使用命名管道在重定向的标准输出上永久阻止

We are trying to communicate between two processes via named pipes that are redirected to stdin and stdout in the child process. The parent process opens the named pipe and calls fdopen on them. The problem we see is that fwrite on this works, however even reading one byte from redirected stdout pipe blocks eternally. The code works when using the file descriptors instead of FILE *. What is wrong? Code is a little long, sorry.We are trying to communicate between two proces