diff --git a/CMakeLists.txt b/CMakeLists.txt
index b4845b0..6d9b2a5 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,7 +13,7 @@ if(NOT MSVC)
     set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
-if (MSVC AND LIBIPC_USE_STATIC_CRT)
+if (MSVC)
     set(CompilerFlags
         CMAKE_CXX_FLAGS
         CMAKE_CXX_FLAGS_DEBUG
@@ -22,9 +22,17 @@ if (MSVC AND LIBIPC_USE_STATIC_CRT)
         CMAKE_C_FLAGS_DEBUG
         CMAKE_C_FLAGS_RELEASE
         )
-    foreach(CompilerFlag ${CompilerFlags})
-        string(REPLACE "/MD" "/MT" ${CompilerFlag} "${${CompilerFlag}}")
-    endforeach()
+    if (LIBIPC_USE_STATIC_CRT)
+        foreach(CompilerFlag ${CompilerFlags})
+            string(REPLACE "/MD" "/MT" ${CompilerFlag} "${${CompilerFlag}}")
+            string(REPLACE "/MDd" "/MTd" ${CompilerFlag} "${${CompilerFlag}}")
+        endforeach()
+    else()
+        foreach(CompilerFlag ${CompilerFlags})
+            string(REPLACE "/MT" "/MD" ${CompilerFlag} "${${CompilerFlag}}")
+            string(REPLACE "/MTd" "/MDd" ${CompilerFlag} "${${CompilerFlag}}")
+        endforeach()
+    endif()
 endif()
 
 set(LIBRARY_OUTPUT_PATH    ${CMAKE_BINARY_DIR}/bin)
@@ -50,6 +58,7 @@ endif()
 if (LIBIPC_BUILD_DEMOS)
     add_subdirectory(demo/chat)
     add_subdirectory(demo/msg_que)
+    add_subdirectory(demo/send_recv)
 endif()
 
 install(
diff --git a/demo/msg_que/main.cpp b/demo/msg_que/main.cpp
index 5635101..27c5ce6 100644
--- a/demo/msg_que/main.cpp
+++ b/demo/msg_que/main.cpp
@@ -127,10 +127,10 @@ int main(int argc, char ** argv) {
     ::signal(SIGHUP  , exit);
 #endif
 
-    if (std::string{ argv[1] } == mode_s__) {
+    std::string mode {argv[1]};
+    if (mode == mode_s__) {
         do_send();
-    }
-    else if (std::string{ argv[1] } == mode_r__) {
+    } else if (mode == mode_r__) {
         do_recv();
     }
     return 0;
diff --git a/demo/send_recv/CMakeLists.txt b/demo/send_recv/CMakeLists.txt
new file mode 100644
index 0000000..9d3f0fb
--- /dev/null
+++ b/demo/send_recv/CMakeLists.txt
@@ -0,0 +1,11 @@
+project(send_recv)
+
+include_directories(
+    ${LIBIPC_PROJECT_DIR}/3rdparty)
+
+file(GLOB SRC_FILES ./*.cpp)
+file(GLOB HEAD_FILES ./*.h)
+
+add_executable(${PROJECT_NAME} ${SRC_FILES} ${HEAD_FILES})
+
+target_link_libraries(${PROJECT_NAME} ipc)
diff --git a/demo/send_recv/main.cpp b/demo/send_recv/main.cpp
new file mode 100644
index 0000000..3acc52a
--- /dev/null
+++ b/demo/send_recv/main.cpp
@@ -0,0 +1,46 @@
+
+#include <iostream>
+#include <string>
+#include <thread>
+#include <chrono>
+
+#include "libipc/ipc.h"
+
+namespace {
+
+void do_send(int size, int interval) {
+    ipc::channel ipc {"ipc", ipc::sender};
+    std::string buffer(size, 'A');
+    while (true) {
+        std::cout << "send size: " << buffer.size() + 1 << "\n";
+        ipc.send(buffer, 0/*tm*/);
+        std::this_thread::sleep_for(std::chrono::milliseconds(interval));
+    }
+}
+
+void do_recv(int interval) {
+    ipc::channel ipc {"ipc", ipc::receiver};
+    while (true) {
+        ipc::buff_t recv;
+        for (int k = 1; recv.empty(); ++k) {
+            std::cout << "recv waiting... " << k << "\n";
+            recv = ipc.recv(interval);
+        }
+        std::cout << "recv size: " << recv.size() << "\n";
+    }
+}
+
+} // namespace
+
+int main(int argc, char ** argv) {
+    if (argc < 3) return -1;
+    std::string mode {argv[1]};
+    if (mode == "send") {
+        if (argc < 4) return -1;
+        do_send(std::stoi(argv[2]) /*size*/, 
+                std::stoi(argv[3]) /*interval*/);
+    } else if (mode == "recv") {
+        do_recv(std::stoi(argv[2]) /*interval*/);
+    }
+    return 0;
+}
diff --git a/src/libipc/platform/waiter_linux.h b/src/libipc/platform/waiter_linux.h
index 006ba6a..fffe8d1 100755
--- a/src/libipc/platform/waiter_linux.h
+++ b/src/libipc/platform/waiter_linux.h
@@ -223,8 +223,6 @@ public:
     static bool wait(handle_t h, std::uint64_t tm = invalid_value) {
         if (h == invalid()) return false;
         switch (tm) {
-        case 0:
-            return true;
         case invalid_value:
             IPC_SEMAPHORE_FUNC_(sem_wait, h);
         default: {
diff --git a/src/libipc/waiter_helper.h b/src/libipc/waiter_helper.h
index 7bc6a08..39031f1 100644
--- a/src/libipc/waiter_helper.h
+++ b/src/libipc/waiter_helper.h
@@ -13,7 +13,7 @@ namespace detail {
 struct waiter_helper {
 
