Make gdb_stdout&co be per UI

We need to have these send output to the proper UI.

However, this patch still make them look like globals.  Kind of like
__thread variables, if you will.  Changing everything throughout to
write something like current_ui->gdb_stdout instead would be massive
overkill, IMNSHO.

This leaves gdb_stdtargin/stdtarg/stdtargerr global, but maybe that was a
mistake, I'm not sure -- IIRC, MI formats target I/O differently, so
if we have a separate MI channel, then I guess target output should go
there instead of to gdb's stdout.  OTOH, maybe GDB should send that
instead to "set inferior-tty", instead of multiplexing it over MI.  We
can always fix those later when it gets clearer where they should go.

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

	* main.c (gdb_stdout, gdb_stderr, gdb_stdlog, gdb_stdin): Delete
	globals.
	(gen_ret_current_ui_field_ptr): New macro.  Use it to generate
	wrappers for gdb_stdout, gdb_stderr, gdb_stdlog and gdb_stdin.
	* top.h (struct ui) <m_gdb_stdout, m_gdb_stdin, m_gdb_stderr,
	m_gdb_stdlog>: New fields.
	(current_ui_gdb_stdout_ptr, current_ui_gdb_stdin_ptr)
	(current_ui_gdb_stderr_ptr, current_ui_gdb_stdlog_ptr): Declare.
	(gdb_stdout, gdb_stdin, gdb_stderr, gdb_stdlog): Reimplement as
	macros.

gdb/ChangeLog

@@ -1,3 +1,16 @@
+2016-06-21  Pedro Alves  <palves@redhat.com>
+
+	* main.c (gdb_stdout, gdb_stderr, gdb_stdlog, gdb_stdin): Delete
+	globals.
+	(gen_ret_current_ui_field_ptr): New macro.  Use it to generate
+	wrappers for gdb_stdout, gdb_stderr, gdb_stdlog and gdb_stdin.
+	* top.h (struct ui) <m_gdb_stdout, m_gdb_stdin, m_gdb_stderr,
+	m_gdb_stdlog>: New fields.
+	(current_ui_gdb_stdout_ptr, current_ui_gdb_stdin_ptr)
+	(current_ui_gdb_stderr_ptr, current_ui_gdb_stdlog_ptr): Declare.
+	(gdb_stdout, gdb_stdin, gdb_stderr, gdb_stdlog): Reimplement as
+	macros.
+
 2016-06-21  Pedro Alves  <palves@redhat.com>
 
 	* event-top.c: Update readline-related comments.

gdb/main.c

@@ -68,10 +68,6 @@ static int gdb_datadir_provided = 0;
    the possibly relocated path to python's lib directory.  */
 char *python_libdir = 0;
 
-struct ui_file *gdb_stdout;
-struct ui_file *gdb_stderr;
-struct ui_file *gdb_stdlog;
-struct ui_file *gdb_stdin;
 /* Target IO streams.  */
 struct ui_file *gdb_stdtargin;
 struct ui_file *gdb_stdtarg;

gdb/top.c

@@ -86,6 +86,21 @@ extern void initialize_all_files (void);
 #define DEFAULT_PROMPT	"(gdb) "
 #endif
 
+/* Generate a function that exports a pointer to a field of the
+   current UI.  */
+
+#define gen_ret_current_ui_field_ptr(type, name)	\
+type *							\
+current_ui_## name ## _ptr (void)			\
+{							\
+  return &current_ui->m_ ## name;		\
+}
+
+gen_ret_current_ui_field_ptr (struct ui_file *, gdb_stdout)
+gen_ret_current_ui_field_ptr (struct ui_file *, gdb_stdin)
+gen_ret_current_ui_field_ptr (struct ui_file *, gdb_stderr)
+gen_ret_current_ui_field_ptr (struct ui_file *, gdb_stdlog)
+
 /* Initialization file name for gdb.  This is host-dependent.  */
 
 const char gdbinit[] = GDBINIT;

gdb/top.h

@@ -49,6 +49,23 @@ struct ui
   /* The function to invoke when a complete line of input is ready for
      processing.  */
   void (*input_handler) (char *);
+
+  /* The fields below that start with "m_" are "private".  They're
+     meant to be accessed through wrapper macros that make them look
+     like globals.  */
+
+  /* The ui_file streams.  */
+  /* Normal results */
+  struct ui_file *m_gdb_stdout;
+  /* Input stream */
+  struct ui_file *m_gdb_stdin;
+  /* Serious error notifications */
+  struct ui_file *m_gdb_stderr;
+  /* Log/debug/trace messages that should bypass normal stdout/stderr
+     filtering.  For moment, always call this stream using
+     *_unfiltered.  In the very near future that restriction shall be
+     removed - either call shall be unfiltered.  (cagney 1999-06-13).  */
+  struct ui_file *m_gdb_stdlog;
 };
 
 extern struct ui *current_ui;

gdb/utils.h

@@ -159,18 +159,27 @@ extern void reinitialize_more_filter (void);
 
 extern int pagination_enabled;
 
-/* Global ui_file streams.  These are all defined in main.c.  */
+extern struct ui_file **current_ui_gdb_stdout_ptr (void);
+extern struct ui_file **current_ui_gdb_stdin_ptr (void);
+extern struct ui_file **current_ui_gdb_stderr_ptr (void);
+extern struct ui_file **current_ui_gdb_stdlog_ptr (void);
+
+/* The current top level's ui_file streams.  */
+
 /* Normal results */
-extern struct ui_file *gdb_stdout;
+#define gdb_stdout (*current_ui_gdb_stdout_ptr ())
 /* Input stream */
-extern struct ui_file *gdb_stdin;
+#define gdb_stdin (*current_ui_gdb_stdin_ptr ())
 /* Serious error notifications */
-extern struct ui_file *gdb_stderr;
+#define gdb_stderr (*current_ui_gdb_stderr_ptr ())
 /* Log/debug/trace messages that should bypass normal stdout/stderr
    filtering.  For moment, always call this stream using
    *_unfiltered.  In the very near future that restriction shall be
    removed - either call shall be unfiltered.  (cagney 1999-06-13).  */
-extern struct ui_file *gdb_stdlog;
+#define gdb_stdlog (*current_ui_gdb_stdlog_ptr ())
+
+/* Truly global ui_file streams.  These are all defined in main.c.  */
+
 /* Target output that should bypass normal stdout/stderr filtering.
    For moment, always call this stream using *_unfiltered.  In the
    very near future that restriction shall be removed - either call