fix: handle polls with both POLLIN and POLLHUP (#9)

The behaviour of poll() seems to differ between Linux and Darwin when the
child process has closed the pipe and poll() returns both POLLIN and POLLHUP
set on the returned events value. On Linux this is a sign that we can read
from the pipe one more time, but on Darwin it seems that POLLIN remains set
after the final read so we need to add extra logic to make sure to stop
polling for POLLIN after a failed read in the presence of POLLHUP.

Also fix minor formatting issues introduced by Devin.

Author: limeytexan

t3.c

@@ -185,8 +185,9 @@ void timestamp_and_send(int pipe_fd, int fd, const char *prefix) {
 
   // Send a message to the parent process to indicate that the child
   // process has started
-  if (snprintf(msg_payload.text, BUFFER_SIZE, "%s started", prefix) >= BUFFER_SIZE) { // NOLINT
-      _error("Message truncated in timestamp_and_send");
+  if (snprintf(msg_payload.text, BUFFER_SIZE, "%s started", prefix) >=
+      BUFFER_SIZE) { // NOLINT
+    _error("Message truncated in timestamp_and_send");
   }
   msg_payload.timestamp.tv_sec = 0;
   msg_payload.timestamp.tv_nsec = 0;
@@ -309,9 +310,10 @@ void process_msg_payload(FILE *stream, FILE *logfile, const char *color,
       int hours = elapsed_sec / 3600;
       int minutes = (elapsed_sec % 3600) / 60;
       int seconds = elapsed_sec % 60;
-      if (snprintf(timestamp, sizeof(timestamp), "%02d:%02d:%02d.%06ld ", hours, minutes, seconds, // NOLINT
-              (elapsed_nsec / 1000)) >= sizeof(timestamp)) {
-          _error("Timestamp truncated in process_msg_payload");
+      if (snprintf(timestamp, sizeof(timestamp), "%02d:%02d:%02d.%06ld ", hours,
+                   minutes, seconds, // NOLINT
+                   (elapsed_nsec / 1000)) >= sizeof(timestamp)) {
+        _error("Timestamp truncated in process_msg_payload");
       }
     } else {
       struct tm *time_info = localtime(&msg_payload->timestamp.tv_sec);
@@ -326,8 +328,8 @@ void process_msg_payload(FILE *stream, FILE *logfile, const char *color,
       size_t current_len = strlen(timestamp);
       size_t remaining = sizeof(timestamp) - current_len;
       if (snprintf(timestamp + current_len, remaining, ".%06ld ", // NOLINT
-              msg_payload->timestamp.tv_nsec / 1000) >= remaining) {
-          _error("Nanoseconds truncated in process_msg_payload");
+                   msg_payload->timestamp.tv_nsec / 1000) >= remaining) {
+        _error("Nanoseconds truncated in process_msg_payload");
       }
     }
   } else {
@@ -607,9 +609,9 @@ int main(int argc, char *argv[]) {
   struct pollfd pfds[2];
   nfds_t num_open_fds = 2; // We start with two open file descriptors
   pfds[0].fd = stdout_msg_pipe[0];
-  pfds[0].events = POLLIN;
+  pfds[0].events = POLLIN | POLLHUP;
   pfds[1].fd = stderr_msg_pipe[0];
-  pfds[1].events = POLLIN;
+  pfds[1].events = POLLIN | POLLHUP;
 
   int loopcount = 0;
   int ms_delta = 0;
@@ -650,7 +652,13 @@ int main(int argc, char *argv[]) {
             msg->msg_payload = msg_payload;
             push(&stdout_head, &stdout_tail, msg, &stdout_queuelen);
           } else {
-            perror("read(stdout_msg_pipe[0])");
+            if (pfds[0].revents & POLLHUP) {
+              // POLLIN and POLLHUP both set, but reads are failing
+              // so stop polling for POLLIN events.
+              pfds[0].events = POLLHUP;
+            } else {
+              perror("read(stdout_msg_pipe[0])");
+            }
           }
         } else if (pfds[0].revents & POLLHUP) {
           _debug(2, "closing stdout_msg_pipe[0]");
@@ -669,7 +677,13 @@ int main(int argc, char *argv[]) {
             msg->msg_payload = msg_payload;
             push(&stderr_head, &stderr_tail, msg, &stderr_queuelen);
           } else {
-            perror("read(stderr_msg_pipe[0])");
+            if (pfds[1].revents & POLLHUP) {
+              // POLLIN and POLLHUP both set, but reads are failing
+              // so stop polling for POLLIN events.
+              pfds[1].events = POLLHUP;
+            } else {
+              perror("read(stderr_msg_pipe[0])");
+            }
           }
         } else if (pfds[1].revents & POLLHUP) {
           _debug(2, "closing stderr_msg_pipe[0]");