I am using auto-complete-mode with ac-c-headers and whenever I type std:: There is a long (~30 seconds) pause, presumably while the candidates list is populated. This happens every time, which suggests that there is no caching to speed things up for the next time.

Is there a way to avoid the pause after every time I type std::?


Using the emacs profiler, I have now discovered that the pretty much all of the time is being spent in the functions semantic-analyze-possible-completions and semantic-analyze-current-context. This suggests that the real problem probably lies with semantic. I have also learned that including anything from the Boost libraries causes a significant increase in the amount of time required for semantic to return possible completions.

(In case it makes a difference, I am using Emacs 24.5 on Linux)

  • I don't use auto-complete-mode, but 30 seconds is really long! If you don't get an answer here, consider contacting the package maintainer -- 30 sec is long enough to suspect a bug. You might also try debugging it, with M-x debug-on-entry for the function that performs the completion.
    – Drew
    Oct 16 '15 at 5:51
  • You're not on Windows or Cygwin are you?
    – nanny
    Oct 21 '15 at 18:44
  • @nanny: no, this is on RHEL.
    – nispio
    Oct 21 '15 at 20:17
  • Are you satisfied with disabling semantic-mode and only leave auto-complete-mode on? Jan 15 '17 at 21:46
  • Same problem here. Have you solved the issue in the meanwhile ?
    – user52366
    May 23 '19 at 12:15

I've hit this same problem before and I "solved" it by changing the value of ac-delay from 0.1s to 1.0, like so:

(set-variable 'ac-delay 1.0)

That means that as I'm typing it only attempts the auto-complete if I stop typing for a second. So if you know you want a std::vector you can just keep typing and auto-complete never fires.

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