- Evaluate the memory order argument in atomic_fetch_*_explicit macros.
- Implement atomic_store_explicit using atomic_exchange_explicit instead
of a plain assignment.
Reviewed by: theraven
MFC after: 2 weeks
- Replace do-while statements with void expressions.
- Wrap __asm statements in statement expressions.
- Make the macros function-like:
- Evaluate all arguments exactly once.
- Make sure there's a sequence point between evaluation of the arguments
and the function body. Arguments should be evaluated before any memory
barriers.
- Fix use of __atomic_is_lock_free built-in. It requires the address of
an atomic variable as second argument. Use this built-in on clang as
well because clang's __c11_atomic_is_lock_free only takes the size of the
variable into account.
- In atomic_exchange_explicit put the barrier before instead of after the
__sync_lock_test_and_set call.
Reviewed by: theraven
In addition to testing against cxx_atomic, we must check c_atomic. The
former is only set when building C++ code. Also use __has_extension
instead of __has_feature. This allows us to use the atomics outside of
C11.
Reported by: Ariane van der Steldt <ariane stack nl>
PR: threads/170073
a c11 prefix to disambiguate them from the one provided by GCC.
Note: Clang 3.1 also supports the GCC builtins for libstdc++ 4.7 compatibility,
but I don't recommend using them because they are very poorly designed.
MFC after: 2 weeks
builtins, rather than the __asm hack. Somehow I missed the existence of this
builtin originally and only noticed that it was there when I went to implement
it...
Note: Trunk clang now has support for (most of) the C[++]11 atomics stuff.
Please test!
Approved by: brooks (mentor)
The development version of GCC also supports an atomics interface
similar to Clang's. Change the header file to work as follows:
- __CLANG_ATOMICS: Use Clang's new atomics interface,
- __GNUC_ATOMICS: Use GCC's new atomics interface,
- else: fall back to GCC's __sync interface.
- Make atomic_init() work for GCC, as assigning to structs doesn't work.
- Fix misplaced parenthesis in atomic_is_lock_free() for GCC.
- Make atomic_compare_exchange_strong() for GCC return the proper
boolean value, whether object == expected.
- Fix argument passing in atomic_exchange_explicit() for GCC.
tested) with clang and gcc, and more efficiently with clang+a big out-of-tree
diff that I need to commit soon (once it's been tidied and reviewed a bit).
Large portions by: ed
Reviewed by: ed
Approved by: dim (mentor)
