Hi Mark,
> I am having a problem writing netCDF "classic" files larger than 2GB
> when building with the Microsoft Visual Studio 2008 compiler. The same
> code works fine when build on Linux, and on Cygwin.
>
> A bit of background. This is a project to build generic file writers
> for cameras and detectors in the areaDetector package
> (http://cars9.uchicago.edu/software/epics/areaDetectorDoc.html) for the
> EPICS (http://www.aps.anl.gov/epics/) real-time control system. This is
> a large project, with its own build system based on gnumake. I am
> building the basic netCDF library from the same source code on all
> supported platforms (Linux 32 and 64-bit, Windows 32 and 64-bit with
> Microsoft compiler, Windows with Cygwin gcc compilet, vxWorks, Darwin,
> Solaris, etc.). Because I have another file writer that handles HDF5, I
> am using netCDF 3.6.3, since I only want to netCDF to create "classic"
> files. I am using 3.6.3 because it is less complex than 4.x, not
> requiring any HDF5 support, etc.
I recommend you use the latest netCDF-4 release, 4.1.3. If you don't
have and HDF5 library installed, it will be built without support for
netCDF-4, but with bug fixes since 3.6.3 was released 3 years ago. For
example, these bug fixes were mentioned in the RELEASE_NOTES for 4.1.2:
Fixed two large-file bugs with using classic format or
64-bit offset format and accessing multidimensional
variables with more than 2**32 values.
If the problem you're seeing still occurs in releases since 4.1.2, it
may be something new.
--Russ
> The application is typically streaming uncompressed images, using the
> UNLIMITED dimension as the streaming dimension. Thus, each record is
> small, only a few MB, and the file size limitations of the classic
> format are not a problem. Here is an ncdump of a file header created
> with this file writer on Linux:
>
> corvette:ADApp/op/adl>ncdump -h /home/epics/scratch/netcdf_test_1.nc
> netcdf netcdf_test_1 {
> dimensions:
> numArrays =3D UNLIMITED ; // (4100 currently)
> dim0 =3D 1024 ;
> dim1 =3D 1024 ;
> attrStringSize =3D 256 ;
> variables:
> int uniqueId(numArrays) ;
> double timeStamp(numArrays) ;
> byte array_data(numArrays, dim0, dim1) ;
> int Attr_ColorMode(numArrays) ;
> double Attr_AcquireTime(numArrays) ;
> double Attr_RingCurrent(numArrays) ;
> char Attr_RingCurrent_EGU(numArrays, attrStringSize) ;
> double Attr_ID_Energy(numArrays) ;
> char Attr_ID_Energy_EGU(numArrays, attrStringSize) ;
> int Attr_ImageCounter(numArrays) ;
> int Attr_MaxSizeX(numArrays) ;
> int Attr_MaxSizeY(numArrays) ;
> char Attr_CameraModel(numArrays, attrStringSize) ;
> char Attr_CameraManufacturer(numArrays, attrStringSize) ;
>
> // global attributes:
> :dataType =3D 1 ;
> :NDNetCDFFileVersion =3D 3. ;
> :numArrayDims =3D 2 ;
> :dimSize =3D 1024, 1024 ;
> ...
>
> So the only large array is called "array_data", and in this case it is
> [4100, 1024, 1024], where 4100 is the unlimited dimension. Thus, this
> file is over 4GB, and it can be written and read with no problems on
> Linux and Cygwin. It also works fine when writing files on Windows with
> the Microsoft compiler, up to file sizes of 2GB.
>
> However, when I try to write a file on Windows larger than 2GB using the
> program built with the Visual Studio compiler I get the following error:
>
> Assertion failed: pxp->bf_offset <=3D offset && offset < pxp->bf_offset =
> +
> (off_t) pxp->bf_extent, file ..\posixio.c, line 325
>
> When I look at the code at line 325 in posixio.c, I see that offset and
> pdxp->bf_offset are of type off_t. I added a printf() in that code to
> print the sizeof(offset) and sizeof(off_t), and it comes up as 4, not 8.
>
>
> But when I look at the config.h file that comes in the win32/NET
> directory in netCDF 3.6.3 it has the following:
> corvette:areaDetector/ADApp/netCDFSrc>grep -C3 off_t
> /usr/local/netcdf/netcdf-3.6.3/win32/NET/config.h
> /* #undef HAVE_ST_BLKSIZE */
>
> /* Define to `long' if <sys/types.h> doesn't define. */
> /* #undef off_t */
>
> /* Define to `unsigned' if <sys/types.h> doesn't define. */
> /* #undef size_t */
> --
> /* The number of bytes in a size_t */
> #define SIZEOF_SIZE_T 4
>
> /* The number of bytes in a off_t */
> #define SIZEOF_OFF_T 8
>
> /* Define to `int' if system doesn't define. */
>
>
> So it defines SIZEOF_OFF_T to be 8, not 4.
>
> I have generated the netCDF config.h file on Linux, but then edited it
> to correctly (?) define things on other platforms, like _WIN32 and
> vxWorks.
>
> The compiler flags being used on Windows are illustrated in the
> following output when I build:
>
> cl -c /nologo /D__STDC__=3D0 /D_CRT_SECURE_NO_DEPRECATE
> /D_CRT_NONSTDC_NO_DEPRECATE /Ox /GL /W3 /w44355
> /D_WIN32_WINNT=3D0x0503 -D_FILE_OFFSET_BITS=3D64 /MT -DEPICS_DLL_NO =
> -I.
> -I..\\O.Common -I. -I.. -I..\\..\\..\\include\\os\\WIN32
> -I..\\..\\..\\include -IJ:\\epics\\devel\\asyn-4-17\\include
> -IJ:\\epics\\devel\\calc-2-8\\include
> -IJ:\\epics\\devel\\busy-1-3\\include
> -IJ:\\epics\\devel\\sscan-2-6-6\\include
> -IJ:\\epics\\devel\\mca-6-12-4\\include
> -IJ:\\epics\\devel\\autosave-4-7\\include\\os\\WIN32
> -IJ:\\epics\\devel\\autosave-4-7\\include
> -IJ:\\epics\\devel\\areaDetector-1-7beta1\\include\\os\\WIN32
> -IJ:\\epics\\devel\\areaDetector-1-7beta1\\include
> -IH:\\epics\\base-3.14.12.1\\include\\os\\WIN32
> -IH:\\epics\\base-3.14.12.1\\include ..\\var.c
>
> There is something I don't understand here.
>
> Has netCDF 3.6.3 been tested to correctly write classic files > 2GB with
> the Microsoft compiler? Why am I getting the assert error?
>
> Thanks very much,
> Mark Rivers
