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getDefaultSubstituters(): Simplify initialisation

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As shlevy pointed out, static variables in C++11 have thread-safe
initialisation.
This commit is contained in:
Eelco Dolstra 2017-07-04 16:26:48 +02:00
parent 6cf23c3e8f
commit b7203e853e
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1 changed files with 14 additions and 20 deletions
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16
src/libstore/store-api.cc
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@ -795,22 +795,15 @@ static RegisterStoreImplementation regStore([](
std::list<ref<Store>> getDefaultSubstituters() std::list<ref<Store>> getDefaultSubstituters()
{ {
struct State { static auto stores([]() {
bool done = false;
std::list<ref<Store>> stores; std::list<ref<Store>> stores;
};
static Sync<State> state_;
auto state(state_.lock());
if (state->done) return state->stores;
StringSet done; StringSet done;
auto addStore = [&](const std::string & uri) { auto addStore = [&](const std::string & uri) {
if (done.count(uri)) return; if (done.count(uri)) return;
done.insert(uri); done.insert(uri);
state->stores.push_back(openStore(uri)); stores.push_back(openStore(uri));
}; };
for (auto uri : settings.substituters.get()) for (auto uri : settings.substituters.get())
@ -819,9 +812,10 @@ std::list<ref<Store>> getDefaultSubstituters()
for (auto uri : settings.extraSubstituters.get()) for (auto uri : settings.extraSubstituters.get())
addStore(uri); addStore(uri);
state->done = true; return stores;
} ());
return state->stores; return stores;
} }