Detect calls of thread-unsafe functions as races

[sim642]

Under "Thread-safe functions" of pthreads man page, it says the following:

A thread-safe function is one that can be safely (i.e., it will deliver the same results regardless of whether it is) called from multiple threads at the same time.
POSIX.1-2001 and POSIX.1-2008 require that all specified in the standard shall be thread-safe, except for following functions:

Then a list of possibly thread-unsafe functions follows.

We should consider calls to these functions (in place of global variables) and report racing calls (in place of accesses).

I was reminded of this when trying to figure out why chrony uses a global lock to protect what seems to be thread-local data manipulation. It doesn't call any functions from this list, but for completenes it would be nice to detect as well.

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The following thread-unsafe functions remain to be added to libraryFunctions.ml:

• ecvt()
• ftw()
• nftw()
• setkey()
• wcsrtombs()
• wcstombs()
• wctomb()

Originally posted by @karoliineh in #1079 (comment)

[sim642]

Related to a couple of *_unlocked functions from the list, turns out there are flockfile, ftrylockfile and funlockfile, which treat a FILE as a mutex. No idea, if anyone uses them, but I guess it wouldn't hurt to also consider those for mutual exclusion.

[michael-schwarz]

Related to a couple of *_unlocked functions from the list, turns out there are flockfile, ftrylockfile and funlockfile, which treat a FILE as a mutex. No idea, if anyone uses them, but I guess it wouldn't hurt to also consider those for mutual exclusion.

Should we move this to a new issue?