     struct wait_counter {
-        std::atomic<unsigned> waiting_ { 0 };
+        std::atomic<long> waiting_ { 0 };
         long counter_ = 0;
     };
 
@@ -33,14 +33,18 @@ struct waiter_helper {
         auto & counter = ctrl.counter();
         counter.waiting_.fetch_add(1, std::memory_order_release);
         flags.is_waiting_.store(true, std::memory_order_relaxed);
-        auto finally = ipc::guard([&counter, &flags] {
-            counter.waiting_.fetch_sub(1, std::memory_order_release);
+        auto finally = ipc::guard([&ctrl, &counter, &flags] {
+            for (auto curr_wait = counter.waiting_.load(std::memory_order_relaxed); curr_wait > 0;) {
+                if (counter.waiting_.compare_exchange_weak(curr_wait, curr_wait - 1, std::memory_order_acq_rel)) {
+                    break;
+                }
+            }
             flags.is_waiting_.store(false, std::memory_order_relaxed);
         });
         {
             IPC_UNUSED_ auto guard = ctrl.get_lock();
             if (!std::forward<F>(pred)()) return true;
-            counter.counter_ += 1;
+            counter.counter_ = counter.waiting_.load(std::memory_order_relaxed);
         }
         mtx.unlock();
 
@@ -69,6 +73,11 @@ struct waiter_helper {
         return ret;
     }
 
+    template <typename Ctrl>
+    static void clear_handshake(Ctrl & ctrl) {
+        while (ctrl.handshake_wait(0)) ;
+    }
+
     template <typename Ctrl>
     static bool notify(Ctrl & ctrl) {
         auto & counter = ctrl.counter();
@@ -77,6 +86,7 @@ struct waiter_helper {
         }
         bool ret = true;
         IPC_UNUSED_ auto guard = ctrl.get_lock();
+        clear_handshake(ctrl);
         if (counter.counter_ > 0) {
             ret = ctrl.sema_post(1);
             counter.counter_ -= 1;
@@ -93,12 +103,15 @@ struct waiter_helper {
         }
         bool ret = true;
         IPC_UNUSED_ auto guard = ctrl.get_lock();
+        clear_handshake(ctrl);
         if (counter.counter_ > 0) {
             ret = ctrl.sema_post(counter.counter_);
+            auto tm = default_timeout / counter.counter_;
             do {
                 counter.counter_ -= 1;
-                ret = ret && ctrl.handshake_wait(default_timeout);
+                ret = ret && ctrl.handshake_wait(tm);
             } while (counter.counter_ > 0);
+            counter.waiting_.store(0, std::memory_order_release);
         }
         return ret;
     }
@@ -116,6 +129,7 @@ struct waiter_helper {
         }
         bool ret = true;
         IPC_UNUSED_ auto guard = ctrl.get_lock();
+        clear_handshake(ctrl);
         if (counter.counter_ > 0) {
             ret = ctrl.sema_post(counter.counter_);
             counter.counter_ -= 1;
diff --git a/test/test_ipc.cpp b/test/test_ipc.cpp
index 16c076c..79f3b26 100755
--- a/test/test_ipc.cpp
+++ b/test/test_ipc.cpp
@@ -18,8 +18,9 @@ using namespace ipc;
 
