Avoid somewhat-theoretical overflow risks in RecordIsValid().
This improves on commit 51fed14d73ed3acd2282b531fb1396877e44e86a by
eliminating the assumption that we can form <some pointer value> +
<some offset> without overflow. The entire point of those tests is that
we don't trust the offset value, so coding them in a way that could wrap
around if the buffer happens to be near the top of memory doesn't seem
sound. Instead, track the remaining space as a size_t variable and
compare offsets against that.
Also, improve comment about why we need the extra early check on
xl_tot_len.
Branch
------
master
Details
-------
http://git.postgresql.org/pg/commitdiff/10685ec082181b285a48d982b4c3463fd80ee5ae
Modified Files
--------------
src/backend/access/transam/xlog.c | 26 +++++++++++++++++---------
1 files changed, 17 insertions(+), 9 deletions(-)