From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LqWKk-0002Th-AC for qemu-devel@nongnu.org; Sun, 05 Apr 2009 13:40:38 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LqWKj-0002Sd-62 for qemu-devel@nongnu.org; Sun, 05 Apr 2009 13:40:37 -0400 Received: from [199.232.76.173] (port=34508 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LqWKi-0002SD-TX for qemu-devel@nongnu.org; Sun, 05 Apr 2009 13:40:36 -0400 Received: from savannah.gnu.org ([199.232.41.3]:40623 helo=sv.gnu.org) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LqWKi-00044z-8N for qemu-devel@nongnu.org; Sun, 05 Apr 2009 13:40:36 -0400 Received: from cvs.savannah.gnu.org ([199.232.41.69]) by sv.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1LqWKh-00068N-4u for qemu-devel@nongnu.org; Sun, 05 Apr 2009 17:40:35 +0000 Received: from aliguori by cvs.savannah.gnu.org with local (Exim 4.69) (envelope-from ) id 1LqWKg-00068I-O7 for qemu-devel@nongnu.org; Sun, 05 Apr 2009 17:40:34 +0000 MIME-Version: 1.0 Errors-To: aliguori Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Anthony Liguori Message-Id: Date: Sun, 05 Apr 2009 17:40:34 +0000 Subject: [Qemu-devel] [6976] Document QEMU coding style (v2) (Avi Kivity) Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Revision: 6976 http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6976 Author: aliguori Date: 2009-04-05 17:40:34 +0000 (Sun, 05 Apr 2009) Log Message: ----------- Document QEMU coding style (v2) (Avi Kivity) With the help of some Limoncino I noted several aspects of the QEMU coding style, particularly where it differs from the Linux coding style as many contributors work on both projects. Signed-off-by: Avi Kivity Signed-off-by: Anthony Liguori Added Paths: ----------- trunk/CODING_STYLE Added: trunk/CODING_STYLE =================================================================== --- trunk/CODING_STYLE (rev 0) +++ trunk/CODING_STYLE 2009-04-05 17:40:34 UTC (rev 6976) @@ -0,0 +1,78 @@ +Qemu Coding Style +================= + +1. Whitespace + +Of course, the most important aspect in any coding style is whitespace. +Crusty old coders who have trouble spotting the glasses on their noses +can tell the difference between a tab and eight spaces from a distance +of approximately fifteen parsecs. Many a flamewar have been fought and +lost on this issue. + +QEMU indents are four spaces. Tabs are never used, except in Makefiles +where they have been irreversibly coded into the syntax by some moron. +Spaces of course are superior to tabs because: + + - You have just one way to specify whitespace, not two. Ambiguity breeds + mistakes. + - The confusion surrounding 'use tabs to indent, spaces to justify' is gone. + - Tab indents push your code to the right, making your screen seriously + unbalanced. + - Tabs will be rendered incorrectly on editors who are misconfigured not + to use tab stops of eight positions. + - Tabs are rendered badly in patches, causing off-by-one errors in almost + every line. + - It is the QEMU coding style. + +Do not leave whitespace dangling off the ends of lines. + +2. Line width + +Lines are 80 characters; not longer. + +Rationale: + - Some people like to tile their 24" screens with a 6x4 matrix of 80x24 + xterms and use vi in all of them. The best way to punish them is to + let them keep doing it. + - Code and especially patches is much more readable if limited to a sane + line length. Eighty is traditional. + - It is the QEMU coding style. + +3. Naming + +Variables are lower_case_with_underscores; easy to type and read. Structured +type names are in CamelCase; harder to type but standing out. Scalar type +names are lower_case_with_underscores_ending_with_a_t, like the POSIX +uint64_t and family. Note that this last convention contradicts POSIX +and is therefore likely to be changed. + +Typedefs are used to eliminate the redundant 'struct' keyword. It is the +QEMU coding style. + +4. Block structure + +Every indented statement is braced; even if the block contains just one +statement. The opening brace is on the line that contains the control +flow statement that introduces the new block; the closing brace is on the +same line as the else keyword, or on a line by itself if there is no else +keyword. Example: + + if (a == 5) { + printf("a was 5.\n"); + } else if (a == 6) { + printf("a was 6.\n"); + } else { + printf("a was something else entirely.\n"); + } + +An exception is the opening brace for a function; for reasons of tradition +and clarity it comes on a line by itself: + + void a_function(void) + { + do_something(); + } + +Rationale: a consistent (except for functions...) bracing style reduces +ambiguity and avoids needless churn when lines are added or removed. +Furthermore, it is the QEMU coding style.