PM81270: INCORRECT # BYTES READ RETURNED ON 1ST FREAD, AFTER AN FGETPOS, FOR AN RECFM=U FILE.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• For an RECFM=U dataset, which is empty, the very first fread
  gets EOF from OSREAD and moreover '0' bytes read.
  
  But, if before the first fread, an fgetpos is done,
  the RECFM=U case returns the blksize value (8192 in this
  case) instead of 0 in that first fread.
  
    The rp84 read peg, never calls OSREAD the first time. It
  explicitly returns the blksize value due to a 'readdeferred'
  setting.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of RECFM=U data sets opened for        *
  *                 read and using Record I/O (type=record).     *
  ****************************************************************
  * PROBLEM DESCRIPTION: When the RECFM=U data set is empty,     *
  *                      an fread() correctly returns 0 bytes    *
  *                      read and feof() is true.  However, if   *
  *                      a call to fgetpos() is inserted         *
  *                      before the fread(), then fread()        *
  *                      incorrectly returns 'blksize' bytes,    *
  *                      as if a block had been read.            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  See problem description.
  

Problem conclusion

• The code that handles RECFM=U Record I/O is corrected to
  properly handle the case when the data set is empty and opened
  for read.  The first fread, whether or not preceded by a call to
  fgetpos, fseek (that does not change the position), or rewind
  will return 0 bytes.
  

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:

  UK91487 UK91489

Modules/Macros

• CELHP084 CELQP084 EDC40052
  

Fix information

• Fixed component name

  LE C LIBRARY

• Fixed component ID

  568819805

Applicable component levels

• R770 PSY UK91489

     UP13/02/27 P F302

• R780 PSY UK91487

     UP13/02/27 P F302

Fix is available

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