[asterisk-bugs] [JIRA] (ASTERISK-27619) Build System: Require compiler to provide built-in support for atomic references.

[Corey Farrell (JIRA)]

Corey Farrell created ASTERISK-27619:
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             Summary: Build System: Require compiler to provide built-in support for atomic references.
                 Key: ASTERISK-27619
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-27619
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Core/BuildSystem
    Affects Versions: GIT
            Reporter: Corey Farrell


I'm working with the jansson project to get thread safe reference counting \[1\].  I'm getting some push-back on the pieces necessary to emulate atomic operations.  I'm proposing that Asterisk 16+ should require the availability of __sync or __atomic built-ins:
* __sync_fetch_and_add or __atomic_fetch_add (used by AO2)
* __sync_add_and_fetch or __atomic_add_fetch (to be used by jansson)
* __sync_lock_test_and_set / __sync_lock_release or the __atomic equivalents (used by spinlock.h)

All of these __sync functions have been available since gcc-4.1.2 \[2\] (released in 2007).  The __atomic variants are newer and I believe they should be preferred if available.  This is in preparation for Asterisk 16+ hopefully requiring jansson 2.11+ and removing most (or all) locking from main/json.c.

\[1\]: https://github.com/akheron/jansson/pull/389
\[2\]: https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html



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