diagnostics: add line numbers to source (PR other/84889)

This patch adds a left margin to the lines of source (and annotations)
printed by diagnostic_show_locus, so that e.g. rather than:

test.c: In function 'test':
test.c:12:15: error: 'struct foo' has no member named 'm_bar'; did you mean 'bar'?
   return ptr->m_bar;
               ^~~~~
               bar

we print:

test.c: In function 'test':
test.c:12:15: error: 'struct foo' has no member named 'm_bar'; did you mean 'bar'?
12 |   return ptr->m_bar;
   |               ^~~~~
   |               bar

Similarly, for a multiline case (in C++ this time), this:

bad-binary-ops.C: In function 'int test_2()':
bad-binary-ops.C:26:4: error: no match for 'operator+' (operand types are 's' and 't')
   return (some_function ()
           ~~~~~~~~~~~~~~~~
    + some_other_function ());
    ^~~~~~~~~~~~~~~~~~~~~~~~

becomes:

bad-binary-ops.C: In function 'int test_2()':
bad-binary-ops.C:26:4: error: no match for 'operator+' (operand types are 's' and 't')
25 |   return (some_function ()
   |           ~~~~~~~~~~~~~~~~
26 |    + some_other_function ());
   |    ^~~~~~~~~~~~~~~~~~~~~~~~

I believe this slightly improves the readability of the output, in that it:
- distinguishes between the user's source code vs the annotation lines
  that we're adding (the underlinings and fix-it hints here)
- shows the line numbers in another place (potentially helpful for
  multiline diagnostics, where the user can see the line numbers directly,
  rather than have to figure them out relative to the caret: in the 2nd
  example, note how the diagnostic is reported at line 26, but the first
  line printed is actually line 25)

I'm not sure that this is the precise format we want to go with [1], but
I think it's an improvement over the status quo, and we're in stage 1
of gcc 9, so there's plenty of time to shake out issues.

I've turned it on by default; it can be disabled via
-fno-diagnostics-show-line-numbers (it's also turned off in the testsuite, to
avoid breaking numerous existing test cases).

[1] Some possible variants:
  - maybe just "LL|" rather than "LL | "
  - maybe ':' rather than '|'
  - maybe we should have some leading indentation, to better split up
    the diagnostics visually via the left-hand column
  - etc

gcc/ChangeLog:
	PR other/84889
	* common.opt (fdiagnostics-show-line-numbers): New option.
	* diagnostic-show-locus.c (class layout): Add fields
	"m_show_line_numbers_p" and "m_linenum_width";
	(num_digits): New function.
	(test_num_digits): New function.
	(layout::layout): Initialize new fields.  Update m_x_offset
	logic to handle any left margin.
	(layout::print_source_line): Print line number when requested.
	(layout::start_annotation_line): New member function.
	(layout::print_annotation_line): Call it.
	(layout::print_leading_fixits): Likewise.
	(layout::print_trailing_fixits): Likewise.  Update calls to
	move_to_column for new parameter.
	(layout::get_x_bound_for_row): Add "add_left_margin" param and use
	it to potentially call start_annotation_line.
	(layout::show_ruler): Call start_annotation_line.
	(selftest::test_line_numbers_multiline_range): New selftest.
	(selftest::diagnostic_show_locus_c_tests): Call test_num_digits
	and selftest::test_line_numbers_multiline_range.
	* diagnostic.c (diagnostic_initialize): Initialize
	show_line_numbers_p.
	* diagnostic.h (struct diagnostic_context): Add field
	"show_line_numbers_p".
	* doc/invoke.texi (Diagnostic Message Formatting Options): Add
	-fno-diagnostics-show-line-numbers.
	* dwarf2out.c (gen_producer_string): Add
	OPT_fdiagnostics_show_line_numbers to the ignored options.
	* lto-wrapper.c (merge_and_complain): Likewise to the "pick
	one setting" options.
	(append_compiler_options): Likewise to the dropped options.
	(append_diag_options): Likewise to the passed-on options.
	* opts.c (common_handle_option): Handle the new option.
	* toplev.c (general_init): Set up global_dc->show_line_numbers_p.

