Ticket #5056: avoid subshell warning for mcedit run from mc.

Don't show message "GNU Midnight Commander is already running on this
terminal. Subshell support will be disabled." if standalone
mcedit/mcview/mcdiffview is run from mc. Show this message only in case
of mc run from another mc, as was before commit
41abcbf706 (ticket #3380).

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

lib/global.c

@@ -50,6 +50,7 @@
 /* *INDENT-OFF* */
 mc_global_t mc_global = {
     .mc_run_mode = MC_RUN_FULL,
+    .run_from_parent_mc = FALSE,
     .timer = NULL,
     .midnight_shutdown = FALSE,
 

lib/global.h

@@ -166,6 +166,7 @@ typedef enum
 typedef struct
 {
     mc_run_mode_t mc_run_mode;
+    gboolean run_from_parent_mc;
     /* global timer */
     mc_timer_t *timer;
     /* Used so that widgets know if they are being destroyed or shut down */

src/main.c

@@ -38,8 +38,10 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
+#include <unistd.h>             /* getsid() */
 
 #include "lib/global.h"
 
@@ -210,6 +212,35 @@ init_sigchld (void)
     }
 }
 
+/* --------------------------------------------------------------------------------------------- */
+/**
+ * Check MC_SID to prevent running one mc from another.
+ *
+ * @return TRUE if no parent mc in our session was found, FALSE otherwise.
+ */
+
+static gboolean
+check_sid (void)
+{
+    pid_t my_sid, old_sid;
+    const char *sid_str;
+
+    sid_str = getenv ("MC_SID");
+    if (sid_str == NULL)
+        return TRUE;
+
+    old_sid = (pid_t) strtol (sid_str, NULL, 0);
+    if (old_sid == 0)
+        return TRUE;
+
+    my_sid = getsid (0);
+    if (my_sid == -1)
+        return TRUE;
+
+    /* The parent mc is in a different session, it's OK */
+    return (old_sid != my_sid);
+}
+
 /* --------------------------------------------------------------------------------------------- */
 /*** public functions ****************************************************************************/
 /* --------------------------------------------------------------------------------------------- */
@@ -222,6 +253,8 @@ main (int argc, char *argv[])
     char *config_migrate_msg = NULL;
     int exit_code = EXIT_FAILURE;
 
+    mc_global.run_from_parent_mc = !check_sid ();
+
     mc_global.timer = mc_timer_new ();
 
     /* We had LC_CTYPE before, LC_ALL includs LC_TYPE as well */
@@ -331,6 +364,10 @@ main (int argc, char *argv[])
     handle_console (CONSOLE_INIT);
 
 #ifdef ENABLE_SUBSHELL
+    /* Disallow subshell when invoked as standalone viewer or editor from running mc */
+    if (mc_global.mc_run_mode != MC_RUN_FULL && mc_global.run_from_parent_mc)
+        mc_global.tty.use_subshell = FALSE;
+
     if (mc_global.tty.use_subshell)
         subshell_get_console_attributes ();
 #endif /* ENABLE_SUBSHELL */
@@ -370,32 +407,57 @@ main (int argc, char *argv[])
 #ifdef ENABLE_SUBSHELL
     /* Done here to ensure that the subshell doesn't  */
     /* inherit the file descriptors opened below, etc */
+    if (mc_global.tty.use_subshell && mc_global.run_from_parent_mc)
+    {
+        int r;
+
+        r = query_dialog (_("Warning"),
+                          _("GNU Midnight Commander\nis already running on this terminal.\n"
+                            "Subshell support will be disabled."),
+                          D_ERROR, 2, _("&OK"), _("&Quit"));
+        if (r == 0)
+        {
+            /* parent mc was found and the user wants to continue */
+            ;
+        }
+        else
+        {
+            /* parent mc was found and the user wants to quit mc */
+            mc_global.midnight_shutdown = TRUE;
+        }
+
+        mc_global.tty.use_subshell = FALSE;
+    }
+
     if (mc_global.tty.use_subshell)
         init_subshell ();
 #endif /* ENABLE_SUBSHELL */
 
