util: replace memrchr with internal version

The amount of code we need to detect if this is present and handle
the fallback is more than if we just provide it ourselves.

Also we are passing in a difference of pointers so the argument
type should be ptrdiff_t. This avoids a C brain damage of having
unsigned size type which can wrap around if the caller is careful.

6 files changed, 19 insertions, 46 deletions

diff --git a/Makefile b/Makefile
index bdc1ba0..269d45f 100644
--- a/Makefile
+++ b/Makefile
@@ -52,11 +52,8 @@ CFLAGS_STD ?= -std=c99 -U_XOPEN_SOURCE -D_XOPEN_SOURCE=700 -DNDEBUG -MMD
 CFLAGS_STD += -DVERSION=\"${VERSION}\"
 LDFLAGS_STD ?= -lc
 
-CFLAGS_LIBC ?= -DHAVE_MEMRCHR=0
-
 CFLAGS_VIS = $(CFLAGS_AUTO) $(CFLAGS_TERMKEY) $(CFLAGS_CURSES) $(CFLAGS_ACL) \
-	$(CFLAGS_SELINUX) $(CFLAGS_TRE) $(CFLAGS_LUA) $(CFLAGS_LPEG) $(CFLAGS_STD) \
-	$(CFLAGS_LIBC)
+	$(CFLAGS_SELINUX) $(CFLAGS_TRE) $(CFLAGS_LUA) $(CFLAGS_LPEG) $(CFLAGS_STD)
 
 CFLAGS_VIS += -DVIS_PATH=\"${SHAREPREFIX}/vis\"
 CFLAGS_VIS += -DCONFIG_HELP=${CONFIG_HELP}
diff --git a/configure b/configure
index a70eac1..cc00cd7 100755
--- a/configure
+++ b/configure
@@ -613,25 +613,6 @@ EOF
 	fi
 fi
 
-printf "checking for memrchr... "
-
-cat > "$tmpc" <<EOF
-#define _GNU_SOURCE
-#include <string.h>
-
-int main(int argc, char *argv[]) {
-        return !memrchr("\n", '\n', 1);
-}
-EOF
-
-if $CC $CFLAGS $CFLAGS_STD "$tmpc" $LDFLAGS -o "$tmpo" >/dev/null 2>&1; then
-	HAVE_MEMRCHR=1
-	printf "%s\n" "yes"
-else
-	HAVE_MEMRCHR=0
-	printf "%s\n" "no"
-fi
-
 printf "completing config.mk... "
 
 exec 3>&1 1>>config.mk
@@ -659,7 +640,6 @@ LDFLAGS_ACL = $LDFLAGS_ACL
 CONFIG_SELINUX = $CONFIG_SELINUX
 CFLAGS_SELINUX = $CFLAGS_SELINUX
 LDFLAGS_SELINUX = $LDFLAGS_SELINUX
-CFLAGS_LIBC = -DHAVE_MEMRCHR=$HAVE_MEMRCHR
 EOF
 exec 1>&3 3>&-
 
diff --git a/test/core/Makefile b/test/core/Makefile
index b0284b8..5f1e965 100644
--- a/test/core/Makefile
+++ b/test/core/Makefile
@@ -16,19 +16,19 @@ config.h:
 
 text-test: config.h text-test.c ../../text.c ../../text-common.c ../../text-io.c ../../text-iterator.c ../../text-util.c ../../text-motions.c ../../text-objects.c ../../text-regex.c ../../array.c
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
 
 buffer-test: config.h buffer-test.c ../../buffer.c
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} buffer-test.c ${SRC} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} buffer-test.c ${SRC} ${LDFLAGS} -o $@
 
 map-test: config.h map-test.c ../../map.c
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
 
 array-test: config.h array-test.c ../../array.c
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} ${filter %.c, $^} ${SRC} ${LDFLAGS} -o $@
 
 debug: clean
 	$(MAKE) CFLAGS_EXTRA='${CFLAGS_EXTRA} ${CFLAGS_DEBUG}'
diff --git a/test/fuzz/Makefile b/test/fuzz/Makefile
index 9aade50..3b79ef1 100644
--- a/test/fuzz/Makefile
+++ b/test/fuzz/Makefile
@@ -10,15 +10,15 @@ test: $(ALL)
 
 text-fuzzer: text-fuzzer.c fuzzer.h $(TEXT_SRC)
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} ${filter %.c, $^} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} ${filter %.c, $^} ${LDFLAGS} -o $@
 
 text-libfuzzer: text-fuzzer.c fuzzer.h $(TEXT_SRC)
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} -DLIBFUZZER ${filter %.c, $^} -fsanitize=fuzzer,address,undefined ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} -DLIBFUZZER ${filter %.c, $^} -fsanitize=fuzzer,address,undefined ${LDFLAGS} -o $@
 
 buffer-fuzzer: buffer-fuzzer.c fuzzer.h ../../buffer.c
 	@echo Compiling $@ binary
-	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_LIBC} ${CFLAGS_EXTRA} ${filter %.c, $^} ${LDFLAGS} -o $@
+	@${CC} ${CFLAGS} ${CFLAGS_STD} ${CFLAGS_EXTRA} ${filter %.c, $^} ${LDFLAGS} -o $@
 
 debug: clean
 	$(MAKE) CFLAGS_EXTRA='${CFLAGS_EXTRA} ${CFLAGS_DEBUG}'
diff --git a/text-iterator.c b/text-iterator.c
index e080ca5..b61c609 100644
--- a/text-iterator.c
+++ b/text-iterator.c
@@ -1,6 +1,3 @@
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE /* memrchr(3) is non-standard */
-#endif
 #include <limits.h>
 #include <stddef.h>
 #include <errno.h>
@@ -72,9 +69,19 @@ bool text_iterator_byte_prev(Iterator *it, char *b) {
 	return true;
 }
 
+static void *scan_memory_reverse(const void *memory, int byte, ptrdiff_t n)
+{
+	void *result = 0;
+	if (n > 0) {
+		const signed char *s = memory;
+		while (n) if (s[--n] == byte) { result = (void *)(s + n); break; }
+	}
+	return result;
+}
+
 bool text_iterator_byte_find_prev(Iterator *it, char b) {
 	while (it->text) {
-		const char *match = memrchr(it->start, b, it->text - it->start);
+		const char *match = scan_memory_reverse(it->start, b, it->text - it->start);
 		if (match) {
 			it->pos -= it->text - match;
 			it->text = match;
diff --git a/util.h b/util.h
index 08a44a8..d84846a 100644
--- a/util.h
+++ b/util.h
@@ -23,17 +23,6 @@ static inline bool addu(size_t a, size_t b, size_t *c) {
 }
 #endif
 
-#if !HAVE_MEMRCHR
-/* MIT licensed implementation from musl libc */
-static void *memrchr(const void *m, int c, size_t n)
-{
-	const unsigned char *s = m;
-	c = (unsigned char)c;
-	while (n--) if (s[n]==c) return (void *)(s+n);
-	return 0;
-}
-#endif
-
 /* Needed for building on GNU Hurd */
 
 #ifndef PIPE_BUF