another attempt to workaround a glibc bug

This is another attempt to fix issue #3644 that we believe is due to issue
https://sourceware.org/bugzilla/show_bug.cgi?id=20632.

src/common.cpp

@@ -1710,7 +1710,9 @@ void restore_term_foreground_process_group(void) {
     if (initial_fg_process_group != -1) {
         // This is called during shutdown and from a signal handler. We don't bother to complain on
         // failure.
-        tcsetpgrp(STDIN_FILENO, initial_fg_process_group);
+        if (tcsetpgrp(STDIN_FILENO, initial_fg_process_group) == -1 && errno == ENOTTY) {
+            redirect_tty_output();
+        }
     }
 }
 
@@ -1943,13 +1945,13 @@ bool fish_reserved_codepoint(wchar_t c) {
            (c >= INPUT_COMMON_BASE && c < INPUT_COMMON_END);
 }
 
-/// Reopen stdout and/or stderr on /dev/null. This is invoked when we find that our tty has become
+/// Reopen stdin, stdout and/or stderr on /dev/null. This is invoked when we find that our tty has
-/// invalid.
+/// become invalid.
 void redirect_tty_output() {
     struct termios t;
     int fd = open("/dev/null", O_WRONLY);
-    if (tcgetattr(STDIN_FILENO, &t) == -1) dup2(fd, STDIN_FILENO);
+    if (tcgetattr(STDIN_FILENO, &t) == -1 && errno == EIO) dup2(fd, STDIN_FILENO);
-    if (tcgetattr(STDOUT_FILENO, &t) == -1) dup2(fd, STDOUT_FILENO);
+    if (tcgetattr(STDOUT_FILENO, &t) == -1 && errno == EIO) dup2(fd, STDOUT_FILENO);
-    if (tcgetattr(STDERR_FILENO, &t) == -1) dup2(fd, STDERR_FILENO);
+    if (tcgetattr(STDERR_FILENO, &t) == -1 && errno == EIO) dup2(fd, STDERR_FILENO);
     close(fd);
 }

src/proc.cpp

@@ -820,7 +820,7 @@ static int terminal_return_from_job(job_t *j) {
 
     // Save jobs terminal modes.
     if (tcgetattr(STDIN_FILENO, &j->tmodes)) {
-        if (errno == ENOTTY) redirect_tty_output();
+        if (errno == EIO) redirect_tty_output();
         debug(1, _(L"Could not return shell to foreground"));
         wperror(L"tcgetattr");
         return 0;
@@ -832,7 +832,8 @@ static int terminal_return_from_job(job_t *j) {
 // https://github.com/fish-shell/fish-shell/issues/121
 #if 0
     // Restore the shell's terminal modes.
-    if (tcsetattr(STDIN_FILENO, TCSADRAIN, &shell_modes)) {
+    if (tcsetattr(STDIN_FILENO, TCSADRAIN, &shell_modes) == -1) {
+        if (errno == EIO) redirect_tty_output();
         debug(1, _(L"Could not return shell to foreground"));
         wperror(L"tcsetattr");
         return 0;

