Subject: 24.3.91; "Arithmetic Error" in hide-ifdef mode when using shift operators
From: David Engster <[email-masked]>
To: [email-masked]
Date: Tue, 03 Jun 2014 21:12:33 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Recipe:

- Create a file "test.h" containing the following (this is from
  the file 'jiffies.h' in the Linux kernel):

#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
#endif

- emacs -Q

- Load the file, activate hide-ifdef-mode

- C-c @ h  (hide-ifdefs)

The minibuffer will show "Arithmetic Error". Here is the backtrace:

Debugger entered--Lisp error: (arith-error)
  hif-divide(0 nil)
  (hif-shiftleft (hif-divide (hif-shiftleft (hif-lookup (quote NSEC_PER_SEC)) 2) (hif-lookup (quote TICK_NSEC))) (hif-minus (hif-lookup (quote SEC_JIFFIE_SC)) 2))
  (hif-logand (hif-shiftleft (hif-divide (hif-shiftleft (hif-lookup (quote NSEC_PER_SEC)) 2) (hif-lookup (quote TICK_NSEC))) (hif-minus (hif-lookup (quote SEC_JIFFIE_SC)) 2)) 2147483648.0)
  (hif-not (hif-logand (hif-shiftleft (hif-divide (hif-shiftleft (hif-lookup (quote NSEC_PER_SEC)) 2) (hif-lookup (quote TICK_NSEC))) (hif-minus (hif-lookup (quote SEC_JIFFIE_SC)) 2)) 2147483648.0))
  eval((hif-not (hif-logand (hif-shiftleft (hif-divide (hif-shiftleft (hif-lookup (quote NSEC_PER_SEC)) 2) (hif-lookup (quote TICK_NSEC))) (hif-minus (hif-lookup (quote SEC_JIFFIE_SC)) 2)) 2147483648.0)))
  hif-possibly-hide()
  hide-ifdef-guts()
  hide-ifdefs()

Earlier Emacsen did not throw an error here (although it is very
possible that the above line wasn't calculated correctly). Still, this
probably qualifies as a regression.

-David