Working to create my own major mode for sqf language (arma3 scripting) I get this error:

Error during redisplay: (jit-lock-function 1) signaled (invalid-regexp "Regular expression too big")
Error during redisplay: (jit-lock-function 501) signaled (invalid-regexp "Regular expression too big")

The issue is a list of specific built-in language commands that reaches about 2500 of them initialized as following:

(defvar arma-commands
    "worldToScreen" ;; thats the 2500th command ;-)

Using the common (,(regexp-opt arma-commands 'words) . font-lock-builtin-face) for highlighting properly raises that error I mentioned before.

Is there any right and efficient way to solve this?

  • 3
    You could split it into multiple font-lock rules, where each rule would handle, say, 2000 entries. Having said this, is this really a god way to highlight a language? Maybe you could find highlighting rules which doesn't require a fixed list of reserved words. Jul 13, 2022 at 16:54
  • To add to my earlier response at emacs.stackexchange.com/a/72596/31220 .... Assuming 2500 words, back of napkin calculation shows that, the avg. size of each word has to be 26 = (/ (expt 2 16) 2500) for the jit lock to explode every time. What is the total length of all the words in your regexp?
    – user31220
    Jul 15, 2022 at 3:45
  • 2503 words as you can see it at this site: community.bistudio.com/wiki/Category:Arma_3:_Scripting_Commands. Actually @Lindydancer has the right answer: splitting all the scripting commands in groups although it also possible matching just a part of it (prefix) and not the enterely word (lot of commands share the same prefix).
    – xbelanch
    Jul 15, 2022 at 7:34

1 Answer 1


REG_ESIZE, /* Compiled pattern bigger than 2^16 bytes. */

According to https://git.savannah.gnu.org/cgit/emacs.git/tree/src/regex-emacs.c?h=53c0690fa28f338071703f1567d2d1c4054416f0#n1231

/* This is not an arbitrary limit: the arguments which represent offsets
   into the pattern are two bytes long.  So if 2^15 bytes turns out to
   be too small, many things would have to change.  */

# define MAX_BUF_SIZE (1 << 15)

So, I believe you are out of luck in configuring the limit.

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