src/reader.cpp

@@ -318,7 +318,7 @@ static void term_donate() {
 
     while (1) {
         if (tcsetattr(STDIN_FILENO, TCSANOW, &tty_modes_for_external_cmds) == -1) {
-            if (errno == ENOTTY) redirect_tty_output();
+            if (errno == EIO) redirect_tty_output();
             if (errno != EINTR) {
                 debug(1, _(L"Could not set terminal mode for new job"));
                 wperror(L"tcsetattr");
@@ -347,7 +347,7 @@ static void update_buff_pos(editable_line_t *el, size_t buff_pos) {
 static void term_steal() {
     while (1) {
         if (tcsetattr(STDIN_FILENO, TCSANOW, &shell_modes) == -1) {
-            if (errno == ENOTTY) redirect_tty_output();
+            if (errno == EIO) redirect_tty_output();
             if (errno != EINTR) {
                 debug(1, _(L"Could not set terminal mode for shell"));
                 perror("tcsetattr");
@@ -794,7 +794,7 @@ void restore_term_mode() {
     // Restore the term mode if we own the terminal. It's important we do this before
     // restore_foreground_process_group, otherwise we won't think we own the terminal.
     if (getpid() == tcgetpgrp(STDIN_FILENO)) {
-        if (tcsetattr(STDIN_FILENO, TCSANOW, &terminal_mode_on_startup) == -1 && errno == ENOTTY) {
+        if (tcsetattr(STDIN_FILENO, TCSANOW, &terminal_mode_on_startup) == -1 && errno == EIO) {
             redirect_tty_output();
         }
     }
@@ -1590,8 +1590,9 @@ static void reader_interactive_init() {
         for (unsigned long loop_count = 0;; loop_count++) {
             pid_t owner = tcgetpgrp(STDIN_FILENO);
             shell_pgid = getpgrp();
-            if (owner < 0 && errno == ENOTTY) {
+            if (owner == -1 && errno == ENOTTY) {
                 // No TTY, cannot be interactive?
+                redirect_tty_output();
                 debug(1, _(L"No TTY for interactive shell (tcgetpgrp failed)"));
                 wperror(L"setpgid");
                 exit_without_destructors(1);
@@ -1643,7 +1644,7 @@ static void reader_interactive_init() {
 
     // Set the new modes.
     if (tcsetattr(0, TCSANOW, &shell_modes) == -1) {
-        if (errno == ENOTTY) redirect_tty_output();
+        if (errno == EIO) redirect_tty_output();
         wperror(L"tcsetattr");
     }
 
@@ -2383,10 +2384,10 @@ const wchar_t *reader_readline(int nchars) {
     reader_repaint();
 
     // Get the current terminal modes. These will be restored when the function returns.
-    tcgetattr(STDIN_FILENO, &old_modes);
+    if (tcgetattr(STDIN_FILENO, &old_modes) == -1 && errno == EIO) redirect_tty_output();
     // Set the new modes.
     if (tcsetattr(0, TCSANOW, &shell_modes) == -1) {
-        if (errno == ENOTTY) redirect_tty_output();
+        if (errno == EIO) redirect_tty_output();
         wperror(L"tcsetattr");
     }
 
@@ -3253,7 +3254,7 @@ const wchar_t *reader_readline(int nchars) {
 
     if (!reader_exit_forced()) {
         if (tcsetattr(0, TCSANOW, &old_modes) == -1) {
-            if (errno == ENOTTY) redirect_tty_output();
+            if (errno == EIO) redirect_tty_output();
             wperror(L"tcsetattr");  // return to previous mode
         }
         set_color(rgb_color_t::reset(), rgb_color_t::reset());
@@ -3359,7 +3360,20 @@ int reader_read(int fd, const io_chain_t &io) {
     // If reader_read is called recursively through the '.' builtin, we need to preserve
     // is_interactive. This, and signal handler setup is handled by
     // proc_push_interactive/proc_pop_interactive.
-    int inter = ((fd == STDIN_FILENO) && isatty(STDIN_FILENO));
+    int inter = 0;
+    // This block is a hack to work around https://sourceware.org/bugzilla/show_bug.cgi?id=20632.
+    // See also, commit 396bf12. Without the need for this workaround we would just write:
+    // int inter = ((fd == STDIN_FILENO) && isatty(STDIN_FILENO));
+    if (fd == STDIN_FILENO) {
+        struct termios t;
+        int a_tty = isatty(STDIN_FILENO);
+        if (a_tty) {
+            inter = 1;
+        } else if (tcgetattr(STDIN_FILENO, &t) == -1 && errno == EIO) {
+            redirect_tty_output();
+            inter = 1;
+        }
+    }
     proc_push_interactive(inter);
 
     res = shell_is_interactive() ? read_i() : read_ni(fd, io);