13 Dec
2017
13 Dec
'17
9:39 p.m.
Hi,
years ago I fixed some overflow bugs in v6. The file ctime.README
reads:
This tape (see enb.README) fixes some y2k and integer overflow issues
in V6.
ctime.c: Use Central European Timezone
ctime():
Don't blindly assume "19" to be the first two digits of the year.
gmtime():
The division of the current time by 8 hours overflows nowadays.
Instead divide by
24 hours, and use a routine which computes the quotient and remainder
with unsigned double word arithmetic. (ludiv())
If you want to understand ludiv and know modern program notations
have a look at ludiv.README.
date.c: Interpret the user entered year "00" as "2000", not as
"1900”.
The fixes are distributed on v6-tar tapes enblocked for simh (*.enb)
I think, the enb-directory is archived at tuhs. If not, let me know.
Here is the enb.README:
The contents of this directory are .README and .enb files with the
following basenames:
ctime: Some y2k related changes to V6.
dcheck: Bug fix and enhancement of dcheck.
dist: The V6 distribution tape: dist.README explains how to install
and setup V6 in the Supnik simulator. The file dist.enb is missing
for copyright and space reasons, you have to prepare it yourself.
(see enb.README).
dotdot: Kernel enhancement: If in a root directoy of a mounted filesystem,
let ".." mean the parent of the mount point, not the root directory.
enb: Conventions and usage of .enb files. Contains C-source of a program
which prepares tape files for the Supnik simulator and tells you
how to get the V6 distribution tape.
ludiv: Derivation of a double word unsigned division algorithm, which is used
in ctime. (no corresponding .enb)
man: The man command, which was missing from the distribution, and some
changes do make nroff output readable on an xterm.
Have fun,
Wolfgang Helbig
Stauferstr. 22
71334 Waiblingen