gcc/testsuite/ChangeLog:
	PR other/84889
	* gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c: New
	test.
	* gcc.dg/plugin/diagnostic-test-show-locus-color-line-numbers.c:
	New test.
	* gcc.dg/plugin/plugin.exp (plugin_test_list): Add the new tests.
	* lib/prune.exp: Add -fno-diagnostics-show-line-numbers to
	TEST_ALWAYS_FLAGS.

From-SVN: r263450

15 files changed, 373 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 601dc7f24bd..dd088bb46a8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,40 @@
+2018-08-09  David Malcolm  <dmalcolm@redhat.com>
+
+	PR other/84889
+	* common.opt (fdiagnostics-show-line-numbers): New option.
+	* diagnostic-show-locus.c (class layout): Add fields
+	"m_show_line_numbers_p" and "m_linenum_width";
+	(num_digits): New function.
+	(test_num_digits): New function.
+	(layout::layout): Initialize new fields.  Update m_x_offset
+	logic to handle any left margin.
+	(layout::print_source_line): Print line number when requested.
+	(layout::start_annotation_line): New member function.
+	(layout::print_annotation_line): Call it.
+	(layout::print_leading_fixits): Likewise.
+	(layout::print_trailing_fixits): Likewise.  Update calls to
+	move_to_column for new parameter.
+	(layout::get_x_bound_for_row): Add "add_left_margin" param and use
+	it to potentially call start_annotation_line.
+	(layout::show_ruler): Call start_annotation_line.
+	(selftest::test_line_numbers_multiline_range): New selftest.
+	(selftest::diagnostic_show_locus_c_tests): Call test_num_digits
+	and selftest::test_line_numbers_multiline_range.
+	* diagnostic.c (diagnostic_initialize): Initialize
+	show_line_numbers_p.
+	* diagnostic.h (struct diagnostic_context): Add field
+	"show_line_numbers_p".
+	* doc/invoke.texi (Diagnostic Message Formatting Options): Add
+	-fno-diagnostics-show-line-numbers.
+	* dwarf2out.c (gen_producer_string): Add
+	OPT_fdiagnostics_show_line_numbers to the ignored options.
+	* lto-wrapper.c (merge_and_complain): Likewise to the "pick
+	one setting" options.
+	(append_compiler_options): Likewise to the dropped options.
+	(append_diag_options): Likewise to the passed-on options.
+	* opts.c (common_handle_option): Handle the new option.
+	* toplev.c (general_init): Set up global_dc->show_line_numbers_p.
+
 2018-08-09  Kelvin Nilsen  <kelvin@gcc.gnu.org>
 
 	* doc/extend.texi (PowerPC AltiVec Built-in Functions Available on
diff --git a/gcc/common.opt b/gcc/common.opt
index 8043cf06c21..b2f2215ecc6 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1233,6 +1233,10 @@ fdiagnostics-show-caret
 Common Var(flag_diagnostics_show_caret) Init(1)
 Show the source line with a caret indicating the column.
 
+fdiagnostics-show-line-numbers
+Common Var(flag_diagnostics_show_line_numbers) Init(1)
+Show line numbers in the left margin when showing source
+
 fdiagnostics-color
 Common Alias(fdiagnostics-color=,always,never)
 ;
diff --git a/gcc/diagnostic-show-locus.c b/gcc/diagnostic-show-locus.c
index cf9e5c202fe..238c689be1a 100644
--- a/gcc/diagnostic-show-locus.c
+++ b/gcc/diagnostic-show-locus.c
@@ -251,6 +251,7 @@ class layout
   void print_source_line (linenum_type row, const char *line, int line_width,
 			  line_bounds *lbounds_out);
   bool should_print_annotation_line_p (linenum_type row) const;
+  void start_annotation_line () const;
   void print_annotation_line (linenum_type row, const line_bounds lbounds);
   void print_trailing_fixits (linenum_type row);
 
