virtio-net: Fix typo in comment

[mirror_qemu.git] / CODING_STYLE

diff --git a/CODING_STYLE b/CODING_STYLE
index e7fde1500384a07300d53f8c1b14151d6716bed1..ec075dedc4a89196bb1b0fa80223dcc83726a57a 100644 (file)
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -9,7 +9,7 @@ patches before submitting.
 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
+of approximately fifteen parsecs.  Many a flamewar has been fought and
 lost on this issue.
 
 QEMU indents are four spaces.  Tabs are never used, except in Makefiles
@@ -116,3 +116,62 @@ if (a == 1) {
 Rationale: Yoda conditions (as in 'if (1 == a)') are awkward to read.
 Besides, good compilers already warn users when '==' is mis-typed as '=',
 even when the constant is on the right.
+
+7. Comment style
+
+We use traditional C-style /* */ comments and avoid // comments.
+
+Rationale: The // form is valid in C99, so this is purely a matter of
+consistency of style. The checkpatch script will warn you about this.
+
+Multiline comment blocks should have a row of stars on the left,
+and the initial /* and terminating */ both on their own lines:
+    /*
+     * like
+     * this
+     */
+This is the same format required by the Linux kernel coding style.
+
+(Some of the existing comments in the codebase use the GNU Coding
+Standards form which does not have stars on the left, or other
+variations; avoid these when writing new comments, but don't worry
+about converting to the preferred form unless you're editing that
+comment anyway.)
+
+Rationale: Consistency, and ease of visually picking out a multiline
+comment from the surrounding code.
+
+8. trace-events style
+
+8.1 0x prefix
+
+In trace-events files, use a '0x' prefix to specify hex numbers, as in:
+
+some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
+
+An exception is made for groups of numbers that are hexadecimal by
+convention and separated by the symbols '.', '/', ':', or ' ' (such as
+PCI bus id):
+
+another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
+
+However, you can use '0x' for such groups if you want. Anyway, be sure that
+it is obvious that numbers are in hex, ex.:
+
+data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
+
+Rationale: hex numbers are hard to read in logs when there is no 0x prefix,
+especially when (occasionally) the representation doesn't contain any letters
+and especially in one line with other decimal numbers. Number groups are allowed
+to not use '0x' because for some things notations like %x.%x.%x are used not
+only in Qemu. Also dumping raw data bytes with '0x' is less readable.
+
+8.2 '#' printf flag
+
+Do not use printf flag '#', like '%#x'.
+
+Rationale: there are two ways to add a '0x' prefix to printed number: '0x%...'
+and '%#...'. For consistency the only one way should be used. Arguments for
+'0x%' are:
+ - it is more popular
+ - '%#' omits the 0x for the value 0 which makes output inconsistent