Improved error handling

Fixes a memory leak and avoids aggressive busy looping when problems
accessing tty device.

src/Makefile.am

@@ -4,11 +4,13 @@ tio_SOURCES = tty.c \
               time.c \
               main.c \
               log.c \
+              error.c \
               include/tio/tty.h \
               include/tio/options.h \
               include/tio/time.h \
               include/tio/print.h \
-                include/tio/log.h
+              include/tio/log.h \
+              include/tio/error.h
 
 if ENABLE_BASH_COMPLETION
 bashcompletiondir=@BASH_COMPLETION_DIR@

src/error.c

@@ -0,0 +1,35 @@
+/*
+ * tio - the simple TTY terminal I/O application
+ *
+ * Copyright (c) 2014-2016  Martin Lund
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include "tio/options.h"
+#include "tio/print.h"
+
+char *error = "";
+
+void error_exit(void)
+{
+    if ((error[0] != 0) && (option.no_autoconnect))
+        printf("Error: %s\n", error);
+}

src/include/tio/error.h

@@ -0,0 +1,32 @@
+/*
+ * tio - the simple TTY terminal I/O application
+ *
+ * Copyright (c) 2014-2016  Martin Lund
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef ERROR_H
+#define ERROR_H
+
+#define TIO_SUCCESS 0
+#define TIO_ERROR   1
+
+extern char *error;
+
+void error_exit(void);
+
+#endif

src/main.c

@@ -21,9 +21,12 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "tio/options.h"
 #include "tio/tty.h"
 #include "tio/log.h"
+#include "tio/error.h"
+#include "tio/print.h"
 
 int main(int argc, char *argv[])
 {
@@ -35,6 +38,9 @@ int main(int argc, char *argv[])
     /* Configure output terminal */
     configure_stdout();
 
+    /* Install error exit handler */
+    atexit(&error_exit);
+
     /* Install log exit handler */
     atexit(&log_exit);
 

src/tty.c

@@ -36,6 +36,7 @@
 #include "tio/options.h"
 #include "tio/time.h"
 #include "tio/log.h"
+#include "tio/error.h"
 
 static int connected = false;
 struct termios new_stdout, old_stdout, old_tio;
@@ -44,22 +45,27 @@ static bool tainted = false;
 
 void wait_for_tty_device(void)
 {
-    int ready, n;
-    struct stat status;
     fd_set rdfs;
+    int    ready, status;
     struct timeval tv;
-    char c_stdin[3];
+    static char c_stdin[3];
+    static bool first = true;
 
     /* Loop until device pops up */
     while (true)
     {
-        /* Test for accessible device file */
-        if (access(option.tty_device, R_OK) == 0)
-            return;
-
+        if (first)
+        {
+            /* Don't wait first time */
+            tv.tv_sec = 0;
+            tv.tv_usec = 1;
+            first = false;
+        } else
+        {
             /* Wait up to 1 second */
             tv.tv_sec = 1;
             tv.tv_usec = 0;
+        }
 
         FD_ZERO(&rdfs);
         FD_SET(STDIN_FILENO, &rdfs);
@@ -71,7 +77,9 @@ void wait_for_tty_device(void)
             /* Input from stdin ready */
 
             /* Read one character */
-            n = read(STDIN_FILENO, &c_stdin[0], 1);
+            status = read(STDIN_FILENO, &c_stdin[0], 1);
+            if (status < 0)
+                printf("Warning: Could not read from stdin\n");
 
             /* Exit upon ctrl-t + q sequence */
             c_stdin[2] = c_stdin[1];
@@ -79,6 +87,10 @@ void wait_for_tty_device(void)
             if ((c_stdin[1] == KEY_Q) && (c_stdin[2] == KEY_CTRL_T))
                 exit(EXIT_SUCCESS);
         }
+
+        /* Test for accessible device file */
+        if (access(option.tty_device, R_OK) == 0)
+            return;
     }
 }
 
@@ -139,18 +151,24 @@ int connect_tty(void)
     fd_set rdfs;           /* Read file descriptor set */
     int    maxfd;          /* Maximum file descriptor used */
     static bool first = true;
-    int    status;
     char   c_tty;
     char   c_stdin[3];
+    int    status;
 
     /* Open tty device */
     fd = open(option.tty_device, O_RDWR | O_NOCTTY );
     if (fd < 0)
-        return EXIT_FAILURE;
+    {
+        error = strerror(errno);
+        goto error_open;
+    }
 
     /* Make sure device is of tty type */
     if (!isatty(fd))
-        return EXIT_FAILURE;
+    {
+        error = "Not a tty device";
+        goto error_isatty;
+    }
 
     /* Flush stale I/O data (if any) */
     tcflush(fd, TCIOFLUSH);
@@ -164,7 +182,7 @@ int connect_tty(void)
 
     /* Save current port settings */
     if (tcgetattr(fd, &old_tio) < 0)
-        return EXIT_FAILURE;
+        goto error_tcgetattr;
 
     /* Make sure we restore tty settings on exit */
     if (first)
@@ -216,13 +234,16 @@ int connect_tty(void)
             {
                 /* Error reading - device is likely unplugged */
                 disconnect_tty();
-                return EXIT_FAILURE;
+                goto error_reading;
             }
         }
         if (FD_ISSET(STDIN_FILENO, &rdfs))
         {
             /* Input from stdin ready */
             status = read(STDIN_FILENO, &c_stdin[0], 1);
+            if (status < 0)
+                printf("Warning: Could not read from stdin");
+
             if ((c_stdin[0] != KEY_Q) && (c_stdin[0] != KEY_CTRL_T))
                 tainted = true;
 
@@ -234,6 +255,8 @@ int connect_tty(void)
 
             /* Forward input to tty device */
             status = write(fd, &c_stdin[0], 1);
+            if (status < 0)
+                printf("Warning: Could not write to tty device");
 
             /* Write to log */
             if (option.log)
@@ -245,5 +268,13 @@ int connect_tty(void)
         }
     }
 
-    return EXIT_SUCCESS;
+    return TIO_SUCCESS;
+
+error_tcgetattr:
+error_isatty:
+    close(fd);
+    connected = false;
+error_reading:
+error_open:
+    return TIO_ERROR;
 }