[Ipopt] Missing random generator function using Cygwin 64

[Tony Kelman]

I know where it’s coming from, and it would also go away by upgrading autotools since this char *p = (char *) rand; method isn’t used in autoconf for checking the existence of a function any more. The mystery is why something that was a warning in GCC 4.8.2 (and everywhere else, except I think clang on Linux) would become an error in GCC 4.8.3 without changing any compiler flags. And whether that’s a Cygwin-only quirk, or would happen elsewhere. If it happens elsewhere, then it’s more of an issue and should maybe be reported to GCC as a regression since we’re not the only project in the world still using old autotools.

-Tony


From: Ted Ralphs 
Sent: Thursday, July 03, 2014 8:49 PM
To: Stefan Vigerske 
Cc: Tony Kelman ; ipopt 
Subject: Re: [Ipopt] Missing random generator function using Cygwin 64

I've replicated this on the Windows box I have on Jenkins. You can get all the build logs etc from there: 

http://jenkins.coin-or.org:8080/job/all-t-dll-x86_64-pc-cygwin-gcc4.8.1/135/console


Upgrading to 4.9.0 should fix the problem, as Stefan indicated, but I'll leave it on 4.8.3 to try to chase down the problem. Incidentally, I upgraded to 4.8.3 to try to fix what seemed to be a bug in 4.8.1 that was preventing OS from building.


Cheers,

Ted

Cheers,

Ted



On Tue, Jun 10, 2014 at 2:17 PM, Stefan Vigerske <stefan at math.hu-berlin.de> wrote:

  Hi,

  I'm running GCC 4.9.0 under Linux and get no problem:

  checking whether drand48 is declared... yes
  checking whether rand is declared... yes
  checking whether srand is declared... yes

  Stefan 


  On 06/10/2014 05:57 PM, Tony Kelman wrote:

    Good.

    This worries me slightly. If anyone on the mailing list has access to a Linux distribution where GCC 4.8.3 is already easily available, I’d appreciate if you could contact me and let me know whether or not you see the same thing. I have no idea at the moment whether this change in behavior is specific to Cygwin or will start showing up on Linux as well.

    Thanks,
    Tony


    From: Yao Xie
    Sent: Tuesday, June 10, 2014 8:28 AM
    To: Tony Kelman ; ipopt at list.coin-or.org
    Subject: RE: [Ipopt] Missing random generator function using Cygwin 64

    Yes, it works... after I downgraded gcc from 4.8.3 to 4.8.2

    Thanks again.

    Yao


    -------------------------------------------------------------------------------- 

    From: Tony Kelman (kelman at berkeley.edu)
    Sent: Tuesday, June 10, 2014 08:49 AM
    To: Yao Xie (xieyao04 at gmail.com); ipopt at list.coin-or.org
    Subject: Re: [Ipopt] Missing random generator function using Cygwin 64
    Ah, crap.
    conftest.cc:75:22: error: ISO C++ forbids casting between pointer-to-function and pointer-to-object [-Werror=pedantic]
        char *p = (char *) rand;
                           ^
    Apparently you’ve updated your GCC more recently than I have, and now in 4.8.3 this old-autotools method of checking for the existence of a function is an error, where it used to be a warning. I’m really surprised the grouping of a warning would be changed in a point release like that... the right solution is to update our autotools version, but that’s a big job that we haven’t put enough full-time work into yet. I’ll try to think if there’s a quick short-term fix for this, but in the meantime can you try reverting your GCC version to the previous release through Cygwin’s setup program?
    -Tony
    P.S: The attachment came through to me personally, but I guess not the mailing list. For future use you can try uploading log files somewhere like gist.github.com and send a link in your message.




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-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted
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