diff options
Diffstat (limited to 'zen/globals.h')
| -rw-r--r-- | zen/globals.h | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/zen/globals.h b/zen/globals.h index 4c1453a2..876d2598 100644 --- a/zen/globals.h +++ b/zen/globals.h @@ -21,8 +21,7 @@ Solve static destruction order fiasco by providing shared ownership and serializ => use trivially-destructible POD only!!! ATTENTION: function-static globals have the compiler generate "magic statics" == compiler-genenerated locking code which will crash or leak memory when accessed after global is "dead" - => "solved" by FunStatGlobal, but we can't have "too many" of these... -*/ + => "solved" by FunStatGlobal, but we can't have "too many" of these... */ class PodSpinMutex { @@ -33,7 +32,11 @@ public: bool isLocked(); private: - std::atomic_flag flag_; //= ATOMIC_FLAG_INIT; rely entirely on static zero-initialization! => avoid potential contention with worker thread during Global<> construction! + std::atomic_flag flag_; /* => avoid potential contention with worker thread during Global<> construction! + - "For an atomic_flag with static storage duration, this guarantees static initialization:" => just what the doctor ordered! + - "[default initialization] initializes std::atomic_flag to clear state" - since C++20 => + - "std::atomic_flag is [...] guaranteed to be lock-free" + - interestingly, is_trivially_constructible_v<> is false, thanks to constexpr! https://developercommunity.visualstudio.com/content/problem/416343/stdatomic-no-longer-is-trivially-constructible.html */ }; @@ -43,7 +46,7 @@ class Global //don't use for function-scope statics! public: Global() { - static_assert(std::is_trivially_constructible_v<Pod>&& std::is_trivially_destructible_v<Pod>, "this memory needs to live forever"); + static_assert(std::is_trivially_destructible_v<Pod>, "this memory needs to live forever"); assert(!pod_.spinLock.isLocked()); //we depend on static zero-initialization! assert(!pod_.inst); // } @@ -106,8 +109,7 @@ public: std::shared_ptr<T> get() { - static_assert(std::is_trivially_constructible_v<FunStatGlobal>&& - std::is_trivially_destructible_v<FunStatGlobal>, "this class must not generate code for magic statics!"); + static_assert(std::is_trivially_destructible_v<FunStatGlobal>, "this class must not generate code for magic statics!"); pod_.spinLock.lock(); ZEN_ON_SCOPE_EXIT(pod_.spinLock.unlock()); @@ -184,8 +186,7 @@ void registerGlobalForDestruction(CleanUpEntry& entry) CleanUpEntry* head; } cleanUpList; - static_assert(std::is_trivially_constructible_v<decltype(cleanUpList)>&& - std::is_trivially_destructible_v<decltype(cleanUpList)>, "we must not generate code for magic statics!"); + static_assert(std::is_trivially_destructible_v<decltype(cleanUpList)>, "we must not generate code for magic statics!"); cleanUpList.spinLock.lock(); ZEN_ON_SCOPE_EXIT(cleanUpList.spinLock.unlock()); |