--- a/src/string.c	Thu Oct 02 17:58:43 2025 +0200
+++ b/src/string.c	Thu Oct 02 21:21:45 2025 +0200
@@ -25,14 +25,13 @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
+#ifdef MEMRCHR_NEED_GNU
 #define _GNU_SOURCE
-#include <string.h>
-#if defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >=2
-#define FEATURE_MEMRCHR_AVAILABLE
 #endif
 
 #include "cx/string.h"
 
+#include <string.h>
 #include <stdarg.h>
 #include <assert.h>
 #include <errno.h>
@@ -239,7 +238,7 @@
     cxstring string,
     int chr
 ) {
-#ifdef FEATURE_MEMRCHR_AVAILABLE
+#ifdef WITH_MEMRCHR
     char *ret = memrchr(string.ptr, 0xFF & chr, string.length);
     if (ret == NULL) return (cxstring) {NULL, 0};
     return (cxstring) {ret, string.length - (ret - string.ptr)};
@@ -248,7 +247,6 @@
     size_t i = string.length;
     while (i > 0) {
         i--;
-        // TODO: improve by comparing multiple bytes at once
         if (string.ptr[i] == chr) {
             return cx_strsubs(string, i);
         }