Add implementation of memrchr

configure

@@ -12498,6 +12498,7 @@ for ac_func in \
   initgroups \
   localtime_r \
   mallopt \
+  memrchr \
   mkdirat \
   openat \
   pthread_sigmask \

configure.ac

@@ -1515,6 +1515,7 @@ AC_CHECK_FUNCS( \
   initgroups \
   localtime_r \
   mallopt \
+  memrchr \
   mkdirat \
   openat \
   pthread_sigmask \

src/include/autoconf.h.in

@@ -248,6 +248,9 @@
 /* Define to 1 if you have the <memory.h> header file. */
 #undef HAVE_MEMORY_H
 
+/* Define to 1 if you have the `memrchr' function. */
+#undef HAVE_MEMRCHR
+
 /* Define to 1 if you have the `mkdirat' function. */
 #undef HAVE_MKDIRAT
 

src/include/missing-h

@@ -132,6 +132,10 @@ int strncasecmp(char *s1, char *s2, int n);
 int strcasecmp(char *s1, char *s2);
 #endif
 
+#ifndef HAVE_MEMRCHR
+void *memrchr(const void *s, int c, size_t n);
+#endif
+
 #ifndef HAVE_STRSEP
 char *strsep(char **stringp, char const *delim);
 #endif

src/lib/util/missing.c

@@ -75,6 +75,24 @@ int strcasecmp(char *s1, char *s2)
 }
 #endif
 
+
+#ifndef HAVE_MEMRCHR
+/** GNU libc extension on some platforms
+ *
+ */
+void *memrchr(void const *s, int c, size_t n)
+{
+	uint8_t *p;
+
+	if (n == 0) return NULL;
+
+	memcpy(&p, &s, sizeof(p));	/* defeat const */
+	for (p += (n - 1); p >= (uint8_t const *)s; p--) if (*p == (uint8_t)c) return (void *)p;
+
+	return NULL;
+}
+#endif
+
 #ifndef HAVE_INET_ATON
 int inet_aton(char const *cp, struct in_addr *inp)
 {
@@ -478,4 +496,3 @@ char const *inet_ntop(int af, void const *src, char *dst, size_t cnt)
 	return NULL;		/* don't support IPv6 */
 }
 #endif
-