open的时候不存在共享内存，则返回false，没有必要报错

Author: Aengus.Jiang

src/libipc/platform/posix/shm_posix.cpp

@@ -72,7 +72,9 @@ id_t acquire(char const * name, std::size_t size, unsigned mode) {
                                                S_IRGRP | S_IWGRP | 
                                                S_IROTH | S_IWOTH);
     if (fd == -1) {
-        ipc::error("fail shm_open[%d]: %s\n", errno, op_name.c_str());
+        if (open != mode) {
+            ipc::error("fail shm_open[%d]: %s\n", errno, op_name.c_str());
+        }
         return nullptr;
     }
     ::fchmod(fd, S_IRUSR | S_IWUSR | 

src/libipc/shm.cpp

@@ -78,8 +78,12 @@ bool handle::acquire(char const * name, std::size_t size, unsigned mode) {
         return false;
     }
     release();
+    const auto id = shm::acquire(name, size, mode);
+    if (!id) {
+        return false;
+    }
+    impl(p_)->id_ = id;
     impl(p_)->n_  = name;
-    impl(p_)->id_ = shm::acquire(name, size, mode);
     impl(p_)->m_  = shm::get_mem(impl(p_)->id_, &(impl(p_)->s_));
     return valid();
 }