[PATCH v3] scripts: coccicheck: Correct usage of make coccicheck

[Sumera Priyadarsini]

The command "make coccicheck C=1 CHECK=scripts/coccicheck" results in the
error:
        ./scripts/coccicheck: line 65: -1: shift count out of range

This happens because every time the C variable is specified,
the shell arguments need to be "shifted" in order to take only
the last argument, which is the C file to test. These shell arguments
mostly comprise flags that have been set in the Makefile. However,
when coccicheck is specified in the make command as a rule, the
number of shell arguments is zero, thus passing the invalid value -1
to the shift command, resulting in an error.

Modify coccicheck to print correct usage of make coccicheck so as to
avoid the error.

Signed-off-by: Sumera Priyadarsini <sylphrenadin@xxxxxxxxx>
---
Changes in v2:
- Move test to only display error message

Changes in v3:
- Update example with latest file
---
 scripts/coccicheck | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/scripts/coccicheck b/scripts/coccicheck
index 209bb0427b43..d1aaa1dc0a69 100755
--- a/scripts/coccicheck
+++ b/scripts/coccicheck
@@ -61,6 +61,18 @@ COCCIINCLUDE=${COCCIINCLUDE// -include/ --include}
 if [ "$C" = "1" -o "$C" = "2" ]; then
     ONLINE=1
 
+    if [[ $# -le 0 ]]; then
+	    echo ''
+	    echo 'Specifying both the variable "C" and rule "coccicheck" in the make
+command results in a shift count error.'
+	    echo ''
+	    echo 'Try specifying "scripts/coccicheck" as a value for the CHECK variable instead.'
+	    echo ''
+	    echo 'Example:	make C=2 CHECK=scripts/coccicheck drivers/net/ethernet/ethoc.o'
+	    echo ''
+	    exit 1
+    fi
+
     # Take only the last argument, which is the C file to test
     shift $(( $# - 1 ))
     OPTIONS="$COCCIINCLUDE $1"
-- 
2.25.1