Change the pager to a ui_file

This rewrites the output pager as a ui_file implementation.

A new header is introduced to declare the pager class.  The
implementation remains in utils.c for the time being, because there
are some static globals there that must be used by this code.  (This
could be cleaned up at some future date.)

I went through all the text output in gdb to ensure that this change
should be ok.  There are a few cases:

* Any existing call to printf_unfiltered is required to be avoid the
  pager.  This is ensured directly in the implementation.

* All remaining calls to the f*_unfiltered functions -- the ones that
  take an explicit ui_file -- either send to an unfiltered stream
  (e.g., gdb_stderr), which is obviously ok; or conditionally send to
  gdb_stdout

  I investigated all such calls by searching for:

    grep -e '\bf[a-z0-9_]*_unfiltered' *.[chyl] */*.[ch] | grep -v gdb_stdlog | grep -v gdb_stderr

  This yields a number of candidates to check.

  * The breakpoint _print_recreate family, and
    save_trace_state_variables.  These are used for "save" commands
    and so are fine.

  * Things printing to a temporary stream.  Obviously ok.

  * Disassembly selftests.

  * print_gdb_help - this is non-obvious, but ok because paging isn't
    yet enabled at this point during startup.

  * serial.c - doens't use gdb_stdout

  * The code in compile/.  This is all printing to a file.

  * DWARF DIE dumping - doesn't reference gdb_stdout.

* Calls to the _filtered form -- these are all clearly ok, because if
  they are using gdb_stdout, then filtering will still apply; and if
  not, then filtering never applied and still will not.

Therefore, at this point, there is no longer any distinction between
all the other _filtered and _unfiltered calls, and they can be
unified.

In this patch, take special note of the vfprintf_maybe_filtered and
ui_file::vprintf change.  This is one instance of the above idea,
erasing the distinction between filtered and unfiltered -- in this
part of the change, the "unfiltered_output" flag is never passe to
cli_ui_out.  Subsequent patches will go much further in this
direction.

Also note the can_emit_style_escape changes in ui-file.c.  Checking
against gdb_stdout or gdb_stderr was always a bit of a hack; and now
it is no longer needed, because this is decision can be more fully
delegated to the particular ui_file implementation.

ui_file::can_page is removed, because this patch removed the only call
to it.

I think this is the main part of fixing PR cli/7234.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=7234

1 files changed, 96 insertions, 160 deletions

diff --git a/gdb/utils.c b/gdb/utils.c
index 57ce9ca..70b2660 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -77,6 +77,7 @@
 #include "gdbsupport/gdb-safe-ctype.h"
 #include "bt-utils.h"
 #include "gdbsupport/buildargv.h"
+#include "pager.h"
 
 void (*deprecated_error_begin_hook) (void);
 
@@ -86,10 +87,6 @@ static void vfprintf_maybe_filtered (struct ui_file *, const char *,
 				     va_list, bool)
   ATTRIBUTE_PRINTF (2, 0);
 
-static void fputs_maybe_filtered (const char *, struct ui_file *, int);
-
-static void prompt_for_continue (void);
-
 static void set_screen_size (void);
 static void set_width (void);
 
@@ -1171,19 +1168,6 @@ static bool pagination_disabled_for_command;
 
 static bool filter_initialized = false;
 
-/* Contains characters which are waiting to be output (they have
-   already been counted in chars_printed).  */
-static std::string wrap_buffer;
-
-/* String to indent by if the wrap occurs.  */
-static int wrap_indent;
-
-/* Column number on the screen where wrap_buffer begins, or 0 if wrapping
-   is not in effect.  */
-static int wrap_column;
-
-/* The style applied at the time that wrap_here was called.  */
-static ui_file_style wrap_style;
 
 
 /* Initialize the number of lines per page and chars per line.  */
@@ -1315,7 +1299,6 @@ set_width (void)
   if (chars_per_line == 0)
     init_page_info ();
 
-  wrap_buffer.clear ();
   filter_initialized = true;
 }
 
@@ -1344,55 +1327,28 @@ set_screen_width_and_height (int width, int height)
   set_width ();
 }
 