@@ -276,7 +277,7 @@ class layout
 		       int last_non_ws);
 
   void
-  move_to_column (int *column, int dest_column);
+  move_to_column (int *column, int dest_column, bool add_left_margin);
 
  private:
   diagnostic_context *m_context;
@@ -286,9 +287,11 @@ class layout
   expanded_location m_exploc;
   colorizer m_colorizer;
   bool m_colorize_source_p;
+  bool m_show_line_numbers_p;
   auto_vec <layout_range> m_layout_ranges;
   auto_vec <const fixit_hint *> m_fixit_hints;
   auto_vec <line_span> m_line_spans;
+  int m_linenum_width;
   int m_x_offset;
 };
 
@@ -805,6 +808,56 @@ fixit_cmp (const void *p_a, const void *p_b)
   return hint_a->get_start_loc () - hint_b->get_start_loc ();
 }
 
+/* Get the number of digits in the decimal representation
+   of VALUE.  */
+
+static int
+num_digits (int value)
+{
+  /* Perhaps simpler to use log10 for this, but doing it this way avoids
+     using floating point.  */
+  gcc_assert (value >= 0);
+
+  if (value == 0)
+    return 1;
+
+  int digits = 0;
+  while (value > 0)
+    {
+      digits++;
+      value /= 10;
+    }
+  return digits;
+}
+
+
+#if CHECKING_P
+
+/* Selftest for num_digits.  */
+
+static void
+test_num_digits ()
+{
+  ASSERT_EQ (1, num_digits (0));
+  ASSERT_EQ (1, num_digits (9));
+  ASSERT_EQ (2, num_digits (10));
+  ASSERT_EQ (2, num_digits (99));
+  ASSERT_EQ (3, num_digits (100));
+  ASSERT_EQ (3, num_digits (999));
+  ASSERT_EQ (4, num_digits (1000));
+  ASSERT_EQ (4, num_digits (9999));
+  ASSERT_EQ (5, num_digits (10000));
+  ASSERT_EQ (5, num_digits (99999));
+  ASSERT_EQ (6, num_digits (100000));
+  ASSERT_EQ (6, num_digits (999999));
+  ASSERT_EQ (7, num_digits (1000000));
+  ASSERT_EQ (7, num_digits (9999999));
+  ASSERT_EQ (8, num_digits (10000000));
+  ASSERT_EQ (8, num_digits (99999999));
+}
+
+#endif /* #if CHECKING_P */
+
 /* Implementation of class layout.  */
 
 /* Constructor for class layout.
@@ -826,9 +879,11 @@ layout::layout (diagnostic_context * context,
   m_exploc (richloc->get_expanded_location (0)),
   m_colorizer (context, diagnostic_kind),
   m_colorize_source_p (context->colorize_source_p),
+  m_show_line_numbers_p (context->show_line_numbers_p),
   m_layout_ranges (richloc->get_num_locations ()),
   m_fixit_hints (richloc->get_num_fixit_hints ()),
   m_line_spans (1 + richloc->get_num_locations ()),
+  m_linenum_width (0),
   m_x_offset (0)
 {
   for (unsigned int idx = 0; idx < richloc->get_num_locations (); idx++)
@@ -854,6 +909,14 @@ layout::layout (diagnostic_context * context,
   /* Populate m_line_spans.  */
   calculate_line_spans ();
 
