Add the Clang specific -Wmissing-variable-declarations to WARNS=6.

This compiler flag enforces that that people either mark variables
static or use an external declarations for the variable, similar to how
-Wmissing-prototypes works for functions.

Due to the fact that Yacc/Lex generate code that cannot trivially be
changed to not warn because of this (lots of yy* variables), add a
NO_WMISSING_VARIABLE_DECLARATIONS that can be used to turn off this
specific compiler warning.

Announced on:	toolchain@

1 files changed, 2 insertions, 2 deletions

diff --git a/usr.bin/m4/Makefile b/usr.bin/m4/Makefile
index 1f1ec5e0f6de..f0e22f806c87 100644
--- a/usr.bin/m4/Makefile
+++ b/usr.bin/m4/Makefile
@@ -8,8 +8,8 @@ PROG=	m4
 CFLAGS+=-DEXTENDED -I${.CURDIR} -I${.CURDIR}/lib
 DPADD=	${LIBY} ${LIBL} ${LIBM}
 LDADD=	-ly -ll -lm
-# clang needs 1 while with gcc we can use 2
-#WARNS=	1
+
+NO_WMISSING_VARIABLE_DECLARATIONS=
 
 SRCS=	eval.c expr.c look.c main.c misc.c gnum4.c trace.c parser.y tokenizer.l
 .PATH: ${.CURDIR}/lib