-/* The currently applied style.  */
-
-static ui_file_style applied_style;
-
-/* Emit an ANSI style escape for STYLE.  If STREAM is nullptr, emit to
-   the wrap buffer; otherwise emit to STREAM.  */
-
-static void
-emit_style_escape (const ui_file_style &style,
-		   struct ui_file *stream = nullptr)
+void
+pager_file::emit_style_escape (const ui_file_style &style)
 {
-  if (applied_style != style)
+  if (can_emit_style_escape () && style != m_applied_style)
     {
-      applied_style = style;
-
-      if (stream == nullptr)
-	wrap_buffer.append (style.to_ansi ());
+      m_applied_style = style;
+      if (m_paging)
+	m_stream->emit_style_escape (style);
       else
-	stream->puts (style.to_ansi ().c_str ());
+	m_wrap_buffer.append (style.to_ansi ());
     }
 }
 
-/* Set the current output style.  This will affect future uses of the
-   _filtered output functions.  */
-
-static void
-set_output_style (struct ui_file *stream, const ui_file_style &style)
-{
-  if (!stream->can_emit_style_escape ())
-    return;
-
-  /* Note that we may not pass STREAM here, when we want to emit to
-     the wrap buffer, not directly to STREAM.  */
-  if (stream == gdb_stdout)
-    stream = nullptr;
-  emit_style_escape (style, stream);
-}
-
-/* See utils.h.  */
+/* See pager.h.  */
 
 void
-reset_terminal_style (struct ui_file *stream)
+pager_file::reset_style ()
 {
-  if (stream->can_emit_style_escape ())
+  if (can_emit_style_escape ())
     {
-      /* Force the setting, regardless of what we think the setting
-	 might already be.  */
-      applied_style = ui_file_style ();
-      wrap_buffer.append (applied_style.to_ansi ());
+      m_applied_style = ui_file_style ();
+      m_wrap_buffer.append (m_applied_style.to_ansi ());
     }
 }
 
@@ -1401,8 +1357,8 @@ reset_terminal_style (struct ui_file *stream)
    telling users what to do in the prompt is more user-friendly than
    expecting them to think of Ctrl-C/SIGINT.  */
 
-static void
-prompt_for_continue (void)
+void
+pager_file::prompt_for_continue ()
 {
   char cont_prompt[120];
   /* Used to add duration we waited for user to respond to
@@ -1411,12 +1367,13 @@ prompt_for_continue (void)
   steady_clock::time_point prompt_started = steady_clock::now ();
   bool disable_pagination = pagination_disabled_for_command;
 
+  scoped_restore save_paging = make_scoped_restore (&m_paging, true);
+
   /* Clear the current styling.  */
-  if (gdb_stdout->can_emit_style_escape ())
-    emit_style_escape (ui_file_style (), gdb_stdout);
+  m_stream->emit_style_escape (ui_file_style ());
 
   if (annotation_level > 1)
-    printf_unfiltered (("\n\032\032pre-prompt-for-continue\n"));
+    m_stream->puts (("\n\032\032pre-prompt-for-continue\n"));
 
   strcpy (cont_prompt,
 	  "--Type <RET> for more, q to quit, "
@@ -1439,7 +1396,7 @@ prompt_for_continue (void)
   prompt_for_continue_wait_time += steady_clock::now () - prompt_started;
 
   if (annotation_level > 1)
-    printf_unfiltered (("\n\032\032post-prompt-for-continue\n"));
+    m_stream->puts (("\n\032\032post-prompt-for-continue\n"));
 
   if (ignore != NULL)
     {
@@ -1490,24 +1447,28 @@ reinitialize_more_filter (void)
   pagination_disabled_for_command = false;
 }
 
-/* Flush the wrap buffer to STREAM, if necessary.  */
-
-static void
-flush_wrap_buffer (struct ui_file *stream)
+void
+pager_file::flush_wrap_buffer ()
 {
-  if (stream == gdb_stdout && !wrap_buffer.empty ())
+  if (!m_paging && !m_wrap_buffer.empty ())
     {
-      stream->puts (wrap_buffer.c_str ());
-      wrap_buffer.clear ();
+      m_stream->puts (m_wrap_buffer.c_str ());
+      m_wrap_buffer.clear ();
     }
 }
 
