| commit | f39ad38410da554af54966bf74fa0402355852ac | [log] [tgz] |
|---|---|---|
| author | Jeff King <peff@peff.net> | Thu Jun 25 15:48:37 2020 -0400 |
| committer | Junio C Hamano <gitster@pobox.com> | Thu Jun 25 14:19:23 2020 -0700 |
| tree | 77a7d07f1287021f060f250cfdff7d4baadf30f3 | |
| parent | 8a494955835e3635926d4f6f4607c1ed95b011fc [diff] |
fast-export: use local array to store anonymized oid
Some older versions of gcc complain about this line:
builtin/fast-export.c:412:2: error: dereferencing type-punned pointer
will break strict-aliasing rules [-Werror=strict-aliasing]
put_be32(oid.hash + hashsz - 4, counter++);
^
This seems to be a false positive, as there's no type-punning at all
here. oid.hash is an array of unsigned char; when we pass it to a
function it decays to a pointer to unsigned char. We do take a void
pointer in put_be32(), but it's immediately aliased with another pointer
to unsigned char (and clearly the compiler is looking inside the inlined
put_be32(), since the warning doesn't happen with -O0).
This happens on gcc 4.8 and 4.9, but not later versions (I tested gcc 6,
7, 8, and 9).
We can work around it by using a local array instead of an object_id
struct. This is a little more intimate with the details of object_id,
but for whatever reason doesn't seem to trigger the compiler warning.
We can revert this patch once we decide that those gcc versions are too
old to care about for a warning like this (gcc 4.8 is the default
compiler for Ubuntu Trusty, which is out-of-support but not fully
end-of-life'd until April 2022).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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