Date: Sat, 11 Sep 2010 16:05:45 +0200 From: "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de> To: Mehmet Erol Sanliturk <m.e.sanliturk@gmail.com> Cc: Andrew Brampton <brampton+freebsd@gmail.com>, freebsd-questions@freebsd.org Subject: Re: Compiling software with different compiler than cc or clang results in unusable output Message-ID: <4C8B8CB9.4010104@mail.zedat.fu-berlin.de> In-Reply-To: <AANLkTinmMDSP=Ci5GkogcD744zcy8uyP6gY7uuqLR8-_@mail.gmail.com> References: <4C8B4BC0.1000900@mail.zedat.fu-berlin.de> <AANLkTinymkQeeLhdbWYP=eEHEtViWVRscJ0-dVPJBX6u@mail.gmail.com> <AANLkTinmMDSP=Ci5GkogcD744zcy8uyP6gY7uuqLR8-_@mail.gmail.com>
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On 09/11/10 14:26, Mehmet Erol Sanliturk wrote: > > > On Sat, Sep 11, 2010 at 5:43 AM, Andrew Brampton > <brampton+freebsd@gmail.com <mailto:brampton%2Bfreebsd@gmail.com>> wrote: > > On 11 September 2010 10:28, O. Hartmann > <ohartman@mail.zedat.fu-berlin.de > <mailto:ohartman@mail.zedat.fu-berlin.de>> wrote: > > > > Dear Sirs, > > > > you see me a kind of desperate. I wrote my own a small piece of >  software in > > C, calculating the orbit and position of astronomical objects, > astroids, in > > a heliocentric coordinate system from Keplerian orbital elements. > So far. > > The software calculates the set of points of an ellipse based upon > > ephemeridal datas taken from the Minor Planet Cataloge. Again, so > far, > > everything all right. The set of points of an orbit is all right and > > correct. But when it comes to positions at a specific time, then > I loose > > hair! > > > > Compiling this piece of software with FreeBSD's gcc (V4.2) and > clang (clang > > devel) on my private and lab's FreeBSD boxes (both most recent > FreeBSD > > 8.1/amd64), this program does well, the calculated orbital > positions are > > very close to professional applications or observational checks. > But when > > compiling the sources with gcc44 or gcc45 (same source, same > CFLAG setting, > > mostly no CFLAGS set), then there is a great discrepancy. > Sometimes when > > plotting positions, the results plotted seconds before differs > from the most > > recent. The ellipses are allways correct, but the position of a > single point > > at a specific time isn't correct. > > > > I use the GNU autotools to build the package. > > > > I suspekt miscompilations in memory alloction or in some time- or > > mathematical functions like sin, cos. > > > > before I digg deeper I'd like to ask the community for some hints > how to > > hunt down such a problem. > > > > regards, > > Oliver > > Sounds a cool project. I suspect you are miss-using a feature of C or > are using uninitialised memory, and with gcc44/45's more aggressive > optimisations it is getting it wrong. I have three suggestions > > 1) Use valgrind to check if it finds anything wrong when running your > program. Check both the good and the bad builds. > > 2) If your program is made up of multiple C files, then try compiling > all of the C files with gcc42, but just one at a time with gcc44. This > way will help you track down exactly which C file has "the bug". > > 3) Finally do some printf debugging to find the first line of code > that is generating the wrong value. > > I hope these suggestions help. > Andrew > > > > Another check may be to use Sun Studio C and or Fortran compilers . > These can be used in Linux ( Linux version of Sun Studio ) and/or > OpenSolaris or Solaris ( Solaris version of SunStudio ( both in x86 , > x86_64 , Sparc ) ( all of them are ( Solaris , OpenSolaris , Sun > Studio , Linux  )  free ) . All of them are freely downloadable from > www.sun.com <http://www.sun.com>; and/or www.opensolaris.com > <http://www.opensolaris.com>; ( these sites or their pages may be > redirected to www.oracle.com <http://www.oracle.com>; owned pages ) . > > Personally I tried GCC compilers , but I found that they are very > unreliable . Now I am using Sun Studio compilers in OpenSolaris and > Linux , and never GCC compilers . > > Thank you very much . > > Mehmet Erol Sanliturk > > > >  Hello. Well, the only other architectures I have access to are Linux boxes. clang ist a very nice compiler since its syntax checking is formidable. But its code is slow and there seems no OpenMP support at the moment. Oliver
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