+  /* Determine m_linenum_width.  */
+  gcc_assert (m_line_spans.length () > 0);
+  const line_span *last_span = &m_line_spans[m_line_spans.length () - 1];
+  int highest_line = last_span->m_last_line;
+  if (highest_line < 0)
+    highest_line = 0;
+  m_linenum_width = num_digits (highest_line);
+
   /* Adjust m_x_offset.
      Center the primary caret to fit in max_width; all columns
      will be adjusted accordingly.  */
@@ -863,6 +926,8 @@ layout::layout (diagnostic_context * context,
     {
       size_t right_margin = CARET_LINE_MARGIN;
       size_t column = m_exploc.column;
+      if (m_show_line_numbers_p)
+	column += m_linenum_width + 2;
       right_margin = MIN (line.length () - column, right_margin);
       right_margin = max_width - right_margin;
       if (line.length () >= max_width && column > right_margin)
@@ -1183,7 +1248,15 @@ layout::print_source_line (linenum_type row, const char *line, int line_width,
 							   line_width);
   line += m_x_offset;
 
-  pp_space (m_pp);
+  if (m_show_line_numbers_p)
+    {
+      int width = num_digits (row);
+      for (int i = 0; i < m_linenum_width - width; i++)
+	pp_space (m_pp);
+      pp_printf (m_pp, "%i | ", row);
+    }
+  else
+    pp_space (m_pp);
   int first_non_ws = INT_MAX;
   int last_non_ws = 0;
   int column;
@@ -1245,6 +1318,20 @@ layout::should_print_annotation_line_p (linenum_type row) const
   return false;
 }
 
+/* Begin an annotation line.  If m_show_line_numbers_p, print the left
+   margin, which is empty for annotation lines.  Otherwise, do nothing.  */
+
+void
+layout::start_annotation_line () const
+{
+  if (m_show_line_numbers_p)
+    {
+      for (int i = 0; i < m_linenum_width; i++)
+	pp_space (m_pp);
+      pp_string (m_pp, " |");
+    }
+}
+
 /* Print a line consisting of the caret/underlines for the given
    source line.  */
 
@@ -1254,7 +1341,9 @@ layout::print_annotation_line (linenum_type row, const line_bounds lbounds)
   int x_bound = get_x_bound_for_row (row, m_exploc.column,
 				     lbounds.m_last_non_ws);
 
+  start_annotation_line ();
   pp_space (m_pp);
+
   for (int column = 1 + m_x_offset; column < x_bound; column++)
     {
       bool in_range_p;
@@ -1316,6 +1405,7 @@ layout::print_leading_fixits (linenum_type row)
 	     helps them stand out from each other, and from
 	     the surrounding text.  */
 	  m_colorizer.set_normal_text ();
+	  start_annotation_line ();
 	  pp_character (m_pp, '+');
 	  m_colorizer.set_fixit_insert ();
 	  /* Print all but the trailing newline of the fix-it hint.
@@ -1712,6 +1802,9 @@ layout::print_trailing_fixits (linenum_type row)
   correction *c;
   int column = m_x_offset;
 
+  if (!corrections.m_corrections.is_empty ())
+    start_annotation_line ();
+
   FOR_EACH_VEC_ELT (corrections.m_corrections, i, c)
     {
       /* For now we assume each fixit hint can only touch one line.  */
@@ -1719,7 +1812,7 @@ layout::print_trailing_fixits (linenum_type row)
 	{
 	  /* This assumes the insertion just affects one line.  */
 	  int start_column = c->m_printed_columns.start;
-	  move_to_column (&column, start_column);
+	  move_to_column (&column, start_column, true);
 	  m_colorizer.set_fixit_insert ();
 	  pp_string (m_pp, c->m_text);
 	  m_colorizer.set_normal_text ();
@@ -1737,7 +1830,7 @@ layout::print_trailing_fixits (linenum_type row)
 					       finish_column)
 	      || c->m_len == 0)
 	    {
-	      move_to_column (&column, start_column);
+	      move_to_column (&column, start_column, true);
 	      m_colorizer.set_fixit_delete ();
 	      for (; column <= finish_column; column++)
 		pp_character (m_pp, '-');
@@ -1748,7 +1841,7 @@ layout::print_trailing_fixits (linenum_type row)
 	     a new line) if we have actual replacement text.  */
 	  if (c->m_len > 0)
 	    {
-	      move_to_column (&column, start_column);
+	      move_to_column (&column, start_column, true);
 	      m_colorizer.set_fixit_insert ();
 	      pp_string (m_pp, c->m_text);
 	      m_colorizer.set_normal_text ();
@@ -1758,7 +1851,7 @@ layout::print_trailing_fixits (linenum_type row)
     }
 
