Index: a/parser.y
===================================================================
--- a/parser.y
+++ a/parser.y
@@ -16,8 +16,9 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 #include <math.h>
 #include <stdint.h>
+#include <stdlib.h>
 #define YYSTYPE	int32_t
 extern int32_t end_result;
 extern int yylex(void);
 extern int yyerror(const char *);