+void
+pager_file::flush ()
+{
+  flush_wrap_buffer ();
+  m_stream->flush ();
+}
+
 /* See utils.h.  */
 
 void
 gdb_flush (struct ui_file *stream)
 {
-  flush_wrap_buffer (stream);
   stream->flush ();
 }
 
@@ -1522,28 +1483,28 @@ get_chars_per_line ()
 /* See ui-file.h.  */
 
 void
-ui_file::wrap_here (int indent)
+pager_file::wrap_here (int indent)
 {
   /* This should have been allocated, but be paranoid anyway.  */
   gdb_assert (filter_initialized);
 
-  flush_wrap_buffer (this);
+  flush_wrap_buffer ();
   if (chars_per_line == UINT_MAX)	/* No line overflow checking.  */
     {
-      wrap_column = 0;
+      m_wrap_column = 0;
     }
   else if (chars_printed >= chars_per_line)
     {
-      puts_filtered ("\n");
+      this->puts ("\n");
       if (indent != 0)
-	puts_filtered (n_spaces (indent));
-      wrap_column = 0;
+	this->puts (n_spaces (indent));
+      m_wrap_column = 0;
     }
   else
     {
-      wrap_column = chars_printed;
-      wrap_indent = indent;
-      wrap_style = applied_style;
+      m_wrap_column = chars_printed;
+      m_wrap_indent = indent;
+      m_wrap_style = m_applied_style;
     }
 }
 
@@ -1606,23 +1567,8 @@ begin_line (void)
     }
 }
 
-
-/* Like fputs but if FILTER is true, pause after every screenful.
-
-   Regardless of FILTER can wrap at points other than the final
-   character of a line.
-
-   Unlike fputs, fputs_maybe_filtered does not return a value.
-   It is OK for LINEBUFFER to be NULL, in which case just don't print
-   anything.
-
-   Note that a longjmp to top level may occur in this routine (only if
-   FILTER is true) (since prompt_for_continue may do so) so this
-   routine should not be called when cleanups are not in place.  */
-
-static void
-fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
-		      int filter)
+void
+pager_file::puts (const char *linebuffer)
 {
   const char *lineptr;
 
@@ -1630,26 +1576,24 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
     return;
 
   /* Don't do any filtering if it is disabled.  */
-  if (!stream->can_page ()
-      || stream != gdb_stdout
-      || !pagination_enabled
+  if (!pagination_enabled
       || pagination_disabled_for_command
       || batch_flag
       || (lines_per_page == UINT_MAX && chars_per_line == UINT_MAX)
       || top_level_interpreter () == NULL
       || top_level_interpreter ()->interp_ui_out ()->is_mi_like_p ())
     {
-      flush_wrap_buffer (stream);
-      stream->puts (linebuffer);
+      flush_wrap_buffer ();
+      m_stream->puts (linebuffer);
       return;
     }
 
   auto buffer_clearer
     = make_scope_exit ([&] ()
 		       {
-			 wrap_buffer.clear ();
-			 wrap_column = 0;
-			 wrap_indent = 0;
+			 m_wrap_buffer.clear ();
+			 m_wrap_column = 0;
+			 m_wrap_indent = 0;
 		       });
 
   /* Go through and output each character.  Show line extension
@@ -1662,7 +1606,7 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
       /* Possible new page.  Note that PAGINATION_DISABLED_FOR_COMMAND
 	 might be set during this loop, so we must continue to check
 	 it here.  */
-      if (filter && (lines_printed >= lines_per_page - 1)
+      if ((lines_printed >= lines_per_page - 1)
 	  && !pagination_disabled_for_command)
 	prompt_for_continue ();
 