   /* Add a trailing newline, if necessary.  */
-  move_to_column (&column, 0);
+  move_to_column (&column, 0, false);
 }
 
 /* Disable any colorization and emit a newline.  */
@@ -1855,15 +1948,18 @@ layout::get_x_bound_for_row (linenum_type row, int caret_column,
 
 /* Given *COLUMN as an x-coordinate, print spaces to position
    successive output at DEST_COLUMN, printing a newline if necessary,
-   and updating *COLUMN.  */
+   and updating *COLUMN.  If ADD_LEFT_MARGIN, then print the (empty)
+   left margin after any newline.  */
 
 void
-layout::move_to_column (int *column, int dest_column)
+layout::move_to_column (int *column, int dest_column, bool add_left_margin)
 {
   /* Start a new line if we need to.  */
   if (*column > dest_column)
     {
       print_newline ();
+      if (add_left_margin)
+	start_annotation_line ();
       *column = m_x_offset;
     }
 
@@ -1883,6 +1979,7 @@ layout::show_ruler (int max_column) const
   /* Hundreds.  */
   if (max_column > 99)
     {
+      start_annotation_line ();
       pp_space (m_pp);
       for (int column = 1 + m_x_offset; column <= max_column; column++)
 	if (column % 10 == 0)
@@ -1893,6 +1990,7 @@ layout::show_ruler (int max_column) const
     }
 
   /* Tens.  */
+  start_annotation_line ();
   pp_space (m_pp);
   for (int column = 1 + m_x_offset; column <= max_column; column++)
     if (column % 10 == 0)
@@ -1902,6 +2000,7 @@ layout::show_ruler (int max_column) const
   pp_newline (m_pp);
 
   /* Units.  */
+  start_annotation_line ();
   pp_space (m_pp);
   for (int column = 1 + m_x_offset; column <= max_column; column++)
     pp_character (m_pp, '0' + (column % 10));
@@ -3139,12 +3238,58 @@ test_fixit_deletion_affecting_newline (const line_table_case &case_)
 		pp_formatted_text (dc.printer));
 }
 
+/* Verify that line numbers are correctly printed for the case of
+   a multiline range in which the width of the line numbers changes
+   (e.g. from "9" to "10").  */
+
+static void
+test_line_numbers_multiline_range ()
+{
+  /* Create a tempfile and write some text to it.  */
+  pretty_printer pp;
+  for (int i = 0; i < 20; i++)
+    /* .........0000000001111111.
+   .............1234567890123456.  */
+    pp_printf (&pp, "this is line %i\n", i + 1);
+  temp_source_file tmp (SELFTEST_LOCATION, ".txt", pp_formatted_text (&pp));
+  line_table_test ltt;
+
+  const line_map_ordinary *ord_map = linemap_check_ordinary
+    (linemap_add (line_table, LC_ENTER, false, tmp.get_filename (), 0));
+  linemap_line_start (line_table, 1, 100);
+
+  /* Create a multi-line location, starting at the "line" of line 9, with
+     a caret on the "is" of line 10, finishing on the "this" line 11.  */
+
+  location_t start
+    = linemap_position_for_line_and_column (line_table, ord_map, 9, 9);
+  location_t caret
+    = linemap_position_for_line_and_column (line_table, ord_map, 10, 6);
+  location_t finish
+    = linemap_position_for_line_and_column (line_table, ord_map, 11, 4);
+  location_t loc = make_location (caret, start, finish);
+
+  test_diagnostic_context dc;
+  dc.show_line_numbers_p = true;
+  gcc_rich_location richloc (loc);
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" 9 | this is line 9\n"
+		"   |         ~~~~~~\n"
+		"10 | this is line 10\n"
+		"   | ~~~~~^~~~~~~~~~\n"
+		"11 | this is line 11\n"
+		"   | ~~~~  \n",
+		pp_formatted_text (dc.printer));
+}
+
 /* Run all of the selftests within this file.  */
 
