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bug#17681: 24.3.91; "Arithmetic Error" in hide-ifdef mode when using shi
From: |
Glenn Morris |
Subject: |
bug#17681: 24.3.91; "Arithmetic Error" in hide-ifdef mode when using shift operators |
Date: |
Thu, 05 Jun 2014 18:26:15 -0400 |
User-agent: |
Gnus (www.gnus.org), GNU Emacs (www.gnu.org/software/emacs/) |
Luke, could you take a look at this report please?
http://debbugs.gnu.org/17681
An artificial but smaller example might be:
#if 1 / FOO
#endif
David Engster wrote:
> 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.