[IGSMAIL-5615]: A harmful bug in CRX2RNX was found and fixed

[Yuki Hatanaka]

******************************************************************************
IGS Electronic Mail      22 Jun 03:14:29 PDT 2007      Message Number 5615
******************************************************************************

Author: Yuki Hatanaka

Dear colleagues,

A harmful bug was found in the RINEX uncompression program 
CRX2RNX. The bug resides only in the crx2rnx.c versions 
4.0.0-4.0.2. Since rnx2crx.c is free from this bug, the 
Compact RINEX files just compressed with RNX2CRX of 
these versions are not affected (unless re-compressed
after uncompression).
I'm sorry for the trouble the bug may cause.

All the package files in the GSI's FTP server was replaced 
with bug fixed ones with updating the version of software 
from 4.0.2 to 4.0.3:
ftp://terras.gsi.go.jp/software/RNXCMP_4.0.3/

The followings are the detailes about the bug.
Reported problem:
  CRX2RNX version 4.0.2 produced corrupted RINEX files 
  when being applied to some of Compact RINEX files of 
  1 Hz sampling, although an old version (2.4.3) of 
  CRX2RNX uncompressed the same file correctly.
The cause:
  In process of uncompress of a data arc, value of some
  specific intermediate variables may drift in a 
  randome-walk-like manner and may overflow eventually 
  and corrupt the recovered output of RINEX files. 
  The drift was caused by omission of carrying numbers 
  in a intermediate process. The higher the sampling rate
  is, the more likely an overflow may take place, hence. 
Solution:
  Drift and overflow of the intermediate variable was 
  prevented by adding process of carrying numbers.
  new version 4.0.3 is created.

Finally, I would thank Mark Schenewerk for reporting 
the problem and providing a sample file, which was 
helpful to identify the cause of the bug.

Best Regards,

Yuki

----------------------------------------------------
Yuki Hatanaka, Ph.D, Geographical Survey Institute
e-mail : hata at gsi.go.jp
---------------------------------------------------