convert pid_t to const char* with stringstream

Question

I want to convert a process pid to a const char* but below does not work:

            std::ostringstream str_pid;
        str_pid << getpid();
        const char * cstr_pid = str_pid.str().c_str();

It works most of the time but sometimes it has a false result. Apparently i am doing something wrong. Any idea?

Answer 1

cstr_pid will be a dangling pointer, as the temporary std::string returned by str_pid.str() is destructed after the assignment of cstr_pid . Create a copy of the str_pid.str() return value:

const std::string my_pid(str_pid.str());

then use my_pid.c_str() when const char* is required.