HowTo debugging

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Revision as of 10:47, 17 April 2009 by Mattijs (Talk | contribs)

If your application crashes it will usually output a stack trace, e.g.

  1. 0 Foam::error::printStack(Foam::-Ostream&) in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/"
  2. 1 Foam::sigFpe::sigFpeHandler(int) in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/"
  3. 2 Uninterpreted: [0xb7f8b420]
  4. 3 Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/"
  5. 4 void Foam::divide<foam::fvpatchfield,>(Foam::GeometricField<double,>&, Foam::GeometricField<double,> const&, Foam::GeometricField<double,> const&) in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libincompressibleTurbulenc"
  6. 5 Foam::tmp<foam::geometricfield<double,> > Foam::operator/<foam::fvpatchfield,>(Foam::tmp<foam::geometricfield<double,> > const&, Foam::GeometricField<double,> const&) in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libincompressibleTurbulenc"
  7. 6 Foam::turbulenceModels::kEpsilon::correct() in "/home/ivan/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libincompressibleTurbulenc"

There is lots of interesting information in there. It shows the type of error (sigFpe which means a division by zero or any other operation causing an invalid floating point number) and who causes it (operator/ of an fvPatchField). Further down the line is the originator, kEpsilon::correct() which obviously does some divisions. A good guess is that one of the patch fields of k or epsilon is 0.

From experience sigfpe originate from three sources:

  • as above - division by 0 from having an initial field set to 0.
  • when using floatTransfer = 1. This will truncate doubles into floats before doing parallel transfer so if the double does not fit it will produce a sigfpe. Check the traceback for a call to 'compressedSend'.
  • when using FOAM_SETNAN (initialises allocated memory to NaN) and accessing uninitialised memory.

The other common error is a segmentation violation (sigSegv) which is caused by an application accessing memory outside the allocated space. This are nearly always caused by a programming error.

If you want to find out more but not create a complete debugging build.

  • Find out from the printed stack trace which files contain the functions that crash. Copy these into your local directory.
  • Add the files to your Make/files
  • in Make/options: add


to EXE_INC and recompile. The 'FULLDEBUG' causes amongst others full range checking on Lists.