Add makefile and restructure

src/test_arena.c

@@ -0,0 +1,44 @@
+
+
+
+// _start test_arena_alloc.c
+#include "arena.h"
+#include <err.h>
+#include <stdio.h>
+#include <errno.h>
+
+static struct arena *default_arena = NULL;
+
+int main()
+{
+    default_arena = arena_new();
+
+    if (default_arena == NULL) {
+        err(errno, "failed to allocate arena");
+    }
+
+	printf("\n%p\n", default_arena->next);
+
+    char *ten_A = arena_alloc(default_arena, 11 * sizeof *ten_A);
+    char *ten_B = arena_alloc(default_arena, 11 * sizeof *ten_B);
+    char *ten_C = arena_alloc(default_arena, 11 * sizeof *ten_C);
+
+    for (size_t i=0; i<10; ++i) {
+        ten_A[i] = 'A';
+        ten_B[i] = 'B';
+        ten_C[i] = 'C';
+    }
+
+    ten_A[10] = '\0';
+    ten_B[10] = '\0';
+    ten_C[10] = '\0';
+
+    printf("\n%s %s %s", ten_A, ten_B, ten_C);
+	printf("\n%p\n", default_arena->next);
+
+	arena_reset(default_arena);
+
+	printf("\n%p\n", default_arena->next);
+
+    return 0;
+}