[cfe-dev] [cxxabi] Thread-safe statics causing deadlocks

[Craig, Ben via cfe-dev]

On 7/21/2016 4:27 AM, David Chisnall wrote:
> I believe that the text of the standard is fine, however. The 
> implementation does not introduce deadlocks, the user code introduces 
> deadlocks.
The code snippets provided run without deadlocks if thread-safe statics 
are disabled.  There are also no user-level data races.  The standard 
seems pretty clear to me that this behavior isn't allowed.

I think that C++ code is better with the per-object locks in place, but 
the standard is unclear on what is considered allowable behavior.  I 
believe the standard permits a global lock, or a per-object lock, or 
something in between.  The implementation choice affects what is valid 
user code.  My "highly contrived" example wouldn't deadlock with a 
single global lock implementation, but the "lightly contrived" example will.

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