dev-perl/Digest-Nilsimsa: fix build w/ clang 16

Closes: https://bugs.gentoo.org/870895
Signed-off-by: Sam James <sam@gentoo.org>

dev-perl/Digest-Nilsimsa/Digest-Nilsimsa-0.60.0-r4.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2021 Gentoo Authors
+# Copyright 1999-2023 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
@@ -15,6 +15,10 @@ LICENSE="GPL-2+ LGPL-2"
 SLOT="0"
 KEYWORDS="~alpha amd64 ~hppa ~ia64 ppc ppc64 sparc x86 ~amd64-linux ~x86-linux ~ppc-macos"
 
+PATCHES=(
+	"${FILESDIR}"/${PN}-0.60.0-clang16.patch
+)
+
 src_compile() {
 	mymake=(
 		"OPTIMIZE=${CFLAGS}"

dev-perl/Digest-Nilsimsa/files/Digest-Nilsimsa-0.60.0-clang16.patch

@@ -0,0 +1,19 @@
+https://bugs.gentoo.org/870895
+https://rt.cpan.org/Public/Bug/Display.html?id=145874
+
+Add missing function prototypes.  This avoids implicit function
+declarations when building Nilsimsa.xs and build failures with future
+compilers.
+
+--- a/nilsimsa.h
++++ b/nilsimsa.h
+@@ -47,6 +47,8 @@ int nilsimsa(struct nsrecord *a,struct nsrecord *b);
+ void aggregate(int n);
+ void codetostr(struct nsrecord *a,char *str);
+ int strtocode(char *str,struct nsrecord *a);
++void makecode(struct nsrecord *a);
++void clear(struct nsrecord *a);
+ 
+ int accbuf(unsigned char *buf,int len,struct nsrecord *a);
+ void dprint(char *msg);
+