This is the mail archive of the
mailing list for the Cygwin project.
Re: mktime loop
- From: Denis Excoffier <cygwin at Denis-Excoffier dot org>
- To: cygwin at cygwin dot com
- Date: Thu, 16 May 2013 19:13:34 +0200
- Subject: Re: mktime loop
- References: <5244063b734b165baf34bdebaff0aca5 at denis-excoffier dot org> <20130513153651 dot GD5045 at calimero dot vinschen dot de> <20130513154921 dot GF8890 at calimero dot vinschen dot de> <27BBE8FE-303A-432D-94AA-AF834124D125 at Denis-Excoffier dot org> <20130513165712 dot GH8890 at calimero dot vinschen dot de> <20130514133950 dot GC23910 at calimero dot vinschen dot de>
On 2013-05-14 15:39, Corinna Vinschen wrote:
> On May 13 18:57, Corinna Vinschen wrote:
>> On May 13 18:41, Denis Excoffier wrote:
>>> On 2013-05-13 17:49, Corinna Vinschen wrote:
>>>> Erm... hang on. Is that really a problem? 2147483647 is 0x7fffffff,
>>>> which is the maximum you get with a 4 byte time_t (== signed long)
>>>> anyway. If you switch the date to 2038-01-20, the value will be
>>>> negative, and therefore outside the scope of the 4 byte time_t. So this
>>>> is a hard restriction of using 4 byte time_t.
>>>> The solution is:
>>>> - Either somebody changes 32 bit Cygwin to 8 byte time_t while keeping
>>>> all the 4 byte time_t APIs intact to maintain compatibility with
>>>> existing binaries(*),
>>>> - or, you switch to a 64 bit Windows and use 64 bit Cygwin ;)
>>> I understand.
>>> I suppose you will however be willing to provide us a means to workaround
>>> the "autoconf mktime usability test failing" (see for example in
>>> gawk-4.1.0 where all the tm fields are set to 128). Now, instead of only
>>> failing (i presume), it hangs. Sorry, this specific point should have been
>>> noticed in my original post.
>>> Or do we have to patch every impacted ./configure?
>> Good point. I guess the right thing to do here is for mktime to
>> return -1 instead of hanging. I look into that.
> Looks like this is a result of gcc optimization settings. The upstream
> code computing time_t <-> struct tm conversions requires integer
> overflow to be fully defined, but gcc's -O2 option sets
> -fstrict-overflow which results in all kinds of agressive integer
> optimizations which disabled utilizing integer overflows for serious
> purposes. I fixed that by setting the -fwrapv option when building the
> affected localtime.cc file (thanks to Kai Tietz for pointing this out).
I can confirm that the last snapshot (20130516) fixes the problem.
Problem reports: http://cygwin.com/problems.html
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple