From 4815c3c4b26a91301c51360297ebfdef3b96a4ce Mon Sep 17 00:00:00 2001 From: Jeff King Date: Fri, 3 Nov 2023 12:20:19 -0400 Subject: [PATCH] t: avoid perl's pack/unpack "Q" specifier 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 Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- t/lib-chunk/corrupt-chunk-file.pl | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/t/lib-chunk/corrupt-chunk-file.pl b/t/lib-chunk/corrupt-chunk-file.pl index cd6d386fef..0e11aadda8 100644 --- a/t/lib-chunk/corrupt-chunk-file.pl +++ b/t/lib-chunk/corrupt-chunk-file.pl @@ -21,6 +21,30 @@ sub copy { return $buf; } +# Some platforms' perl builds don't support 64-bit integers, and hence do not +# allow packing/unpacking quadwords with "Q". The chunk format uses 64-bit file +# offsets to support files of any size, but in practice our test suite will +# only use small files. So we can fake it by asking for two 32-bit values and +# discarding the first (most significant) one, which is equivalent as long as +# it's just zero. +sub unpack_quad { + my $bytes = shift; + my ($n1, $n2) = unpack("NN", $bytes); + die "quad value exceeds 32 bits" if $n1; + return $n2; +} +sub pack_quad { + my $n = shift; + my $ret = pack("NN", 0, $n); + # double check that our original $n did not exceed the 32-bit limit. + # This is presumably impossible on a 32-bit system (which would have + # truncated much earlier), but would still alert us on a 64-bit build + # of a new test that would fail on a 32-bit build (though we'd + # presumably see the die() from unpack_quad() in such a case). + die "quad round-trip failed" if unpack_quad($ret) != $n; + return $ret; +} + # read until we find table-of-contents entry for chunk; # note that we cheat a bit by assuming 4-byte alignment and # that no ToC entry will accidentally look like a header. @@ -28,7 +52,7 @@ sub copy { # If we don't find the entry, copy() will hit EOF and exit # (which should cause the caller to fail the test). while (copy(4) ne $chunk) { } -my $offset = unpack("Q>", copy(8)); +my $offset = unpack_quad(copy(8)); # In clear mode, our length will change. So figure out # the length by comparing to the offset of the next chunk, and @@ -38,11 +62,11 @@ sub copy { my $id; do { $id = copy(4); - my $next = unpack("Q>", get(8)); + my $next = unpack_quad(get(8)); if (!defined $len) { $len = $next - $offset; } - print pack("Q>", $next - $len + length($bytes)); + print pack_quad($next - $len + length($bytes)); } while (unpack("N", $id)); }