[PATCH] checkpatch: Warn on self-assignments

From: Joe Perches
Date: Sat Sep 05 2020 - 13:58:38 EST


The uninitialized_var() macro was removed recently via
commit 63a0895d960a ("compiler: Remove uninitialized_var() macro")
as it's not a particularly useful warning and its use can
"paper over real bugs".

Add a checkpatch test to warn on self-assignments as a means
to avoid compiler warnings and as a back-door mechanism to
reproduce the old uninitialized_var macro behavior.

Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
---
scripts/checkpatch.pl | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 149518d2a6a7..300b2659aab3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3901,6 +3901,17 @@ sub process {
#ignore lines not being added
next if ($line =~ /^[^\+]/);

+# check for self assigments used to avoid compiler warnings
+# e.g.: int foo = foo, *bar = NULL;
+# struct foo bar = *(&(bar));
+ if ($line =~ /^\+\s*(?:$Declare)?([A-Za-z_][A-Za-z\d_]*)\s*=/) {
+ my $var = $1;
+ if ($line =~ /^\+\s*(?:$Declare)?$var\s*=\s*(?:$var|\*\s*\(?\s*&\s*\(?\s*$var\s*\)?\s*\)?)\s*[;,]/) {
+ WARN("SELF_ASSIGNMENT",
+ "Do not use self-assignments to avoid compiler warnings\n" . $herecurr);
+ }
+ }
+
# check for dereferences that span multiple lines
if ($prevline =~ /^\+.*$Lval\s*(?:\.|->)\s*$/ &&
$line =~ /^\+\s*(?!\#\s*(?!define\s+|if))\s*$Lval/) {