[fitsbits] Important notice to CFITSIO users

[William Pence]

Important notice to users of the CFITSIO library.
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It has recently been discovered that in some limited cases CFITSIO may 
incorrectly read FITS data files when the CFITSIO library is compiled 
using v15.0 or v16.0 of the Intel C++ compilers.  This problem appears 
to be the result by a particular loop optimization technique used by 
these compilers (at the -O2 or -O3 optimization level) that causes a 
critical 'for' loop in CFITSIO to not be executed in strict sequential 
order.  This has the side effect of corrupting some of the data values 
that are being read from the FITS file.  Note that this 'for' loop is 
only used when reading 32-bit integer values from a FITS image with 
BITPIX = 32 or from a FITS binary table column with TFORMn = 'J'.  
Reading other data types is unaffected, as is the writing of all types 
of data.

At this time, only the Intel compilers are known to cause this problem, 
and most other commonly used C or C++ compilers produce correct code.  
One can determine whether the CFITSIO library on a particular system is 
affected by this problem by comparing the output of the testprog.c 
program that is distributed with CFITSIO with the testprog.out text 
file.  If there are no differences, then CFITSIO is working correctly.

A new 3.38 version of CFITSIO is now available at

http://heasarc.gsfc.nasa.gov/docs/software/fitsio/fitsio.html

which fixes the underlying cause of this problem.  It is highly 
recommended that all users of any previous version of CFITSIO upgrade to 
this new version at their earliest convenience. Besides fixing this 
problem when using the Intel compiler, it also safeguards users in the 
event that new versions of other compilers adopt similar aggressive loop 
optimization techniques.

If you have any further questions or concerns please contact me or the 
HEASARC software support staff directly (and preferably not here on the 
fitsbits email list).

-Bill Pence