safely abort on exec of uninitialized mem or addr 0

include/fh_config.h

@@ -7,8 +7,8 @@
 #ifndef FORTH_FH_CONFIG_H
 #define FORTH_FH_CONFIG_H
 
-#define DATA_STACK_DEPTH 16
-#define RETURN_STACK_DEPTH 16
+#define DATA_STACK_DEPTH 256
+#define RETURN_STACK_DEPTH 256
 #define MAX_NAME_LEN 32
 #define HEAP_SIZE (1024*1024)
 #define MAXLINE 65535

include/fh_error.h

@@ -30,7 +30,7 @@ enum fh_error {
   FH_ERR_NOT_APPLICABLE,
   FH_ERR_PICTNUM_FULL,
   FH_ERR_BAD_DEFER,
-  FH_ERR_ABORT, // technical error used to abort from nested input source
+  FH_ERR_BAD_OPCODE,
   FH_ERR_MAX,
 };