 namespace {
 
-constexpr int LoopCount = 10000;
-constexpr int MultiMax  = 8;
+constexpr int LoopCount   = 10000;
+constexpr int MultiMax    = 8;
+constexpr int TestBuffMax = 65536;
 
 struct msg_head {
     int id_;
@@ -28,7 +29,7 @@ struct msg_head {
 class rand_buf : public buffer {
 public:
     rand_buf() {
-        int size = capo::random<>{sizeof(msg_head), 65536}();
+        int size = capo::random<>{sizeof(msg_head), TestBuffMax}();
         *this = buffer(new char[size], size, [](void * p, std::size_t) {
             delete [] static_cast<char *>(p);
         });
@@ -98,6 +99,22 @@ public:
     }
 } const data_set__;
 
+#define IPC_ASSERT_TRUE(condition) \
+    do { \
+        bool check = !!(condition); \
+        GTEST_TEST_BOOLEAN_(check, #condition, false, true, \
+                            GTEST_NONFATAL_FAILURE_); \
+        if (!check) return; \
+    } while (0)
+
+#define IPC_ASSERT_FALSE(condition) \
+    do { \
+        bool check = !!(condition); \
+        GTEST_TEST_BOOLEAN_(!check, #condition, true, false, \
+                            GTEST_NONFATAL_FAILURE_); \
+        if (check) return; \
+    } while (0)
+
 template <relat Rp, relat Rc, trans Ts, typename Que = chan<Rp, Rc, Ts>>
 void test_sr(char const * name, int s_cnt, int r_cnt) {
     ipc_ut::sender().start(static_cast<std::size_t>(s_cnt));
@@ -109,10 +126,10 @@ void test_sr(char const * name, int s_cnt, int r_cnt) {
     for (int k = 0; k < s_cnt; ++k) {
         ipc_ut::sender() << [name, &sw, r_cnt, k] {
             Que que { name, ipc::sender };
-            EXPECT_TRUE(que.wait_for_recv(r_cnt));
+            IPC_ASSERT_TRUE(que.wait_for_recv(r_cnt));
             sw.start();
             for (int i = 0; i < (int)data_set__.get().size(); ++i) {
-                EXPECT_TRUE(que.send(data_set__.get()[i]));
+                IPC_ASSERT_TRUE(que.send(data_set__.get()[i]));
             }
         };
     }
@@ -122,17 +139,17 @@ void test_sr(char const * name, int s_cnt, int r_cnt) {
             Que que { name, ipc::receiver };
             for (;;) {
                 rand_buf got { que.recv() };
-                ASSERT_FALSE(got.empty());
+                IPC_ASSERT_FALSE(got.empty());
                 int i = got.get_id();
                 if (i == -1) {
                     return;
                 }
-                ASSERT_TRUE((i >= 0) && (i < (int)data_set__.get().size()));
+                IPC_ASSERT_TRUE((i >= 0) && (i < (int)data_set__.get().size()));
                 auto const &data_set = data_set__.get()[i];
                 if (data_set != got) {
                     printf("data_set__.get()[%d] != got, size = %zd/%zd\n", 
                             i, data_set.size(), got.size());
-                    EXPECT_TRUE(false);
+                    IPC_ASSERT_TRUE(false);
                 }
             }
         };
@@ -140,7 +157,7 @@ void test_sr(char const * name, int s_cnt, int r_cnt) {
 
     ipc_ut::sender().wait_for_done();
     Que que { name };
-    EXPECT_TRUE(que.wait_for_recv(r_cnt));
+    IPC_ASSERT_TRUE(que.wait_for_recv(r_cnt));
     for (int k = 0; k < r_cnt; ++k) {
         que.send(rand_buf{msg_head{-1}});
     }
diff --git a/test/test_queue.cpp b/test/test_queue.cpp
index a59b3a7..e85d39f 100755
--- a/test/test_queue.cpp
+++ b/test/test_queue.cpp
@@ -103,7 +103,7 @@ void test_sr(elems_t<Rp, Rc, Ts> && elems, int s_cnt, int r_cnt, char const * me
             queue_t<Rp, Rc, Ts> que { &elems };
             ASSERT_TRUE(que.connect());
             while (pop(que).pid_ >= 0) ;
-            EXPECT_TRUE(que.disconnect());
+            ASSERT_TRUE(que.disconnect());
         };
     }
 
