added semaphore and shared memory to print without superposition between parent and child process

srcs/utils.cpp

@@ -310,6 +310,49 @@ void	print_special(std::string str)
 	}
 }
 
+// https://stackoverflow.com/questions/5656530/how-to-use-shared-memory-with-linux-in-c
+void* create_shared_memory(size_t size) {
+	// Our memory buffer will be readable and writable:
+	int protection = PROT_READ | PROT_WRITE;
+
+	// The buffer will be shared (meaning other processes can access it), but
+	// anonymous (meaning third-party processes cannot obtain an address for it),
+	// so only this process and its children will be able to use it:
+	int visibility = MAP_SHARED | MAP_ANONYMOUS;
+
+	// The remaining parameters to `mmap()` are not important for this use case,
+	// but the manpage for `mmap` explains their purpose.
+	return mmap(NULL, size, protection, visibility, -1, 0);
+}
+
+void	init_semaphore()
+{
+	int	ret;
+
+	g_shmem = static_cast<sem_t*>(create_shared_memory(4));
+
+	ret = sem_init(g_shmem, 1, 1);
+	if (ret != 0)
+	{
+		perror("err sem_init()");
+		exit(EXIT_FAILURE);
+	}
+}
+
+void	print_secure(std::string message)
+{
+	sem_wait(g_shmem);
+	std::cerr << g_family << "| " << message;
+	sem_post(g_shmem);
+}
+
+void	print_secure(int fd, std::string message)
+{
+	sem_wait(g_shmem);
+	std::cerr << g_family << "| (" << std::setw(2) << fd << ") " << message;
+	sem_post(g_shmem);
+}
+
 // OVERLOADS
 
 bool	operator==(const listen_socket& lhs, int fd)