Make main_ui be heap allocated

This is preparation for being able to create more than one UI object.

The change to gdb_main to stop using catch_errors is necessary because
catch_errors references current_uiout, which expands to
current_ui->m_current_ui, which would crash because current_ui is not
initialized yet at that point.  It didn't trigger earlier in the
series because before this patch, main_ui/current_ui always start out
non-NULL.

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* event-top.c (main_ui_): Delete.
	(main_ui, current_ui, ui_list): No longer initialize here.
	* main.c (captured_main): UI initialization code factored out to
	new new_ui function.
	(gdb_main): Wrap captured_main with TRY/CATCH instead of
	catch_errors.
	* top.c (highest_ui_num): New global.
	(new_ui): New function.
	* top.h (struct ui) <num>: New field.
	(new_ui): New declaration.

gdb/ChangeLog

@@ -1,3 +1,16 @@
+2016-06-21  Pedro Alves  <palves@redhat.com>
+
+	* event-top.c (main_ui_): Delete.
+	(main_ui, current_ui, ui_list): No longer initialize here.
+	* main.c (captured_main): UI initialization code factored out to
+	new new_ui function.
+	(gdb_main): Wrap captured_main with TRY/CATCH instead of
+	catch_errors.
+	* top.c (highest_ui_num): New global.
+	(new_ui): New function.
+	* top.h (struct ui) <num>: New field.
+	(new_ui): New declaration.
+
 2016-06-21  Pedro Alves  <palves@redhat.com>
 
 	* cli/cli-interp.c (cli_on_normal_stop): Bail out early if there's

gdb/event-top.c

@@ -441,12 +441,11 @@ top_level_prompt (void)
   return xstrdup (prompt);
 }
 
-/* The main UI.  */
-static struct ui main_ui_;
+/* See top.h.  */
 
-struct ui *main_ui = &main_ui_;
-struct ui *current_ui = &main_ui_;
-struct ui *ui_list = &main_ui_;
+struct ui *main_ui;
+struct ui *current_ui;
+struct ui *ui_list;
 
 /* See top.h.  */
 

gdb/main.c

@@ -443,7 +443,6 @@ DEF_VEC_O (cmdarg_s);
 static int
 captured_main (void *data)
 {
-  struct ui *ui = current_ui;
   struct captured_main_args *context = (struct captured_main_args *) data;
   int argc = context->argc;
   char **argv = context->argv;
@@ -514,26 +513,15 @@ captured_main (void *data)
 
   saved_command_line = (char *) xstrdup ("");
 
-  ui->instream = stdin;
-  ui->outstream = stdout;
-  ui->errstream = stderr;
-
-  ui->input_fd = fileno (stdin);
-
-  ui->prompt_state = PROMPT_NEEDED;
-
 #ifdef __MINGW32__
   /* Ensure stderr is unbuffered.  A Cygwin pty or pipe is implemented
      as a Windows pipe, and Windows buffers on pipes.  */
   setvbuf (stderr, NULL, _IONBF, BUFSIZ);
 #endif
 
-  gdb_stdout = stdio_fileopen (stdout);
-  gdb_stderr = stderr_fileopen (stderr);
+  main_ui = new_ui (stdin, stdout, stderr);
+  current_ui = main_ui;
 
-  gdb_stdlog = gdb_stderr;	/* for moment */
-  gdb_stdtarg = gdb_stderr;	/* for moment */
-  gdb_stdin = stdio_fileopen (stdin);
   gdb_stdtargerr = gdb_stderr;	/* for moment */
   gdb_stdtargin = gdb_stdin;	/* for moment */
 
@@ -1174,7 +1162,16 @@ captured_main (void *data)
 int
 gdb_main (struct captured_main_args *args)
 {
-  catch_errors (captured_main, args, "", RETURN_MASK_ALL);
+  TRY
+    {
+      captured_main (args);
+    }
+  CATCH (ex, RETURN_MASK_ALL)
+    {
+      exception_print (gdb_stderr, ex);
+    }
+  END_CATCH
+
   /* The only way to end up here is by an error (normal exit is
      handled by quit_force()), hence always return an error status.  */
   return 1;

gdb/top.c

@@ -246,6 +246,46 @@ void (*deprecated_call_command_hook) (struct cmd_list_element * c,
 
 void (*deprecated_context_hook) (int id);
 
+/* The highest UI number ever assigned.  */
+static int highest_ui_num;
+
+/* See top.h.  */
+
+struct ui *
+new_ui (FILE *instream, FILE *outstream, FILE *errstream)
+{
+  struct ui *ui;
+
+  ui = XCNEW (struct ui);
+
+  ui->num = ++highest_ui_num;
+  ui->instream = instream;
+  ui->outstream = outstream;
+  ui->errstream = errstream;
+
+  ui->input_fd = fileno (ui->instream);
+
+  ui->m_gdb_stdin = stdio_fileopen (ui->instream);
+  ui->m_gdb_stdout = stdio_fileopen (ui->outstream);
+  ui->m_gdb_stderr = stderr_fileopen (ui->errstream);
+  ui->m_gdb_stdlog = ui->m_gdb_stderr;
+
+  ui->prompt_state = PROMPT_NEEDED;
+
+  if (ui_list == NULL)
+    ui_list = ui;
+  else
+    {
+      struct ui *last;
+
+      for (last = ui_list; last->next != NULL; last = last->next)
+	;
+      last->next = ui;
+    }
+
+  return ui;
+}
+
 /* Handler for SIGHUP.  */
 
 #ifdef SIGHUP

gdb/top.h

@@ -57,6 +57,9 @@ struct ui
   /* Pointer to next in singly-linked list.  */
   struct ui *next;
 
+  /* Convenient handle (UI number).  Unique across all UIs.  */
+  int num;
+
   /* The UI's command line buffer.  This is to used to accumulate
      input until we have a whole command line.  */
   struct buffer line_buffer;
@@ -170,6 +173,9 @@ extern void switch_thru_all_uis_next (struct switch_thru_all_uis *state);
 #define ALL_UIS(UI)				\
   for (UI = ui_list; UI; UI = UI->next)		\
 
+/* Create a new UI.  */
+extern struct ui *new_ui (FILE *instream, FILE *outstream, FILE *errstream);
+
 /* Cleanup that restores the current UI.  */
 extern void restore_ui_cleanup (void *data);