@@ -133,7 +133,7 @@ TEST(Queue, el_connection) {
         elems_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> el;
         EXPECT_TRUE(el.connect_sender());
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_FALSE(el.connect_sender());
+            ASSERT_FALSE(el.connect_sender());
         }
         el.disconnect_sender();
         EXPECT_TRUE(el.connect_sender());
@@ -141,7 +141,7 @@ TEST(Queue, el_connection) {
     {
         elems_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::unicast> el;
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_TRUE(el.connect_sender());
+            ASSERT_TRUE(el.connect_sender());
         }
     }
     {
@@ -149,7 +149,7 @@ TEST(Queue, el_connection) {
         auto cc = el.connect_receiver();
         EXPECT_NE(cc, 0);
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_EQ(el.connect_receiver(), 0);
+            ASSERT_EQ(el.connect_receiver(), 0);
         }
         EXPECT_EQ(el.disconnect_receiver(cc), 0);
         EXPECT_EQ(el.connect_receiver(), cc);
@@ -157,10 +157,10 @@ TEST(Queue, el_connection) {
     {
         elems_t<ipc::relat::single, ipc::relat::multi, ipc::trans::broadcast> el;
         for (std::size_t i = 0; i < (sizeof(ipc::circ::cc_t) * CHAR_BIT); ++i) {
-            EXPECT_NE(el.connect_receiver(), 0);
+            ASSERT_NE(el.connect_receiver(), 0);
         }
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_EQ(el.connect_receiver(), 0);
+            ASSERT_EQ(el.connect_receiver(), 0);
         }
     }
 }
@@ -171,11 +171,11 @@ TEST(Queue, connection) {
         queue_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> que{&el};
         // sending
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_TRUE(que.ready_sending());
+            ASSERT_TRUE(que.ready_sending());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> que{&el};
-            EXPECT_FALSE(que.ready_sending());
+            ASSERT_FALSE(que.ready_sending());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             que.shut_sending();
@@ -186,15 +186,15 @@ TEST(Queue, connection) {
         }
         // receiving
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_TRUE(que.connect());
+            ASSERT_TRUE(que.connect());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> que{&el};
-            EXPECT_FALSE(que.connect());
+            ASSERT_FALSE(que.connect());
         }
         EXPECT_TRUE(que.disconnect());
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_FALSE(que.disconnect());
+            ASSERT_FALSE(que.disconnect());
         }
         {
             queue_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> que{&el};
@@ -202,7 +202,7 @@ TEST(Queue, connection) {
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::single, ipc::relat::single, ipc::trans::unicast> que{&el};
-            EXPECT_FALSE(que.connect());
+            ASSERT_FALSE(que.connect());
         }
     }
     {
@@ -210,42 +210,42 @@ TEST(Queue, connection) {
         queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
         // sending
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_TRUE(que.ready_sending());
+            ASSERT_TRUE(que.ready_sending());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_TRUE(que.ready_sending());
+            ASSERT_TRUE(que.ready_sending());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             que.shut_sending();
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_TRUE(que.ready_sending());
+            ASSERT_TRUE(que.ready_sending());
         }
         // receiving
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_TRUE(que.connect());
+            ASSERT_TRUE(que.connect());
         }
         for (std::size_t i = 1; i < (sizeof(ipc::circ::cc_t) * CHAR_BIT); ++i) {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_TRUE(que.connect());
+            ASSERT_TRUE(que.connect());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_FALSE(que.connect());
+            ASSERT_FALSE(que.connect());
         }
-        EXPECT_TRUE(que.disconnect());
+        ASSERT_TRUE(que.disconnect());
         for (std::size_t i = 0; i < 10000; ++i) {
-            EXPECT_FALSE(que.disconnect());
+            ASSERT_FALSE(que.disconnect());
         }
         {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_TRUE(que.connect());
+            ASSERT_TRUE(que.connect());
         }
         for (std::size_t i = 0; i < 10000; ++i) {
             queue_t<ipc::relat::multi, ipc::relat::multi, ipc::trans::broadcast> que{&el};
-            EXPECT_FALSE(que.connect());
+            ASSERT_FALSE(que.connect());
         }
     }
 }