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Fix single-threaded build for targets without atomics 

* src/c++17/memory_resource.cc [!_GLIBCXX_HAS_GTHREADS]
	(atomic_mem_res): Add unsynchronized definition for single-threaded.

From-SVN: r263554
This commit is contained in:
Jonathan Wakely 2018-08-15 10:56:33 +01:00 committed by Jonathan Wakely
parent 89bcf3fffe
commit 25b030b85a
2 changed files with 26 additions and 1 deletions
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5
libstdc++-v3/ChangeLog
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@ -1,3 +1,8 @@
2018-08-15 Jonathan Wakely <jwakely@redhat.com>
* src/c++17/memory_resource.cc [!_GLIBCXX_HAS_GTHREADS]
(atomic_mem_res): Add unsynchronized definition for single-threaded.
2018-08-14 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/86954

22
libstdc++-v3/src/c++17/memory_resource.cc
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@ -88,7 +88,7 @@ namespace pmr
#if ATOMIC_POINTER_LOCK_FREE == 2
using atomic_mem_res = atomic<memory_resource*>;
# define _GLIBCXX_ATOMIC_MEM_RES_CAN_BE_CONSTANT_INITIALIZED
#else
#elif defined(_GLIBCXX_HAS_GTHREADS)
// Can't use pointer-width atomics, define a type using a mutex instead:
struct atomic_mem_res
{
@ -114,6 +114,26 @@ namespace pmr
return std::exchange(val, r);
}
};
#else
# define _GLIBCXX_ATOMIC_MEM_RES_CAN_BE_CONSTANT_INITIALIZED
// Single-threaded, no need for synchronization
struct atomic_mem_res
{
constexpr
atomic_mem_res(memory_resource* r) : val(r) { }
memory_resource* val;
memory_resource* load() const
{
return val;
}
memory_resource* exchange(memory_resource* r)
{
return std::exchange(val, r);
}
};
#endif // ATOMIC_POINTER_LOCK_FREE == 2
#ifdef _GLIBCXX_ATOMIC_MEM_RES_CAN_BE_CONSTANT_INITIALIZED