The perl script introduced by 86b008ee61 (t: add library for munging
chunk-format files, 2023-10-09) uses pack("Q") and unpack("Q") to read
and write 64-bit values ("quadwords" in perl parlance) from the on-disk
chunk files. However, some builds of perl may not support 64-bit
integers at all, and throw an exception here. While some 32-bit
platforms may still support 64-bit integers in perl (such as our linux32
CI environment), others reportedly don't (the NonStop 32-bit builds).
We can work around this by treating the 64-bit values as two 32-bit
values. We can't ever combine them into a single 64-bit value, but in
practice this is OK. These are representing file offsets, and our files
are much smaller than 4GB. So the upper half of the 64-bit value will
always be 0.
We can just introduce a few helper functions which perform the
translation and double-check our assumptions.
Reported-by: Randall S. Becker <randall.becker@nexbridge.ca>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When testing corruption of files using the chunk format (like
commit-graphs and midx files), it's helpful to be able to modify bytes
in specific chunks. This requires being able both to read the
table-of-contents (to find the chunk to modify) but also to adjust it
(to account for size changes in the offsets of subsequent chunks).
We have some tests already which corrupt chunk files, but they have some
downsides:
1. They are very brittle, as they manually compute the expected size
of a particular instance of the file (e.g., see the definitions
starting with NUM_OBJECTS in t5319).
2. Because they rely on manual offsets and don't read the
table-of-contents, they're limited to overwriting bytes. But there
are many interesting corruptions that involve changing the sizes of
chunks (especially smaller-than-expected ones).
This patch adds a perl script which makes such corruptions easy. We'll
use it in subsequent patches.
Note that we could get by with just a big "perl -e" inside the helper
function. I chose to put it in a separate script for two reasons. One,
so we don't have to worry about the extra layer of shell quoting. And
two, the script is kind of big, and running the tests with "-x" would
repeatedly dump it into the log output.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
