[libc++] Introduce make_test_jthread for jthread tests (#68837)

This patch introduces the support::make_test_jthread utility which is
basically the same as support::make_test_thread but for std::jthread. It
allows vendors to maintain a downstream way to create threads for use
within the test suite, which is especially useful for embedded
platforms.

libcxx/test/std/thread/thread.jthread/assign.move.pass.cpp

@@ -23,30 +23,31 @@
 #include <utility>
 #include <vector>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(std::is_nothrow_move_assignable_v<std::jthread>);
 
 int main(int, char**) {
   // If &x == this is true, there are no effects.
   {
-    std::jthread j([] {});
-    auto id      = j.get_id();
-    auto ssource = j.get_stop_source();
-    j            = std::move(j);
+    std::jthread j = support::make_test_jthread([] {});
+    auto id        = j.get_id();
+    auto ssource   = j.get_stop_source();
+    j              = std::move(j);
     assert(j.get_id() == id);
     assert(j.get_stop_source() == ssource);
   }
 
   // if joinable() is true, calls request_stop() and then join()
   // request_stop is called
   {
-    std::jthread j1([] {});
-    bool called = false;
+    std::jthread j1 = support::make_test_jthread([] {});
+    bool called     = false;
     std::stop_callback cb(j1.get_stop_token(), [&called] { called = true; });
 
-    std::jthread j2([] {});
-    j1 = std::move(j2);
+    std::jthread j2 = support::make_test_jthread([] {});
+    j1              = std::move(j2);
     assert(called);
   }
 
@@ -58,10 +59,10 @@ int main(int, char**) {
     constexpr auto numberOfThreads = 10u;
     jts.reserve(numberOfThreads);
     for (auto i = 0u; i < numberOfThreads; ++i) {
-      jts.emplace_back([&] {
+      jts.emplace_back(support::make_test_jthread([&] {
         std::this_thread::sleep_for(std::chrono::milliseconds(2));
         calledTimes.fetch_add(1, std::memory_order_relaxed);
-      });
+      }));
     }
 
     for (auto i = 0u; i < numberOfThreads; ++i) {
@@ -79,10 +80,10 @@ int main(int, char**) {
 
   // then assigns the state of x to *this
   {
-    std::jthread j1([] {});
-    std::jthread j2([] {});
-    auto id2      = j2.get_id();
-    auto ssource2 = j2.get_stop_source();
+    std::jthread j1 = support::make_test_jthread([] {});
+    std::jthread j2 = support::make_test_jthread([] {});
+    auto id2        = j2.get_id();
+    auto ssource2   = j2.get_stop_source();
 
     j1 = std::move(j2);
 
@@ -92,9 +93,9 @@ int main(int, char**) {
 
   // sets x to a default constructed state
   {
-    std::jthread j1([] {});
-    std::jthread j2([] {});
-    j1 = std::move(j2);
+    std::jthread j1 = support::make_test_jthread([] {});
+    std::jthread j2 = support::make_test_jthread([] {});
+    j1              = std::move(j2);
 
     assert(j2.get_id() == std::jthread::id());
     assert(!j2.get_stop_source().stop_possible());
@@ -103,7 +104,7 @@ int main(int, char**) {
   // joinable is false
   {
     std::jthread j1;
-    std::jthread j2([] {});
+    std::jthread j2 = support::make_test_jthread([] {});
 
     auto j2Id = j2.get_id();
 

libcxx/test/std/thread/thread.jthread/cons.move.pass.cpp

@@ -19,6 +19,7 @@
 #include <type_traits>
 #include <utility>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(std::is_nothrow_move_constructible_v<std::jthread>);
@@ -27,8 +28,8 @@ int main(int, char**) {
   {
     // x.get_id() == id() and get_id() returns the value of x.get_id() prior
     // to the start of construction.
-    std::jthread j1{[] {}};
-    auto id1 = j1.get_id();
+    std::jthread j1 = support::make_test_jthread([] {});
+    auto id1        = j1.get_id();
 
     std::jthread j2(std::move(j1));
     assert(j1.get_id() == std::jthread::id());
@@ -38,8 +39,8 @@ int main(int, char**) {
   {
     // ssource has the value of x.ssource prior to the start of construction
     // and x.ssource.stop_possible() is false.
-    std::jthread j1{[] {}};
-    auto ss1 = j1.get_stop_source();
+    std::jthread j1 = support::make_test_jthread([] {});
+    auto ss1        = j1.get_stop_source();
 
