The kbuild function if_changed should not be called more than once for
a target.
Because that function writes the command line to a .cmd file for later
tests, multiple calls of it within a target would result in overwrites
of previous values and effectively render the command line test
meaningless, resulting in flip-flop behaviour.
Add a check for makefiles and kbuild files and produce an error for
targets with multiple calls to if_changed.
Three examples that now could be detected:
98f78525371b55ccd (x86/boot: Refuse to build with data relocations)
6a8dfe1cac5c591ae (microblaze: support U-BOOT image format)
684151a75bf25f5ae (sparc32: added U-Boot build target: uImage)
Reviewed-by: Joe Perches <joe@xxxxxxxxxxx>
Suggested-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Signed-off-by: Dirk Gouders <dirk@xxxxxxxxxxx>
---
v2: rework commit message and regular expression
---
scripts/checkpatch.pl | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 447857ffaf6b..437e98414f74 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2911,6 +2911,14 @@ sub process {
"Use of $flag is deprecated, please use \`$replacement->{$flag} instead.\n" . $herecurr) if ($replacement->{$flag});
}
+ # Check for multiple calls of if_changed within a target in Makefiles
+ if (($realfile =~ /Makefile.*/ || $realfile =~ /Kbuild.*/) &&
+ ($prevline =~ /^[ +]\t\s*\$\(call\s+if_changed,/) &&
+ ($line =~ /^[ +]\t\s*\$\(call\s+if_changed,/)) {
+ ERROR("MULTIPLE_IF_CHANGED",
+ "Multiple calls of if_changed within a target.\n" . $herecurr);
+ }
+
# check for DT compatible documentation
if (defined $root &&
(($realfile =~ /\.dtsi?$/ && $line =~ /^\+\s*compatible\s*=\s*\"/) ||
--
2.16.1
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