diff --git a/build32/Makefile b/build32/Makefile
index 862577a..97f02b4 100644
--- a/build32/Makefile
+++ b/build32/Makefile
@@ -38,7 +38,6 @@ SYS_OBJS = system/cpuid.o \
            system/xhci.o
 
 LIB_OBJS = lib/barrier.o \
-           lib/ctype.o \
            lib/div64.o \
            lib/print.o \
            lib/read.o \
diff --git a/build64/Makefile b/build64/Makefile
index 3346983..5e806fd 100644
--- a/build64/Makefile
+++ b/build64/Makefile
@@ -38,7 +38,6 @@ SYS_OBJS = system/cpuid.o \
            system/xhci.o
 
 LIB_OBJS = lib/barrier.o \
-           lib/ctype.o \
            lib/print.o \
            lib/read.o \
            lib/string.o \
diff --git a/lib/ctype.c b/lib/ctype.c
deleted file mode 100644
index cf06610..0000000
--- a/lib/ctype.c
+++ /dev/null
@@ -1,27 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-// Copyright (C) 2020 Martin Whitaker.
-
-#include "ctype.h"
-
-//------------------------------------------------------------------------------
-// Public Functions
-//------------------------------------------------------------------------------
-
-int toupper(int c)
-{
-    if (c >= 'a' && c <= 'z') {
-        return c + 'A' -'a';
-    } else {
-        return c;
-    }
-}
-
-int isdigit(int c)
-{
-    return c >= '0' && c <= '9';
-}
-
-int isxdigit(int c)
-{
-    return isdigit(c) || (toupper(c) >= 'A' && toupper(c) <= 'F');
-}
diff --git a/lib/ctype.h b/lib/ctype.h
index f153018..a695d8c 100644
--- a/lib/ctype.h
+++ b/lib/ctype.h
@@ -14,18 +14,31 @@
  * If c is a lower-case letter, returns its upper-case equivalent, otherwise
  * returns c. Assumes c is an ASCII character.
  */
-int toupper(int c);
+static inline int toupper(int c)
+{
+    if (c >= 'a' && c <= 'z') {
+        return c + 'A' -'a';
+    } else {
+        return c;
+    }
+}
 
 /**
  * Returns 1 if c is a decimal digit, otherwise returns 0. Assumes c is an
  * ASCII character.
  */
-int isdigit(int c);
+static inline int isdigit(int c)
+{
+    return c >= '0' && c <= '9';
+}
 
 /**
  * Returns 1 if c is a hexadecimal digit, otherwise returns 0. Assumes c is an
  * ASCII character.
  */
-int isxdigit(int c);
+static inline int isxdigit(int c)
+{
+    return isdigit(c) || (toupper(c) >= 'A' && toupper(c) <= 'F');
+}
 
 #endif // CTYPE_H
diff --git a/lib/string.c b/lib/string.c
index 89f0f8d..257b6ce 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -43,16 +43,6 @@ int memcmp(const void *s1, const void *s2, size_t n)
     return 0;
 }
 
-void *memcpy(void *dest, const void *src, size_t n)
-{
-    char *d = (char *)dest, *s = (char *)src;
-
-    for (size_t i = 0; i < n; i++) {
-        d[i] = s[i];
-    }
-    return dest;
-}
-
 void *memmove(void *dest, const void *src, size_t n)
 {
     char *d = (char *)dest, *s = (char *)src;
@@ -74,16 +64,6 @@ void *memmove(void *dest, const void *src, size_t n)
     return dest;
 }
 
-void *memset(void *s, int c, size_t n)
-{
-    char *d = (char *)s;
-
-    for (size_t i = 0; i < n; i++) {
-        d[i] = c;
-    }
-    return s;
-}
-
 size_t strlen(const char *s)
 {
     size_t len = 0;
diff --git a/lib/string.h b/lib/string.h
index 37bd392..b24e704 100644
--- a/lib/string.h
+++ b/lib/string.h
@@ -24,8 +24,9 @@ int memcmp(const void *s1, const void *s2, size_t n);
  * Copies n bytes from the memory area pointed to by src to the memory area
  * pointed to by dest and returns a pointer to dest. The memory areas must
  * not overlap.
+ * void *memcpy(void *dst, const void *src, size_t n);
  */
-void *memcpy(void *dst, const void *src, size_t n);
+#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
 
 /**
  * Copies n bytes from the memory area pointed to by src to the memory area
@@ -37,8 +38,9 @@ void *memmove(void *dest, const void *src, size_t n);
 /**
  * Fills the first n bytes of the memory area pointed to by s with the byte
  * value c.
+ * void *memset(void *s, int c, size_t n);
  */
-void *memset(void *s, int c, size_t n);
+#define memset(s, c, n) __builtin_memset((s), (c), (n))
 
 /**
  * Returns the string length, excluding the terminating null character.