     std::jthread j2(std::move(j1));
     assert(ss1 == j2.get_stop_source());

libcxx/test/std/thread/thread.jthread/detach.pass.cpp

@@ -23,17 +23,18 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 int main(int, char**) {
   // Effects: The thread represented by *this continues execution without the calling thread blocking.
   {
     std::atomic_bool start{false};
     std::atomic_bool done{false};
-    std::optional<std::jthread> jt{[&start, &done] {
+    std::optional<std::jthread> jt = support::make_test_jthread([&start, &done] {
       start.wait(false);
       done = true;
-    }};
+    });
 
     // If it blocks, it will deadlock here
     jt->detach();
@@ -49,7 +50,7 @@ int main(int, char**) {
 
   // Postconditions: get_id() == id().
   {
-    std::jthread jt{[] {}};
+    std::jthread jt = support::make_test_jthread([] {});
     assert(jt.get_id() != std::jthread::id());
     jt.detach();
     assert(jt.get_id() == std::jthread::id());

libcxx/test/std/thread/thread.jthread/dtor.pass.cpp

@@ -20,6 +20,8 @@
 #include <thread>
 #include <type_traits>
 #include <vector>
+
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 int main(int, char**) {
@@ -32,8 +34,8 @@ int main(int, char**) {
   // If joinable() is true, calls request_stop() and then join().
   // request_stop is called
   {
-    std::optional<std::jthread> jt([] {});
-    bool called = false;
+    std::optional<std::jthread> jt = support::make_test_jthread([] {});
+    bool called                    = false;
     std::stop_callback cb(jt->get_stop_token(), [&called] { called = true; });
     jt.reset();
     assert(called);
@@ -48,10 +50,10 @@ int main(int, char**) {
     constexpr auto numberOfThreads = 10u;
     jts.reserve(numberOfThreads);
     for (auto i = 0u; i < numberOfThreads; ++i) {
-      jts.emplace_back([&calledTimes] {
+      jts.emplace_back(support::make_test_jthread([&calledTimes] {
         std::this_thread::sleep_for(std::chrono::milliseconds{2});
         calledTimes.fetch_add(1, std::memory_order_relaxed);
-      });
+      }));
     }
     jts.clear();
 

libcxx/test/std/thread/thread.jthread/get_id.pass.cpp

@@ -18,6 +18,7 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(noexcept(std::declval<const std::jthread&>().get_id()));
@@ -32,7 +33,7 @@ int main(int, char**) {
 
   // Represents a thread
   {
-    const std::jthread jt{[] {}};
+    const std::jthread jt                                = support::make_test_jthread([] {});
     std::same_as<std::jthread::id> decltype(auto) result = jt.get_id();
     assert(result != std::jthread::id());
   }

libcxx/test/std/thread/thread.jthread/get_stop_source.pass.cpp

@@ -19,14 +19,15 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(noexcept(std::declval<std::jthread&>().get_stop_source()));
 
 int main(int, char**) {
   // Represents a thread
   {
-    std::jthread jt{[] {}};
+    std::jthread jt                                      = support::make_test_jthread([] {});
     std::same_as<std::stop_source> decltype(auto) result = jt.get_stop_source();
     assert(result.stop_possible());
   }

libcxx/test/std/thread/thread.jthread/get_stop_token.pass.cpp

@@ -20,14 +20,15 @@
 #include <type_traits>
 #include <utility>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(noexcept(std::declval<const std::jthread&>().get_stop_token()));
 
 int main(int, char**) {
   // Represents a thread
   {
-    std::jthread jt{[] {}};
+    std::jthread jt                                 = support::make_test_jthread([] {});
     auto ss                                         = jt.get_stop_source();
     std::same_as<std::stop_token> decltype(auto) st = std::as_const(jt).get_stop_token();
 

libcxx/test/std/thread/thread.jthread/join.deadlock.pass.cpp

@@ -31,6 +31,7 @@
 #include <type_traits>
 #include <vector>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 int main(int, char**) {
@@ -40,12 +41,12 @@ int main(int, char**) {
     std::atomic_bool start = false;
     std::atomic_bool done  = false;
 
