Not all systems provide memrchr, example are some MacOS/OSX variants.

config.h.in

@@ -241,6 +241,8 @@
 
 #undef HAVE_MEMMEM
 
+#undef HAVE_MEMRCHR
+
 #undef HAVE_QSORT
 
 #undef HAVE_STRUPR

configure

@@ -8226,6 +8226,13 @@ then :
 
 fi
 
+ac_fn_c_check_func "$LINENO" "memrchr" "ac_cv_func_memrchr"
+if test "x$ac_cv_func_memrchr" = xyes
+then :
+  printf "%s\n" "#define HAVE_MEMRCHR 1" >>confdefs.h
+
+fi
+
 ac_fn_c_check_func "$LINENO" "getopt" "ac_cv_func_getopt"
 if test "x$ac_cv_func_getopt" = xyes
 then :

configure.ac

@@ -267,6 +267,7 @@ AC_LINK_IFELSE(
 )
 
 AC_CHECK_FUNCS([memmem])
+AC_CHECK_FUNCS([memrchr])
 AC_CHECK_FUNCS([getopt])
 AC_CHECK_FUNCS([getpwuid])
 AC_CHECK_FUNCS([popen])

stuff/Makefile

@@ -51,6 +51,7 @@ file.o: file.c \
 	../config.h \
 	../types.h \
 	../boot/psetting.h \
+	../stuff/compat.h \
 	../stuff/file.h
 	$(CC) $< -o $@ -c
 

stuff/compat-test.c

@@ -1,10 +1,15 @@
 #include "config.h"
 #include "types.h"
 
+#undef HAVE_MEMRCHR
+#define memrchr ocp_memrchr
+
 #include "compat.h"
 
 #include "compat.c"
 
+#undef memrchr
+
 #include <string.h>
 #include <unistd.h>
 
@@ -276,6 +281,32 @@ static int test_splitpath42 (void)
 	return failed;
 }
 
+int test_memrchr (const char *s, const char c, size_t n, const char *e, const char *d)
+{
+	char *r = ocp_memrchr (s, c, n);
+	printf("%s: %s\n", d, (r != e) ? "failed" : "ok");
+	return r != e;
+}
+
+int do_test_memchr (void)
+{
+	const char *ooo = "ooo";
+	const char *ofo = "ofo";
+
+	const char *oooo = "oooo";
+	const char *foobarfoo = "foobarfoo";
+
+	int retval = 0;
+	retval |= test_memrchr ("foo", 'a', 3, 0, "memrchr(\"foo\", 'a', 3) => NULL");
+	retval |= test_memrchr (ooo+1, 'o', 0, 0, "memrchr(\"ooo\" + 1, 'o', 0) => NULL");
+	retval |= test_memrchr (ooo+1, 'o', 1, ooo+1, "memrchr(\"ooo\" + 1, 'o') => \"ooo\" + 1");
+	retval |= test_memrchr (ofo+1, 'o', 1, 0, "memrchr(\"ofo\" + 1, 'o') => NULL");
+	retval |= test_memrchr (oooo+1, 'o', 2, oooo+2, "memrchr(\"oooo\" + 1, 'o') => \"oooo\" + 2");
+	retval |= test_memrchr (foobarfoo, 'r', 9, foobarfoo + 5, "memrchr(\"foobarfoo\", 'r') => \"rfoo\"");
+
+	return retval;
+}
+
 int main(int argc, char *argv[])
 {
 	int retval = 0;
@@ -284,6 +315,8 @@ int main(int argc, char *argv[])
 
 	retval |= test_splitpath42 ();
 
+	retval |= do_test_memchr ();
+
 	if (retval)
 	{
 		printf ("%sSomething failed%s\n", ANSI_COLOR_RED, ANSI_COLOR_RESET);

stuff/compat.h

@@ -10,6 +10,21 @@ void getext_malloc (const char *src, char **ext);
 extern int splitpath4_malloc(const char *src, char **drive, char **path, char **file, char **ext); /* returns non-zero on errors */
 extern int splitpath_malloc(const char *src, char **drive, char **path, char **filename); /* returns non-zero on errors */
 
+#ifndef HAVE_MEMRCHR
+static inline void *memrchr(const void *s, int c, size_t n)
+{
+	char c2 = c;
+	char *s2 = (char *)s + n - 1;
+	while (n--)
+	{
+		if (*s2 == c2) return s2;
+		s2--;
+	}
+
+	return 0;
+}
+#endif
+
 #ifndef HAVE_STRUPR
 #include <ctype.h>
 static inline char *strupr(char *src)

stuff/file.c

@@ -20,6 +20,7 @@
 #include "types.h"
 
 #include "boot/psetting.h"
+#include "stuff/compat.h"
 #include "stuff/file.h"
 
 struct osfile_cacheline_t