GTK: fixed --detach and support stdout/stderr redirections

* We fork after command line arguments have been parsed, which
  is after gtk_get_option_group() has been called.
  This means that GTK was already initialized and it wasn't safe
  to continue after forking.
* As a workaround, we now re-exec with the original argv array,
  so GTK can be properly reinitialized.
  Since we did not remove `--detach` from argv (and that would be
  nontrivial), it would fork again endlessly,
  so we use an environment variable
  $__SCITECO_DETACHED to guard against recursive forks.
* Also, do not close stdin/stdout/stderr if has been redirected
  to a file, so you can now e.g. call `gsciteco -d >some-file`.
* This was broken since v2.5.0.

4 files changed, 29 insertions, 8 deletions

diff --git a/src/interface-curses/interface.c b/src/interface-curses/interface.c
index 6c8b231..365a096 100644
--- a/src/interface-curses/interface.c
+++ b/src/interface-curses/interface.c
@@ -443,7 +443,7 @@ static void teco_interface_set_window_title(const gchar *title);
 static void teco_interface_draw_info(void);
 
 void
-teco_interface_init(void)
+teco_interface_init(gint argc, gchar **argv)
 {
 	for (guint i = 0; i < G_N_ELEMENTS(teco_interface.color_table); i++)
 		teco_interface.color_table[i] = -1;
diff --git a/src/interface-gtk/interface.c b/src/interface-gtk/interface.c
index ace3a2f..08ccf5d 100644
--- a/src/interface-gtk/interface.c
+++ b/src/interface-gtk/interface.c
@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <signal.h>
+#include <unistd.h>
 
 #include <glib.h>
 #include <glib/gprintf.h>
@@ -132,10 +133,10 @@ static struct {
 } teco_interface;
 
 void
-teco_interface_init(void)
+teco_interface_init(gint argc, gchar **argv)
 {
 #ifdef G_OS_UNIX
-	if (teco_interface.detach) {
+	if (teco_interface.detach && !g_getenv("__SCITECO_DETACHED")) {
 		/*
 		 * NOTE: There is also daemon() on BSD/Linux,
 		 * but the following should be more portable.
@@ -148,9 +149,29 @@ teco_interface_init(void)
 
 		setsid();
 
-		g_freopen("/dev/null", "r", stdin);
-		g_freopen("/dev/null", "a+", stdout);
-		g_freopen("/dev/null", "a+", stderr);
+		if (isatty(0)) {
+			G_GNUC_UNUSED FILE *stdin_new = g_freopen("/dev/null", "r", stdin);
+			g_assert(stdin_new != NULL);
+		}
+		if (isatty(1)) {
+			G_GNUC_UNUSED FILE *stdout_new = g_freopen("/dev/null", "a+", stdout);
+			g_assert(stdout_new != NULL);
+		}
+		if (isatty(2)) {
+			G_GNUC_UNUSED FILE *stderr_new = g_freopen("/dev/null", "a+", stderr);
+			g_assert(stderr_new != NULL);
+		}
+
+		/*
+		 * gtk_get_option_group() already initialized GTK and even though the
+		 * display is not yet opened, it's unsafe to continue.
+		 * Instead, we re-exec already in the child process.
+		 * We cannot easily remove --detach from argv, but still guard against
+		 * recursive forks by using an environment variable.
+		 */
+		g_setenv("__SCITECO_DETACHED", "1", TRUE);
+		execv(argv[0], argv);
+		g_assert_not_reached();
 	}
 #endif
 
diff --git a/src/interface.h b/src/interface.h
index f196a83..54f807b 100644
--- a/src/interface.h
+++ b/src/interface.h
@@ -51,7 +51,7 @@
 extern teco_view_t *teco_interface_current_view;
 
 /** @pure */
-void teco_interface_init(void);
+void teco_interface_init(gint argc, gchar **argv);
 
 /** @pure */
 GOptionGroup *teco_interface_get_options(void);
diff --git a/src/main.c b/src/main.c
index 4d46817..0023c78 100644
--- a/src/main.c
+++ b/src/main.c
@@ -445,7 +445,7 @@ main(int argc, char **argv)
 	 */
 	teco_qreg_table_init(&teco_qreg_table_globals, TRUE);
 
-	teco_interface_init();
+	teco_interface_init(argc, argv);
 
 	/*
 	 * QRegister view must be initialized only now