test thread/fork speed; reset msg after release.

lichao

2021-03-26 d17450bd7bc9fd5e98e8e2f00999caffe2e301a6

 src/shm.h

@@ -88,7 +88,7 @@
    {
        pdata_ = shm_.find_or_construct<Data>(ObjName(name_).c_str(), std::nothrow)(t...);
        if (!IsOk()) {
            throw("shm error: " + name_);
            throw("Error: Not enough memory, can not allocate \"" + name_ + "\"");
        }
    }
    Data *find(const std::string &name) { return shm_.find<Data>(ObjName(name).c_str()).first; }