Libcperciva import #382
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Libcperciva import #382
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We tried to support valgrind checking of fork() in:
2023-09-20 tests/valgrind: improve handling for fork() and exec()
38e07b49d7bc662fb19917f07d19176d22cf9b54
However, that method assumed that the lowest pid would be the parent,
while the higher one(s) would be the children. That has two flaws:
1) If the pid rolls over, the order would be broken. For example, if
the parent pid was 99999 on FreeBSD (the maximum value), then the
child would be something much lower (probably in the hundreds).
(I knew about that problem, considered it sufficiently unlikely.)
2) Since $_valgrind_check_logfiles are defined by `ls "blah"*`, they are
listed in lexicographical order, not numerical order. For example,
given two logfiles foo-9999.log and foo-10000.log, foo-10000.log
would come first.
(I did not anticipate this problem, but even if it had occurred to
me, I probably would have deemed it sufficiently unlikely. However,
by unlikely fluke, this seems to occur roughly 50% of the time with
github actions: when checking 24-fork-func with the gcc binaries, the
parent lands on pid 9999 exactly and the child is 10000.)
The fix is not to rely on the order: instead, generate a list of all
pids involved. If a valgrind logfile lists a parent pid which is in
that list, it's a child; otherwise, it's the parent.
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