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avoid mktemp/mkstemp internally


From: Mike Frysinger
Subject: avoid mktemp/mkstemp internally
Date: Fri, 13 May 2016 14:40:07 -0400

i was pointed at a bug report for FreeBSD systems [1] where running lots
of processes in parallel would randomly fail with errors like:
  cannot make pipe for process substitution: File exists

upstream FreeBSD addressed this by defining USE_MKTEMP [2] & USE_MKSTEMP
[3] when building bash.  looking at the source in bash though, i can't
see why these aren't always defined.  why does bash try to reimplement
both funcs ad-hoc instead of just using the stable/guaranteed system
versions ?

the bash versions seem like it's pretty trivial to collide: it mixes
current seconds count, current pid number, and a counter.  when you
factor in modern tech like linux pid namespaces, it's trivial to get
a situation where the pid/time are the same values.
-mike

[1] https://bugs.gentoo.org/574426
[2] https://svnweb.freebsd.org/ports?view=revision&revision=391614
[3] https://svnweb.freebsd.org/ports?view=revision&revision=391692

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