IV73852: BAD FILE DESCRIPTOR DUE TO OFSTREAM NOT RELEASING FILE AFTER ENOSPC

XL C/C++ for AIX Fix Pack 13 (August 2015 Update) for 12.1
XL C/C++ for AIX Fix Pack 22 (September 2015 PTF) for 11.1
XL C/C++ for AIX Fix Pack 21 (October 2015 PTF) for 10.1
XL C/C++ for AIX Fix Pack 14 (December 2015 Update) for 12.1
XL C/C++ for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 15 (April 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 16 (July 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 24 (September 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 17 (November 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C/C++ for AIX Fix Pack 21 (January 2019 Update) for 12.1

APAR status

• Closed as program error.

Error description

• An invalid FILE descriptor is kept by an ofstream object after
  encountering an ENOSPC 'No space left on device' error.
  
  The issue occurs when the ofstream close() function is called
  when the file system being written to is full.  The system
  fclose() function is called, which in turn calls fflush() to
  write out any remaining data.  The fflush() fails with an ENOSPC
  error due to the full filesystem, and fclose() returns -1.  Even
  though -1 is returned, the fclose() function releases the FILE
  descriptor.
  
  Because -1 is returned from fclose(), the ofstream close() sets
  the ofstream failbit to 1, however is_open is still 1, and the
  FILE descriptor associated with the ofstream object is still
  treated as active.
  
  If the ofstream object is used again, it will be acting upon an
  inactive, invalid FILE descriptor, and undefined behaviour may
  be seen.
  

Local fix

Problem summary

• PROBLEM DESCRIPTION:
  The ofstream object incorrectly keeps the file descriptor alive
  after fclose() failed and the is_open flag remains true. This
  allows the second fclose() to close the file but the file
  descriptor has been freed by the first fclose() and reused by
  the system for another file.  As a result, the second fclose()
  closes a different stream.
  
  USERS AFFECTED:
  Users who close a file stream twice because the first attempt
  failed with an error such as no space left on device.
  

Problem conclusion

• The ofstream object behavior does not comply with the C++
  standard and has now been fixed.
  
  This APAR (IV73852) denotes the fix to the <fstream> header
  file, which corrects the problem in applications that use
  ofstream directly in their code.  APAR IV78285 denotes a
  re-build of the XL C++ Runtime to use the fixed <fstream> header
  file, to ensure all usage of ofstream within the XL C++ Runtime
  itself is corrected.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  IV74072 IV74663

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels