well, nothing works, at least there is something to debug

src/main.c

@@ -1,7 +1,17 @@
+#include "lexer.h"
+#include "parser.h"
 #include <stdlib.h>
 #include <stdio.h>
 
-int main(int argc, char *argv[]) {
-    puts("Hello");
+int main(void) {
+    ASTNodeArray context;
+
+    tokenize("3 + 4 * 5", &context);
+
+    AST tree = parse(&context);
+    print_AST(tree);
+
+    printf("Hola\n");
+
     return EXIT_SUCCESS;
 }

src/parser.c

@@ -107,7 +107,9 @@ void print_AST(AST tree) {
 }
 
 void print_node(ASTNode *node, int depth) {
-    if (!node) return;
+    if (node == NULL) {
+        return;
+    }
 
     if (node->type == NODE_BINARY_OP) {
         print_node(node->data.binary.right, depth + 1);