@@ -1673,7 +1617,7 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 	  /* Print a single line.  */
 	  if (*lineptr == '\t')
 	    {
-	      wrap_buffer.push_back ('\t');
+	      m_wrap_buffer.push_back ('\t');
 	      /* Shifting right by 3 produces the number of tab stops
 		 we have already passed, and then adding one and
 		 shifting left 3 advances to the next tab stop.  */
@@ -1683,20 +1627,20 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 	  else if (*lineptr == '\033'
 		   && skip_ansi_escape (lineptr, &skip_bytes))
 	    {
-	      wrap_buffer.append (lineptr, skip_bytes);
+	      m_wrap_buffer.append (lineptr, skip_bytes);
 	      /* Note that we don't consider this a character, so we
 		 don't increment chars_printed here.  */
 	      lineptr += skip_bytes;
 	    }
 	  else if (*lineptr == '\r')
 	    {
-	      wrap_buffer.push_back (*lineptr);
+	      m_wrap_buffer.push_back (*lineptr);
 	      chars_printed = 0;
 	      lineptr++;
 	    }
 	  else
 	    {
-	      wrap_buffer.push_back (*lineptr);
+	      m_wrap_buffer.push_back (*lineptr);
 	      chars_printed++;
 	      lineptr++;
 	    }
@@ -1711,12 +1655,12 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 		 prompt is given; and to avoid emitting style
 		 sequences in the middle of a run of text, we track
 		 this as well.  */
-	      ui_file_style save_style = applied_style;
+	      ui_file_style save_style = m_applied_style;
 	      bool did_paginate = false;
 
 	      chars_printed = 0;
 	      lines_printed++;
-	      if (wrap_column)
+	      if (m_wrap_column)
 		{
 		  /* We are about to insert a newline at an historic
 		     location in the WRAP_BUFFER.  Before we do we want to
@@ -1724,28 +1668,21 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 		     need to insert an escape sequence we must restore the
 		     current applied style to how it was at the WRAP_COLUMN
 		     location.  */
-		  applied_style = wrap_style;
-		  if (stream->can_emit_style_escape ())
-		    emit_style_escape (ui_file_style (), stream);
+		  m_applied_style = m_wrap_style;
+		  m_stream->emit_style_escape (ui_file_style ());
 		  /* If we aren't actually wrapping, don't output
 		     newline -- if chars_per_line is right, we
 		     probably just overflowed anyway; if it's wrong,
 		     let us keep going.  */
-		  /* XXX: The ideal thing would be to call
-		     'stream->putc' here, but we can't because it
-		     currently calls 'fputc_unfiltered', which ends up
-		     calling us, which generates an infinite
-		     recursion.  */
-		  stream->puts ("\n");
+		  m_stream->puts ("\n");
 		}
 	      else
-		flush_wrap_buffer (stream);
+		this->flush_wrap_buffer ();
 
 	      /* Possible new page.  Note that
 		 PAGINATION_DISABLED_FOR_COMMAND might be set during
 		 this loop, so we must continue to check it here.  */
-	      if (filter
-		  && lines_printed >= lines_per_page - 1
+	      if (lines_printed >= lines_per_page - 1
 		  && !pagination_disabled_for_command)
 		{
 		  prompt_for_continue ();
@@ -1753,44 +1690,37 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 		}
 
 	      /* Now output indentation and wrapped string.  */
-	      if (wrap_column)
+	      if (m_wrap_column)
 		{
-		  stream->puts (n_spaces (wrap_indent));
+		  m_stream->puts (n_spaces (m_wrap_indent));
 
 		  /* Having finished inserting the wrapping we should
 		     restore the style as it was at the WRAP_COLUMN.  */
-		  if (stream->can_emit_style_escape ())
-		    emit_style_escape (wrap_style, stream);
+		  m_stream->emit_style_escape (m_wrap_style);
 
 		  /* The WRAP_BUFFER will still contain content, and that
 		     content might set some alternative style.  Restore
 		     APPLIED_STYLE as it was before we started wrapping,
 		     this reflects the current style for the last character
 		     in WRAP_BUFFER.  */
-		  applied_style = save_style;
+		  m_applied_style = save_style;
 
 		  /* Note that this can set chars_printed > chars_per_line
 		     if we are printing a long string.  */
-		  chars_printed = wrap_indent + (save_chars - wrap_column);
-		  wrap_column = 0;	/* And disable fancy wrap */
+		  chars_printed = m_wrap_indent + (save_chars - m_wrap_column);
+		  m_wrap_column = 0;	/* And disable fancy wrap */
 		}
-	      else if (did_paginate && stream->can_emit_style_escape ())
-		emit_style_escape (save_style, stream);
+	      else if (did_paginate)
+		m_stream->emit_style_escape (save_style);
 	    }
 	}
 
