> < ^ Date: Fri, 19 May 2000 15:15:28 +0100
> < ^ From: Willem de Graaf <degraaf@math.uu.nl >
^ Subject: fix 3 for GAP4.2

Dear Forum,

This is to announce bugfix number 3 for GAP 4.2. The priority of this fix
is high.

Errors 6) and 12) also occur in GAP3 (see below). For GAP3 we have a
separate fix, which will be announced shortly.

You should not apply this fix to any version of GAP3, nor to any
version of GAP4.1.

This fix corrects:
1) A problem with GF(2) vectors on 64 bit systems.
2) A problem with the finitely presented group with 0 generators.
3) problems related to configuration, compilation, the GAP compiler, Exec
and so forth, on certain specific non-Linux systems, especially Irix.
4) A problem with `ConnectGroupAndCharacterTable'.
5) A problem with methods for `\<' for associative words.
6) A problem with `PresentationViaCosetTable'.
7) A problem with the function `ConjugateSubgroup'.
8) Problems related to finite field vectors and garbage collection.
9) A problem with `OneOfPcgs'.
10) A problem with `EpimorphismNilpotentQuotient'.
11) A problem with `AsGroupGeneralMappingByImages' (information that
was known from the input was not carried over to the output).
12) A problem with the functions `ImfInvariants' and `DisplayImfInvariants'.

Error 1) may cause GAP to enter an infinite loop.
Errors 2), 4), 7), 9) may cause GAP to signal an error.
Errors 5), 10) may produce wrong results.
Error 6) may cause wrong results (without evidence), or unexpected error
messages, or a segmentation fault.
Error 8) may cause GAP to enter a break loop, or even to produce
a segmentation fault.
Error 12) produces a wrong list of elementary divisors for the representative
group of the 7th Q-class of the irreducible maximal finite integral matrix
groups of dimension 20.

Many thanks to:
Burkhard H"ofling for reporting errors 1) and 9).
Franz Gaehler for reporting error 2).
Jeremy Rickard for reporting error 4).
Isabel Araujo for reporting error 5).
Isabel Araujo and Peter Campbell for reporting error 6).
Laurent Bartholdi for reporting error 7).
Juergen Mueller and Frank Luebeck for reporting eror 8).
Alex Turull for reporting error 11).
Burkhard H"ofling for the Macintosh binaries.

We also would like to thank the people who helped with the laborious process
of refining and testing the fix for problem 3).

Installing the bugfix.

Load the zoo archive `fix4r2n3.zoo' from the bugfixes web page
Alternatively you can find this file in the `bugfixes' directory of the
GAP4 ftp distribution.

Unpack the file in the home directory of your GAP distribution (the
directory containing the `lib' and `grp' directories) using `unzoo -x
fix4r2n3.zoo'. `unzoo' may ask you for permissions to overwrite files,
answer this with Y)es or A)ll. This will replace the erroneous files by
fixed versions.

(On a PC or a Mac you will have to copy `unzoo' in the same directory and
enter the argument line after the call to `unzoo'.)
Make sure you have write permissions when applying the fix.

This fix changes the kernel. You have to recompile by calling `make' in the
directory in which you unpacked the fix.

Windows users can find a new binary in the file `wbin4r2n3.zoo' in the
`bugfixes' directory: Extract this archive in the same place as the fix
archive to get a new `gapw95.exe' file.

Macintosh users should download the file 'bin4r2n3-PPC.sit' (for PPC
machines) or 'bin4r2n3-68k.sit' (for 68k machines), from the 'bugfixes'

If you get one of these precompiled binaries you do not need to get any
precompiled binaries that would have come with earlier fixes (these old
binaries are obsolete now). Similarly, if you cannot find these binaries but
have further, newer, fixes to install check whether new binaries with these
fixes did not make the binaries of this fix obsolete.

You can remove the file `description3' afterwards.

After installing the bugfix you can test whether
the bugfix has been applied correctly by starting GAP from the `gap4r2'
directory and issuing

gap> ReadTest("tst/bugfix.tst");
+ bugfixes test
+ GAP4stones: 835

(The output should be like this if the bugfixes have been installed
correctly. The number of GAP4stones may vary according to your system.)

Willem de Graaf, 19-May-00

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