don't return uninitialized memory from bdiff.blocks() bdiff.blocks() returns a dummy match at the end of both files; the length of that chunk is never set, so it will sometimes contain random heap garbage. There are apparently workarounds for this elsewhere: # bdiff sometimes gives huge matches past eof, this check eats them,

#!/bin/sh

hg init

echo a > a
hg ci -d '0 0' -Ama

hg an a

echo "[ui]" >> $HGRCPATH
echo "strict=True" >> $HGRCPATH

hg an a
hg annotate a

echo % should succeed - up is an alias, not an abbreviation

hg up