[Lzip-bug] bug report: 'plzip -vf9' fails to compress files over a certain size

[Erik Jan Tromp]

I believe I've found a bug in plzip. Apologies for rambling.

software:
Slackware 14.2 (32 bit)
gcc (GCC) 5.3.0
plzip 1.6

hardware:
Intel(R) Core(TM) i7 CPU 930 @ 2.80GHz
quad core with hyperthreading
6GB RAM (not a typo)

fileset:
slackware-current sources. all '*.tar.*' decompressed to '*.tar'

test:
Compress each tarball with 'plzip -vf9 foo.tar'

Tarballs 421969920 bytes & larger: fail to compress
Tarballs 305926656 bytes & smaller: compress successfully

Out of 1591 tarballs tested, 10 reported errors as:
  foo.tar: Not enough memory. Try a smaller dictionary size
plzip: Deleting output file 'foo.tar.lz', if it exists.

A single time the error was reported as:
  foo.tar: Not enough memory. Try a smaller dictionary size
plzip: Deleting output file 'foo.tar.lz', if it exists.
plzip: Write error: Bad file descriptor

Successive attempts with 'plzip -vf9 -n8 foo.tar' through to 'plzip
-vf9 -n3 foo.tar' eventually compressed the outliers.

Tests were also performed on the following hardware using 'plzip -vf9
foo.tar' with no errors.

Intel(R) Atom(TM) CPU N270 @ 1.60GHz
single core with hyperthreading
1.5GB RAM

Intel(R) Atom(TM) CPU D525 @ 1.80GHz
dual core with hyperthreading
2GB RAM

Intel(R) Celeron(R) 3205U @ 1.50GHz
dual core without hyperthreading
8GB RAM

Intel(R) Core(TM) i3 CPU 530 @ 2.93GHz
dual core with hyperthreading
8GB RAM

Please note that while specifying '-n' & '-s' options are functional 
solutions, they are unacceptable for the intended use case. Regardless
of a machine's hardware, the resulting compressed files must be 
identical/predictable.

Erik

-- 
Talent hits a target no one else can hit; Genius hits a target no one
else can see.
 -- Arthur Schopenhauer