CODING_STYLE) but often implicitly (Linux
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coding style is fairly common). In general you should copy the style
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of the surrounding code. If you are unsure please ask.
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Indentation
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-----------
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Indenting uses spaces, not tabs - in contrast to Linux. An indent
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level consists of four spaces. Code within blocks is indented by one
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extra indent level. The enclosing braces of a block are indented the
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same as the code _outside_ the block. e.g.
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void fun(void)
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{
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/* One level of indent. */
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{
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/* A second level of indent. */
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}
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}
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White space
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-----------
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Space characters are used to spread out logical statements, such as in
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the condition of an if or while. Spaces are placed between the
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keyword and the brackets surrounding the condition, between the
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brackets and the condition itself, and around binary operators (except
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the structure access operators, '.' and '->'). e.g.
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if ( (wibble & wombat) == 42 )
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{
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...
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There should be no trailing white space at the end of lines (including
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after the opening /* of a comment block).
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Line Length
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-----------
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Lines should be less than 80 characters in length. Long lines should
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be split at sensible places and the trailing portions indented.
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User visible strings (e.g., printk() messages) should not be split so
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they can searched for more easily.
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Bracing
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-------
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Braces ('{' and '}') are usually placed on a line of their own, except
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for the do/while loop. This is unlike the Linux coding style and
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unlike K&R. do/while loops are an exception. e.g.:
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if ( condition )
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{
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/* Do stuff. */
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}
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else
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{
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/* Other stuff. */
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}
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while ( condition )
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{
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/* Do stuff. */
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}
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do {
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/* Do stuff. */
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} while ( condition );
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etc.
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Braces should be omitted for blocks with a single statement. e.g.,
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if ( condition )
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single_statement();
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Types
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-----
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Use basic C types and C standard mandated typedef-s where possible (and
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with preference in this order). This in particular means to avoid u8,
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u16, etc despite those types continuing to exist in our code base.
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Fixed width types should only be used when a fixed width quantity is
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meant (which for example may be a value read from or to be written to a
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register).
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Especially with pointer types, whenever the pointed to object is not
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(supposed to be) modified, qualify the pointed to type with "const".
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Comments
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--------
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Only C style /* ... */ comments are to be used. C++ style // comments
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should not be used. Multi-word comments should begin with a capital
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letter. Comments containing a single sentence may end with a full
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stop; comments containing several sentences must have a full stop
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after each sentence.
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Multi-line comment blocks should start and end with comment markers on
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separate lines and each line should begin with a leading '*'.
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/*
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* Example, multi-line comment block.
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*
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* Note beginning and end markers on separate lines and leading '*'.
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*/
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Emacs local variables
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---------------------
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A comment block containing local variables for emacs is permitted at
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the end of files. It should be:
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/*
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* Local variables:
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* mode: C
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* c-file-style: "BSD"
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* c-basic-offset: 4
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* indent-tabs-mode: nil
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* End:
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*/
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