+void model_assert(bool expr, const char *file, int line)
+{
+ if (!expr) {
+ char msg[100];
+ sprintf(msg, "Program has hit assertion in file %s at line %d\n",
+ file, line);
+ model->assert_user_bug(msg);
+ }
+}
+
+#ifndef CONFIG_DEBUG
+
+static int fd_user_out; /**< @brief File descriptor from which to read user program output */
+
+/**
+ * @brief Setup output redirecting
+ *
+ * Redirects user program's stdout to a pipe so that we can dump it
+ * selectively, when displaying bugs, etc.
+ * Also connects a file descriptor 'model_out' directly to stdout, for printing
+ * data when needed.
+ *
+ * The model-checker can selectively choose to print/hide the user program
+ * output.
+ * @see clear_program_output
+ * @see print_program_output
+ *
+ * Note that the user program's pipe has limited memory, so if a program will
+ * output much data, we will need to buffer it in user-space during execution.
+ * This also means that if ModelChecker decides not to print an execution, it
+ * should promptly clear the pipe.
+ *
+ * This function should only be called once.
+ */
+void redirect_output()
+{
+ /* Save stdout for later use */
+ model_out = dup(STDOUT_FILENO);
+ if (model_out < 0) {
+ perror("dup");
+ exit(EXIT_FAILURE);
+ }
+
+ /* Redirect program output to a pipe */
+ int pipefd[2];
+ if (pipe(pipefd) < 0) {
+ perror("pipe");
+ exit(EXIT_FAILURE);
+ }
+ if (dup2(pipefd[1], STDOUT_FILENO) < 0) {
+ perror("dup2");
+ exit(EXIT_FAILURE);
+ }
+ close(pipefd[1]);
+
+ /* Save the "read" side of the pipe for use later */
+ if (fcntl(pipefd[0], F_SETFL, O_NONBLOCK) < 0) {
+ perror("fcntl");
+ exit(EXIT_FAILURE);
+ }
+ fd_user_out = pipefd[0];
+}
+
+/**
+ * @brief Wrapper for reading data to buffer
+ *
+ * Besides a simple read, this handles the subtleties of EOF and nonblocking
+ * input (if fd is O_NONBLOCK).
+ *
+ * @param fd The file descriptor to read.
+ * @param buf Buffer to read to.
+ * @param maxlen Maximum data to read to buffer
+ * @return The length of data read. If zero, then we hit EOF or ran out of data
+ * (non-blocking)
+ */
+static ssize_t read_to_buf(int fd, char *buf, size_t maxlen)
+{
+ ssize_t ret = read(fd, buf, maxlen);
+ if (ret < 0) {
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ return 0;
+ } else {
+ perror("read");
+ exit(EXIT_FAILURE);
+ }
+ }
+ return ret;
+}
+
+/** @brief Dump any pending program output without printing */
+void clear_program_output()