-    std::jthread jt{[&] {
+    std::jthread jt = support::make_test_jthread([&] {
       start.wait(false);
       f();
       done = true;
       done.notify_all();
-    }};
+    });
 
     f = [&] {
       try {

libcxx/test/std/thread/thread.jthread/join.pass.cpp

@@ -23,6 +23,7 @@
 #include <type_traits>
 #include <vector>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 int main(int, char**) {
@@ -33,10 +34,10 @@ int main(int, char**) {
     constexpr auto numberOfThreads = 10u;
     jts.reserve(numberOfThreads);
     for (auto i = 0u; i < numberOfThreads; ++i) {
-      jts.emplace_back([&] {
+      jts.emplace_back(support::make_test_jthread([&] {
         std::this_thread::sleep_for(std::chrono::milliseconds(2));
         calledTimes.fetch_add(1, std::memory_order_relaxed);
-      });
+      }));
     }
 
     for (auto i = 0u; i < numberOfThreads; ++i) {
@@ -55,15 +56,15 @@ int main(int, char**) {
   // Synchronization: The completion of the thread represented by *this synchronizes with
   // ([intro.multithread]) the corresponding successful join() return.
   {
-    bool flag = false;
-    std::jthread jt{[&] { flag = true; }};
+    bool flag       = false;
+    std::jthread jt = support::make_test_jthread([&] { flag = true; });
     jt.join();
     assert(flag); // non atomic write is visible to the current thread
   }
 
   // Postconditions: The thread represented by *this has completed. get_id() == id().
   {
-    std::jthread jt{[] {}};
+    std::jthread jt = support::make_test_jthread([] {});
     assert(jt.get_id() != std::jthread::id());
     jt.join();
     assert(jt.get_id() == std::jthread::id());

libcxx/test/std/thread/thread.jthread/joinable.pass.cpp

@@ -19,6 +19,7 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(noexcept(std::declval<const std::jthread&>().joinable()));
@@ -33,16 +34,16 @@ int main(int, char**) {
 
   // Non-default constructed
   {
-    const std::jthread jt{[] {}};
+    const std::jthread jt                    = support::make_test_jthread([] {});
     std::same_as<bool> decltype(auto) result = jt.joinable();
     assert(result);
   }
 
   // Non-default constructed
   // the thread of execution has not finished
   {
-    std::atomic_bool done = false;
-    const std::jthread jt{[&done] { done.wait(false); }};
+    std::atomic_bool done                    = false;
+    const std::jthread jt                    = support::make_test_jthread([&done] { done.wait(false); });
     std::same_as<bool> decltype(auto) result = jt.joinable();
     done                                     = true;
     done.notify_all();

libcxx/test/std/thread/thread.jthread/request_stop.pass.cpp

@@ -19,15 +19,16 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 static_assert(noexcept(std::declval<std::jthread&>().request_stop()));
 
 int main(int, char**) {
   // Represents a thread
   {
-    std::jthread jt{[] {}};
-    auto st = jt.get_stop_token();
+    std::jthread jt = support::make_test_jthread([] {});
+    auto st         = jt.get_stop_token();
     assert(!st.stop_requested());
     std::same_as<bool> decltype(auto) result = jt.request_stop();
     assert(result);

libcxx/test/std/thread/thread.jthread/swap.free.pass.cpp

@@ -17,6 +17,7 @@
 #include <thread>
 #include <type_traits>
 
+#include "make_test_thread.h"
 #include "test_macros.h"
 
 template <class T>
@@ -30,7 +31,7 @@ int main(int, char**) {
   // x is default constructed
   {
     std::jthread t1;
-    std::jthread t2{[] {}};
+    std::jthread t2        = support::make_test_jthread([] {});
     const auto originalId2 = t2.get_id();
     swap(t1, t2);
 
@@ -40,7 +41,7 @@ int main(int, char**) {
 
   // y is default constructed
   {
-    std::jthread t1([] {});
+    std::jthread t1 = support::make_test_jthread([] {});
     std::jthread t2{};
     const auto originalId1 = t1.get_id();
     swap(t1, t2);
@@ -51,8 +52,8 @@ int main(int, char**) {
 
   // both not default constructed
   {
-    std::jthread t1([] {});
-    std::jthread t2{[] {}};
+    std::jthread t1        = support::make_test_jthread([] {});
+    std::jthread t2        = support::make_test_jthread([] {});
     const auto originalId1 = t1.get_id();
     const auto originalId2 = t2.get_id();
     swap(t1, t2);