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#include <library/cpp/containers/cow_string/cow_string.h>
#include <library/cpp/testing/unittest/registar.h>
#include <util/generic/strbuf.h>
#include <util/generic/yexception.h>
#include <util/stream/output.h>
#include <util/system/thread.h>
#include <string>
#include <barrier>
static_assert(sizeof(TCowString) == sizeof(const char*), "expect sizeof(TCowString) == sizeof(const char*)");
Y_UNIT_TEST_SUITE(CowPitfalls) {
Y_UNIT_TEST(ParallelDetach) {
// best results with thread-sanitizer
std::vector<std::unique_ptr<TThread>> threads;
TCowString a = "the string";
TCowString b = a;
auto makeRefToA = [&a, &b]() {
b = a; // make second reference to the same string
};
constexpr int nThreads = 8;
#ifdef _tsan_enabled_
constexpr i64 retries = 1'000;
#else
constexpr i64 retries = 1'000'000;
#endif
std::barrier iterationSyncPoint(nThreads, makeRefToA);
std::atomic<i64> totalLen = 0;
auto addLen = [](std::string a, std::atomic<i64>& len) {
len += a.length();
};
auto workload = [&a, &addLen, &totalLen, &iterationSyncPoint]() {
std::atomic<i64> len = 0;
for (i64 j = 0; j < retries; ++j) {
addLen(a, len); // possibility of bad implicit conversion
iterationSyncPoint.arrive_and_wait();
}
totalLen += len.load();
};
for (int i = 0; i < nThreads; ++i) {
threads.push_back(std::make_unique<TThread>(workload));
}
for (auto& t : threads) {
t->Start();
}
for (auto& t : threads) {
t->Join();
}
UNIT_ASSERT_VALUES_EQUAL(totalLen.load(), b.size() * nThreads * retries);
}
} // Y_UNIT_TEST_SUITE(CowPitfalls)
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