path: root/Documentation/CodingStyle
diff options
authorDan Carpenter <>2014-12-02 11:59:50 +0300
committerJonathan Corbet <>2014-12-02 08:55:32 -0500
commitea04036032edda6f771c1381d03832d2ed0f6c31 (patch)
tree3266fb1cff71f9e52440d2710b5f6b03a8f3b8d7 /Documentation/CodingStyle
parent86d3e023e05d90b2b5f88dcbf2e334b5835131f8 (diff)
CodingStyle: add some more error handling guidelines
I added a paragraph on choosing label names, and updated the example code to use a better label name. I also cleaned up the example code to more modern style by moving the allocation out of the initializer and changing the NULL check. Perhaps the most common type of error handling bug in the kernel is "one err bugs". CodingStyle already says that we should "avoid nesting" by using error labels and one err style error handling tends to have multiple indent levels, so this was already bad style. But I've added a new paragraph explaining how to avoid one err bugs by using multiple error labels which is, hopefully, more clear. Signed-off-by: Dan Carpenter <> Acked-by: Julia Lawall <> [jc: added GFP_KERNEL to kmalloc() call] Signed-off-by: Jonathan Corbet <>
Diffstat (limited to 'Documentation/CodingStyle')
1 files changed, 22 insertions, 5 deletions
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 9f28b140dc89..618a33c940df 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -392,7 +392,12 @@ The goto statement comes in handy when a function exits from multiple
locations and some common work such as cleanup has to be done. If there is no
cleanup needed then just return directly.
-The rationale is:
+Choose label names which say what the goto does or why the goto exists. An
+example of a good name could be "out_buffer:" if the goto frees "buffer". Avoid
+using GW-BASIC names like "err1:" and "err2:". Also don't name them after the
+goto location like "err_kmalloc_failed:"
+The rationale for using gotos is:
- unconditional statements are easier to understand and follow
- nesting is reduced
@@ -403,9 +408,10 @@ The rationale is:
int fun(int a)
int result = 0;
- char *buffer = kmalloc(SIZE);
+ char *buffer;
- if (buffer == NULL)
+ buffer = kmalloc(SIZE, GFP_KERNEL);
+ if (!buffer)
return -ENOMEM;
if (condition1) {
@@ -413,14 +419,25 @@ int fun(int a)
result = 1;
- goto out;
+ goto out_buffer;
return result;
+A common type of bug to be aware of it "one err bugs" which look like this:
+ kfree(foo->bar);
+ kfree(foo);
+ return ret;
+The bug in this code is that on some exit paths "foo" is NULL. Normally the
+fix for this is to split it up into two error labels "err_bar:" and "err_foo:".
Chapter 8: Commenting
Comments are good, but there is also a danger of over-commenting. NEVER