pgsql: In pg_log_generic(), be more paranoid about preserving errno.

In pg_log_generic(), be more paranoid about preserving errno.

This code failed to account for the possibility that malloc() would
change errno, resulting in wrong output for %m, not to mention the
possibility of message truncation. Such a change is obviously
expected when malloc fails, but there's reason to fear that on some
platforms even a successful malloc call can modify errno.

Discussion: /messages/by-id/2576.1527382833@sss.pgh.pa.us

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/cf665ad4c89eb9b20285dc04aec906d46ed810d2

Modified Files
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src/common/logging.c | 2 ++
1 file changed, 2 insertions(+)