diff --git a/Makefile b/Makefile
index e1057de..997769c 100644
--- a/Makefile
+++ b/Makefile
@@ -102,6 +102,7 @@ screenshot: ## Take a screenshot of the qemu window
 clean:
 	$(RM) kernel $(asmobj) $(gasmobj) $(cobj) $(deps) $(cinc) fd.iso kernel.debug kernel.map $(docobj)
 	$(RM) -r isodir
+	$(MAKE) -C userspace clean
 
 .PHONY:
 	userspace screenshot
diff --git a/core/klibc.h b/core/klibc.h
index 8b59f20..3d6b13a 100644
--- a/core/klibc.h
+++ b/core/klibc.h
@@ -37,8 +37,8 @@ int vprintf(const char *format, va_list ap) __attribute__ ((__format__ (printf,
 int printf(const char *format, ...) __attribute__ ((__format__ (printf, 1, 2)));
 
 // Could be used after malloc is available
-int asprintf(char **strp, const char *fmt, ...);
-int vasprintf(char **strp, const char *fmt, va_list ap);
+int asprintf(char **strp, const char *fmt, ...) __attribute__ ((__format__ (printf, 2, 3)));
+int vasprintf(char **strp, const char *fmt, va_list ap) __attribute__ ((__format__ (printf, 2, 0)));
 
 /*
  * Dummy printk for disabled debugging statements to use whilst maintaining
diff --git a/userspace/libc.c b/userspace/libc.c
index 4b1dff0..991b192 100644
--- a/userspace/libc.c
+++ b/userspace/libc.c
@@ -80,6 +80,16 @@ void *memcpy(void *dst0, const void *src0, size_t len0)
 #endif
 }
 
+void *memmove(void *dst, const void *src, size_t n)
+{
+    char *dstChar       = dst;
+    const char *srcChar = src;
+    for (size_t i = 0; i < n; i++) {
+        *(dstChar++) = *(srcChar++);
+    }
+    return dst;
+}
+
 void *memset(void *src, int c, size_t n)
 {
     for (char *ptr = (char *)src; n > 0; n--, ptr++) {
@@ -602,20 +612,25 @@ struct heapBlock {
 
 static struct heapBlock *heapBlkList = NULL;
 
-struct heapBlock *findFreeBlock(size_t size){
-    struct heapBlock *cur = NULL;
+static struct heapBlock *findFreeBlock(size_t size)
+{
+    struct heapBlock *cur   = NULL;
     struct heapBlock *found = NULL;
     int idx;
-    list_foreach(heapBlkList, cur, idx){
-        if(cur->size >= size && cur->free){
+
+    list_foreach(heapBlkList, cur, idx)
+    {
+        if (cur->size >= size && cur->free) {
             found = cur;
             break;
         }
     }
+
     return found;
 }
 
-struct heapBlock *allocNewBlock(size_t size) {
+static struct heapBlock *allocNewBlock(size_t size)
+{
     struct heapBlock *blk  = sbrk(size + sizeof(struct heapBlock));
     struct heapBlock *head = sbrk(0);
     size_t blkSize         = (intptr_t)head - (intptr_t)blk - sizeof(struct heapBlock);
@@ -625,10 +640,11 @@ struct heapBlock *allocNewBlock(size_t size) {
     blk->size = blkSize;
     blk->free = 1;
     list_add_tail(heapBlkList, blk);
+
     return blk;
 }
 
-struct heapBlock *splitBlock(struct heapBlock *blk, size_t neededSize)
+static struct heapBlock *splitBlock(struct heapBlock *blk, size_t neededSize)
 {
     if (blk->size < neededSize + sizeof(struct heapBlock) + 1) {
         return NULL;
@@ -637,6 +653,7 @@ struct heapBlock *splitBlock(struct heapBlock *blk, size_t neededSize)
     newBlk->free             = 1;
     newBlk->size             = blk->size - sizeof(struct heapBlock) - neededSize;
     blk->size                = neededSize;
+
     return newBlk;
 }
 
@@ -655,16 +672,18 @@ void *malloc(size_t size)
         list_add_head(heapBlkList, remainBlock);
     }
     blk->free = 0;
+
     return blk + 1; // return the area after the blk description
 }
 
-struct heapBlock *getHeapBlock(void *ptr) {
+static struct heapBlock *getHeapBlock(void *ptr)
+{
     return (struct heapBlock *)ptr - 1;
 }
 
-
-void free(void *ptr){
-    if(!ptr)
+void free(void *ptr)
+{
+    if (!ptr)
         return;
 
     struct heapBlock *blk = getHeapBlock(ptr);
@@ -673,3 +692,36 @@ void free(void *ptr){
     blk->free = 1;
 }
 
+void *calloc(size_t nmemb, size_t size)
+{
+    size_t allocSize = nmemb * size;
+    void *ptr        = malloc(allocSize);
+
+    if (ptr != NULL)
+        memset(ptr, 0, allocSize);
+
+    return ptr;
+}
+
+void *realloc(void *ptr, size_t size)
+{
+    if (!ptr) {
+        return malloc(size);
+    }
+
+    struct heapBlock *blk = getHeapBlock(ptr);
+    if (blk->size >= size) {
+        return ptr;
+    }
+
+    void *new_ptr;
+    new_ptr = malloc(size);
+    if (!new_ptr) {
+        return NULL;
+    }
+    memmove(new_ptr, ptr, blk->size);
+    free(ptr);
+
+    return new_ptr;
+}
+
diff --git a/userspace/libc.h b/userspace/libc.h
index 4e2a4a5..eb4c313 100644
--- a/userspace/libc.h
+++ b/userspace/libc.h
@@ -14,8 +14,15 @@
 #define isprint(c) ((' ' <= (c)) && ((c) <= '~'))
 #define EOF (-1)
 
-
+/** compares the first @param n bytes (each interpreted as
+ *      unsigned char) of the memory areas @param s1 and @param s2.
+ */
 __attribute__ ((access (read_only, 1, 3), access (read_only, 2, 3))) int memcmp(const void *s1, const void *s2, size_t n);
+
+/**
+ * copies n bytes from memory area src to memory area dest. The memory areas may overlap
+ */
+__attribute__ ((access (write_only, 1, 3), access (read_only, 2, 3))) void *memmove(void *dest, const void *src, size_t n);
 __attribute__ ((access (write_only, 1, 3), access (read_only, 2, 3))) void *memcpy(void *dest, const void *src, size_t n);
 __attribute__ ((access (write_only, 1, 3))) void *memset(void *s, int c, size_t n);
 char *itoa(long long int value, char *str, int base);
@@ -51,4 +58,6 @@ int readline(char *buf, int size);
 int brk(void *addr);
 void *sbrk(intptr_t increment);
 void *malloc(size_t size);
+void *calloc(size_t nmemb, size_t size);
+void *realloc(void *ptr, size_t size);
 void free(void *ptr);