[PATCH V2] checkpatch: Flag code that returns a negative number less than 1

From: Nishanth Menon
Date: Fri Jun 03 2016 - 16:02:47 EST

In some functions, returning a -ve decimal value is actually a valid
return condition when the function is returning a value, however, it
can also be misused for returning an error value that should ideally
be a valid error code defined in include/uapi/asm-generic/errno-base.h
or include/uapi/asm-generic/errno.h. The notable exception is "-1"
which has quiet a history of usage as pointed out by Joe Perches.

Considering typical error of doing the following:
int fn(void)
/* ... error condition ... */
return -2;

void fn1(void)
/* some code */
if (fn() < 0) {
pr_err("Error occurred\n");
/* other cases... */

Flag this as a check case for developer verification.

The check is done for negative values less than 1 and tools
directory is exempt from this requirement based on Joe Perches'

Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Nishanth Menon <nm@xxxxxx>
Changes in V2:
- change in regex for check for check for less than 1
- Update in commit message to the effect
- Added Suggested-by for Joe's recommendation on regex.

V1: https://patchwork.kernel.org/patch/9153345/

scripts/checkpatch.pl | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 4904ced676d4..a2e677b5fd78 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4351,6 +4351,12 @@ sub process {

+# return with a value is not usually a good sign, unless the function is supposed to return a value
+ if ($realfile !~ /^tools/ && defined($stat) && $stat =~ /^.\s*return\s*-\s*(?!1\b)\d+\s*;/s) {
+ "Suspect error return with a value, If this is error value, refer to include/uapi/asm-generic/errno-base.h and include/uapi/asm-generic/errno.h\n" . $herecurr);
+ }
# unnecessary return in a void function
# at end-of-function, with the previous line a single leading tab, then return;
# and the line before that not a goto label target like "out:"