[fitsbits] Clarification of EXTEND, please

[Thierry Forveille]

Stephen Walton writes:
 > Without naming names, I just today hit a conflict between two pieces of
 > software.  One created a FITS file with only a single HDU whose header
 > contained the line 'EXTEND = F'.  A second piece of software interpreted
 > the presence of the EXTEND keyword in the primary HDU as meaning it
 > should check for extensions, tried to fseek() beyond the end of the
 > primary HDU and data array, and died.
 > 
 > Who did what right and wrong in this scenario?  I'll send bug reports
 > with the correct answers to the software authors.
 > 
The second piece did wrong, twice :-) EXTEND indicates only that the file
may contain an extension, not that it does, and then only when set to T.
It looks like they took two unwarranted shortcuts...