Fixed compilation issue with arena

src/arena_allocator.c

@@ -1,6 +1,5 @@
 #include "arena_allocator.h"
 #include <assert.h>
-#include <math.h>
 #include <stddef.h>
 #include <stdlib.h>
 
@@ -12,7 +11,7 @@ Arena arena_init(size_t capacity) {
 
 void arena_deinit(Arena *arena) {
   free(arena->data);
-  *arena = (Arena){.capacity = NAN, .size = 0, .data = NULL};
+  *arena = (Arena){.capacity = 0, .size = 0, .data = NULL};
 }
 
 void *arena_alloc(Arena *arena, size_t size) {

src/arena_allocator.h

@@ -5,7 +5,7 @@
 typedef struct {
   size_t capacity;
   size_t size;
-  void *data;
+  char *data;
 } Arena;
 
 Arena arena_init(size_t capacity);