-    /* Also done after init_subshell, to save any shell init file messages */
+    if (!mc_global.midnight_shutdown)
-    if (mc_global.tty.console_flag != '\0')
-        handle_console (CONSOLE_SAVE);
-
-    if (mc_global.tty.alternate_plus_minus)
-        application_keypad_mode ();
-
-    /* Done after subshell initialization to allow select and paste text by mouse
-       w/o Shift button in subshell in the native console */
-    init_mouse ();
-
-    /* Done after tty_enter_ca_mode (tty_init) because in VTE bracketed mode is
-       separate for the normal and alternate screens */
-    enable_bracketed_paste ();
-
-    /* subshell_prompt is NULL here */
-    mc_prompt = (geteuid () == 0) ? "# " : "$ ";
-
-    if (config_migrated)
     {
-        message (D_ERROR, _("Warning"), "%s", config_migrate_msg);
+        /* Also done after init_subshell, to save any shell init file messages */
-        g_free (config_migrate_msg);
+        if (mc_global.tty.console_flag != '\0')
+            handle_console (CONSOLE_SAVE);
+
+        if (mc_global.tty.alternate_plus_minus)
+            application_keypad_mode ();
+
+        /* Done after subshell initialization to allow select and paste text by mouse
+           w/o Shift button in subshell in the native console */
+        init_mouse ();
+
+        /* Done after tty_enter_ca_mode (tty_init) because in VTE bracketed mode is
+           separate for the normal and alternate screens */
+        enable_bracketed_paste ();
+
+        /* subshell_prompt is NULL here */
+        mc_prompt = (geteuid () == 0) ? "# " : "$ ";
+
+        if (config_migrated)
+        {
+            message (D_ERROR, _("Warning"), "%s", config_migrate_msg);
+            g_free (config_migrate_msg);
+        }
     }
 
     /* Program main loop */

src/subshell/common.c

@@ -402,47 +402,6 @@ init_subshell_child (const char *pty_name)
     my_exit (FORK_FAILURE);
 }
 
-
-/* --------------------------------------------------------------------------------------------- */
-/**
- * Check MC_SID to prevent running one mc from another.
- * Return:
- * 0 if no parent mc in our session was found,
- * 1 if parent mc was found and the user wants to continue,
- * 2 if parent mc was found and the user wants to quit mc.
- */
-
-static int
-check_sid (void)
-{
-    pid_t my_sid, old_sid;
-    const char *sid_str;
-    int r;
-
-    sid_str = getenv ("MC_SID");
-    if (sid_str == NULL)
-        return 0;
-
-    old_sid = (pid_t) strtol (sid_str, NULL, 0);
-    if (old_sid == 0)
-        return 0;
-
-    my_sid = getsid (0);
-    if (my_sid == -1)
-        return 0;
-
-    /* The parent mc is in a different session, it's OK */
-    if (old_sid != my_sid)
-        return 0;
-
-    r = query_dialog (_("Warning"),
-                      _("GNU Midnight Commander is already\n"
-                        "running on this terminal.\n"
-                        "Subshell support will be disabled."), D_ERROR, 2, _("&OK"), _("&Quit"));
-
-    return (r != 0) ? 2 : 1;
-}
-
 /* --------------------------------------------------------------------------------------------- */
 
 static void
@@ -1012,19 +971,6 @@ init_subshell (void)
     /* Must be considerably longer than BUF_SMALL (128) to support fancy shell prompts */
     char precmd[BUF_MEDIUM];
 
-    switch (check_sid ())
-    {
-    case 1:
-        mc_global.tty.use_subshell = FALSE;
-        return;
-    case 2:
-        mc_global.tty.use_subshell = FALSE;
-        mc_global.midnight_shutdown = TRUE;
-        return;
-    default:
-        break;
-    }
-
     /* Take the current (hopefully pristine) tty mode and make */
     /* a raw mode based on it now, before we do anything else with it */
     init_raw_mode ();