diff --git a/libc/minilibc/string.c b/libc/minilibc/string.c
index 3eac377c7..a306016d2 100644
--- a/libc/minilibc/string.c
+++ b/libc/minilibc/string.c
@@ -21,17 +21,17 @@
 /* there is no strcpy and strcmp implementation in RT-Thread */
 char *strcpy(char *dest, const char *src)
 {
-	return rt_strncpy(dest, src, rt_strlen(src) + 1);
+	return (char *)rt_strncpy(dest, src, rt_strlen(src) + 1);
 }
 
 char *strncpy(char *dest, const char *src, rt_ubase_t n)
 {
-	return rt_strncpy(dest, src, n);
+	return (char *)rt_strncpy(dest, src, n);
 }
 
 char *strlcpy(char *dest, const char *src, rt_ubase_t n)
 {
-	return rt_strlcpy(dest, src, n);
+	return (char *)rt_strlcpy(dest, src, n);
 }
 
 int strcmp (const char *s1, const char *s2)
@@ -243,11 +243,14 @@ unsigned long simple_strtoul(const char *cp,char **endp,unsigned int base)
 		if (*cp == '0') {
 			base = 8;
 			cp++;
-			if ((*cp == 'x') && isxdigit(cp[1])) {
+			if ((toupper(*cp) == 'X') && isxdigit(cp[1])) {
 				cp++;
 				base = 16;
 			}
 		}
+	} else if (base == 16) {
+		if (cp[0] == '0' && toupper(cp[1]) == 'X')
+			cp += 2;
 	}
 	while (isxdigit(*cp) &&
 	       (value = isdigit(*cp) ? *cp-'0' : toupper(*cp)-'A'+10) < base) {
@@ -280,26 +283,29 @@ long simple_strtol(const char *cp,char **endp,unsigned int base)
  */
 unsigned long long simple_strtoull(const char *cp,char **endp,unsigned int base)
 {
-	unsigned long long result = 0,value;
+	unsigned long long result = 0, value;
 
-	if (!base) {
-		base = 10;
-		if (*cp == '0') {
-			base = 8;
+	if (*cp == '0') {
+		cp++;
+		if ((toupper(*cp) == 'X') && isxdigit (cp[1])) {
+			base = 16;
 			cp++;
-			if ((*cp == 'x') && isxdigit(cp[1])) {
-				cp++;
-				base = 16;
-			}
+		}
+		if (!base) {
+			base = 8;
 		}
 	}
-	while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp)
-	    ? toupper(*cp) : *cp)-'A'+10) < base) {
-		result = result*base + value;
+	if (!base) {
+		base = 10;
+	}
+	while (isxdigit (*cp) && (value = isdigit (*cp)
+				? *cp - '0'
+				: (islower (*cp) ? toupper (*cp) : *cp) - 'A' + 10) < base) {
+		result = result * base + value;
 		cp++;
 	}
 	if (endp)
-		*endp = (char *)cp;
+		*endp = (char *) cp;
 	return result;
 }