sources-request@mirror.UUCP (08/11/86)
Submitted by: cca!astrovax!wls (William L. Sebok)
Mod.sources: Volume 6, Issue 100
Archive-name: malloc.patch
My recent malloc posting [Volume 6, #54 --r$] has a bug in the realloc
routine. If the area of memory is to be expanded in size and if it
sits adjacent to the "break" then the area is expanded by moving the
break. Unfortunately, in this case I forgot to mark the area of memory
as Busy and take it off the Free queues. Horrible things may then
happen if a latter malloc grabs this memory hunk. Thanks to elsie!ado
for finding the bug.
Bill Sebok Princeton University, Astrophysics
{allegra,akgua,cbosgd,decvax,ihnp4,noao,philabs,princeton,vax135}!astrovax!wls
#!/bin/sh
# This is a shell archive. Remove anything before this line,
# then unpack it by saving it in a file and typing "sh file".
# Wrapped by mirror!rs on Mon Aug 11 16:07:13 EDT 1986
# Contents: malloc.patch
echo x - malloc.patch
if test -f malloc.patch ; then
echo malloc.patch exists, putting output in $$malloc.patch
OUT=$$malloc.patch
else
OUT=malloc.patch
fi
sed 's/^XX//' > $OUT <<'@//E*O*F malloc.patch//'
XX*** /tmp/,RCSt1000667 Sat Aug 2 22:49:47 1986
XX--- realloc.c Thu Jul 31 17:01:57 1986
XX***************
XX*** 71,76
XX nbytes += sizeof(struct overhead);
XX BRK((char *)p + nbytes);
XX p->ov_length = nbytes;
XX return(mem);
XX }
XX
XX--- 71,79 -----
XX nbytes += sizeof(struct overhead);
XX BRK((char *)p + nbytes);
XX p->ov_length = nbytes;
XX+ /* declare it to be busy */
XX+ remque(TOBUK(p));
XX+ p->ov_magic = MAGIC_BUSY;
XX return(mem);
XX }
@//E*O*F malloc.patch//
chmod u=rw,g=rw,o=rw malloc.patch
echo Inspecting for damage in transit...
temp=/tmp/sharin$$; dtemp=/tmp/sharout$$
trap "rm -f $temp $dtemp; exit" 0 1 2 3 15
cat > $temp <<\!!!
20 60 450 malloc.patch
!!!
wc malloc.patch | sed 's=[^ ]*/==' | diff -b $temp - >$dtemp
if test -s $dtemp
then echo "Ouch [diff of wc output]:" ; cat $dtemp
else echo "No problems found."
fi
exit 0