Comment #6 on issue 255 by [email protected]: Forking threads fails
with clang 3.4
http://code.google.com/p/address-sanitizer/issues/detail?id=255
A comment from dvyukov@ that didn't make it into the bug tracker:
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I'll find a workaround of my own, but I really think this is a regression
from ASan since it worked perfectly from day 1 and only broke when using
clang 3.4.
Yes, strictly saying it is legal.
POSIX says:
"A process shall be created with a single thread. If a multi-threaded
process calls fork(), the new process shall contain a replica of the
calling thread and its entire address space, possibly including the
states of mutexes and other resources. Consequently, to avoid errors,
the child process may only execute async-signal-safe operations until
such time as one of the exec functions is called. [THR] Fork
handlers may be established by means of thepthread_atfork() function
in order to maintain application invariants across fork() calls."
http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html
It's not even required to execute only async-signal safe functions. If
you are careful to establish invariants, you can use any functions.
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I'm afraid we'll finally need to intercept fork() (instead of using
pthread_atfork()) and at least clean up the thread registry in
sanitizer_common, because other tools may need it.
As we've seen recently, even in the case fork() is followed by exec()
(which is totally legitimate) we should be really careful to avoid
deadlocks in the tools' guts.
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