       if (*lineptr == '\n')
 	{
 	  chars_printed = 0;
-	  stream->wrap_here (0); /* Spit out chars, cancel
-				    further wraps.  */
+	  wrap_here (0); /* Spit out chars, cancel further wraps.  */
 	  lines_printed++;
-	  /* XXX: The ideal thing would be to call
-	     'stream->putc' here, but we can't because it
-	     currently calls 'fputc_unfiltered', which ends up
-	     calling us, which generates an infinite
-	     recursion.  */
-	  stream->puts ("\n");
+	  m_stream->puts ("\n");
 	  lineptr++;
 	}
     }
@@ -1799,15 +1729,24 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 }
 
 void
-fputs_filtered (const char *linebuffer, struct ui_file *stream)
+pager_file::write (const char *buf, long length_buf)
 {
-  fputs_maybe_filtered (linebuffer, stream, 1);
+  /* We have to make a string here because the pager uses
+     skip_ansi_escape, which requires NUL-termination.  */
+  std::string str (buf, length_buf);
+  this->puts (str.c_str ());
 }
 
 void
 fputs_unfiltered (const char *linebuffer, struct ui_file *stream)
 {
-  fputs_maybe_filtered (linebuffer, stream, 0);
+  stream->puts_unfiltered (linebuffer);
+}
+
+void
+fputs_filtered (const char *linebuffer, struct ui_file *stream)
+{
+  stream->puts (linebuffer);
 }
 
 /* See utils.h.  */
@@ -1816,9 +1755,9 @@ void
 fputs_styled (const char *linebuffer, const ui_file_style &style,
 	      struct ui_file *stream)
 {
-  set_output_style (stream, style);
-  fputs_maybe_filtered (linebuffer, stream, 1);
-  set_output_style (stream, ui_file_style ());
+  stream->emit_style_escape (style);
+  fputs_filtered (linebuffer, stream);
+  stream->emit_style_escape (ui_file_style ());
 }
 
 /* See utils.h.  */
@@ -1827,9 +1766,9 @@ void
 fputs_styled_unfiltered (const char *linebuffer, const ui_file_style &style,
 			 struct ui_file *stream)
 {
-  set_output_style (stream, style);
-  fputs_maybe_filtered (linebuffer, stream, 0);
-  set_output_style (stream, ui_file_style ());
+  stream->emit_style_escape (style);
+  stream->puts_unfiltered (linebuffer);
+  stream->emit_style_escape (ui_file_style ());
 }
 
 /* See utils.h.  */
@@ -1853,14 +1792,14 @@ fputs_highlighted (const char *str, const compiled_regex &highlight,
 	}
 
       /* Output pmatch with the highlight style.  */
-      set_output_style (stream, highlight_style.style ());
+      stream->emit_style_escape (highlight_style.style ());
       while (n_highlight > 0)
 	{
 	  fputc_filtered (*str, stream);
 	  n_highlight--;
 	  str++;
 	}
-      set_output_style (stream, ui_file_style ());
+      stream->emit_style_escape (ui_file_style ());
     }
 
   /* Output the trailing part of STR not matching HIGHLIGHT.  */
@@ -1916,10 +1855,7 @@ static void
 vfprintf_maybe_filtered (struct ui_file *stream, const char *format,
 			 va_list args, bool filter)
 {
-  ui_out_flags flags = disallow_ui_out_field;
-  if (!filter)
-    flags |= unfiltered_output;
-  cli_ui_out (stream, flags).vmessage (applied_style, format, args);
+  stream->vprintf (format, args);
 }
 
 
@@ -1975,11 +1911,11 @@ fprintf_styled (struct ui_file *stream, const ui_file_style &style,
 {
   va_list args;
 
-  set_output_style (stream, style);
+  stream->emit_style_escape (style);
   va_start (args, format);
   vfprintf_filtered (stream, format, args);
   va_end (args);
-  set_output_style (stream, ui_file_style ());
+  stream->emit_style_escape (ui_file_style ());
 }
 
 /* See utils.h.  */
@@ -1988,9 +1924,9 @@ void
 vfprintf_styled (struct ui_file *stream, const ui_file_style &style,
 		 const char *format, va_list args)
 {
-  set_output_style (stream, style);
+  stream->emit_style_escape (style);
   vfprintf_filtered (stream, format, args);
-  set_output_style (stream, ui_file_style ());
+  stream->emit_style_escape (ui_file_style ());
 }
 
 void