qcow2: Inform block layer about discard boundaries

[mirror_qemu.git] / CODING_STYLE

diff --git a/CODING_STYLE b/CODING_STYLE
index 4280945ff021d35f54d0a9b8c0214372c8fa8655..e7fde1500384a07300d53f8c1b14151d6716bed1 100644 (file)
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -31,7 +31,11 @@ Do not leave whitespace dangling off the ends of lines.
 
 2. Line width
 
-Lines are 80 characters; not longer.
+Lines should be 80 characters; try not to make them longer.
+
+Sometimes it is hard to do, especially when dealing with QEMU subsystems
+that use long function or symbol names.  Even in that case, do not make
+lines much longer than 80 characters.
 
 Rationale:
  - Some people like to tile their 24" screens with a 6x4 matrix of 80x24
@@ -39,6 +43,8 @@ Rationale:
    let them keep doing it.
  - Code and especially patches is much more readable if limited to a sane
    line length.  Eighty is traditional.
+ - The four-space indentation makes the most common excuse ("But look
+   at all that white space on the left!") moot.
  - It is the QEMU coding style.
 
 3. Naming
@@ -87,7 +93,26 @@ Furthermore, it is the QEMU coding style.
 
 5. Declarations
 
-Mixed declarations (interleaving statements and declarations within blocks)
-are not allowed; declarations should be at the beginning of blocks.  In other
-words, the code should not generate warnings if using GCC's
--Wdeclaration-after-statement option.
+Mixed declarations (interleaving statements and declarations within
+blocks) are generally not allowed; declarations should be at the beginning
+of blocks.
+
+Every now and then, an exception is made for declarations inside a
+#ifdef or #ifndef block: if the code looks nicer, such declarations can
+be placed at the top of the block even if there are statements above.
+On the other hand, however, it's often best to move that #ifdef/#ifndef
+block to a separate function altogether.
+
+6. Conditional statements
+
+When comparing a variable for (in)equality with a constant, list the
+constant on the right, as in:
+
+if (a == 1) {
+    /* Reads like: "If a equals 1" */
+    do_something();
+}
+
+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.