Issue #18722: Remove uses of the "register" keyword in C code.
diff --git a/Python/mystrtoul.c b/Python/mystrtoul.c
index 8a54cbf..725f07c 100644
--- a/Python/mystrtoul.c
+++ b/Python/mystrtoul.c
@@ -92,11 +92,11 @@
 **              exceptions - we don't check for them.
 */
 unsigned long
-PyOS_strtoul(register char *str, char **ptr, int base)
+PyOS_strtoul(char *str, char **ptr, int base)
 {
-    register unsigned long result = 0; /* return value of the function */
-    register int c;             /* current input character */
-    register int ovlimit;       /* required digits to overflow */
+    unsigned long result = 0; /* return value of the function */
+    int c;             /* current input character */
+    int ovlimit;       /* required digits to overflow */
 
     /* skip leading white space */
     while (*str && Py_ISSPACE(Py_CHARMASK(*str)))
@@ -213,7 +213,7 @@
         if (ovlimit > 0) /* no overflow check required */
             result = result * base + c;
         else { /* requires overflow check */
-            register unsigned long temp_result;
+            unsigned long temp_result;
 
             if (ovlimit < 0) /* guaranteed overflow */
                 goto overflowed;