 void
 diagnostic_show_locus_c_tests ()
 {
   test_line_span ();
+  test_num_digits ();
 
   test_layout_range_for_single_point ();
   test_layout_range_for_single_line ();
@@ -3164,6 +3309,8 @@ diagnostic_show_locus_c_tests ()
   for_each_line_table_case (test_fixit_insert_containing_newline_2);
   for_each_line_table_case (test_fixit_replace_containing_newline);
   for_each_line_table_case (test_fixit_deletion_affecting_newline);
+
+  test_line_numbers_multiline_range ();
 }
 
 } // namespace selftest
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index 3d7f164f94e..e9d93d531d5 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -175,6 +175,7 @@ diagnostic_initialize (diagnostic_context *context, int n_opts)
   context->lock = 0;
   context->inhibit_notes_p = false;
   context->colorize_source_p = false;
+  context->show_line_numbers_p = false;
   context->show_ruler_p = false;
   context->parseable_fixits_p = false;
   context->edit_context_ptr = NULL;
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index cf3a610f3d9..744aec1a68f 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -204,6 +204,10 @@ struct diagnostic_context
      a token, which would look strange).  */
   bool colorize_source_p;
 
+  /* When printing source code, should there be a left-hand margin
+     showing line numbers?  */
+  bool show_line_numbers_p;
+
   /* Usable by plugins; if true, print a debugging ruler above the
      source output.  */
   bool show_ruler_p;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 438274e67f8..0e9a9c3e2f7 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -267,6 +267,7 @@ Objective-C and Objective-C++ Dialects}.
 -fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}  @gol
 -fdiagnostics-color=@r{[}auto@r{|}never@r{|}always@r{]}  @gol
 -fno-diagnostics-show-option  -fno-diagnostics-show-caret @gol
+-fno-diagnostics-show-line-numbers @gol
 -fdiagnostics-parseable-fixits  -fdiagnostics-generate-patch @gol
 -fdiagnostics-show-template-tree -fno-elide-type @gol
 -fno-show-column}
@@ -3710,6 +3711,13 @@ the @option{-fmessage-length=n} option is given.  When the output is done
 to the terminal, the width is limited to the width given by the
 @env{COLUMNS} environment variable or, if not set, to the terminal width.
 
+@item -fno-diagnostics-show-line-numbers
+@opindex fno-diagnostics-show-line-numbers
+@opindex fdiagnostics-show-line-numbers
+By default, when printing source code (via @option{-fdiagnostics-show-caret}),
+a left margin is printed, showing line numbers.  This option suppresses this
+left margin.
+
 @item -fdiagnostics-parseable-fixits
 @opindex fdiagnostics-parseable-fixits
 Emit fix-it hints in a machine-parseable format, suitable for consumption
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index b67481dd2db..9ed473088e7 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -24247,6 +24247,7 @@ gen_producer_string (void)
       case OPT_fdiagnostics_show_location_:
       case OPT_fdiagnostics_show_option:
       case OPT_fdiagnostics_show_caret:
+      case OPT_fdiagnostics_show_line_numbers:
       case OPT_fdiagnostics_color_:
       case OPT_fverbose_asm:
       case OPT____:
diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
index cf4a8c659e0..39d9f088bc6 100644
--- a/gcc/lto-wrapper.c
+++ b/gcc/lto-wrapper.c
@@ -255,6 +255,7 @@ merge_and_complain (struct cl_decoded_option **decoded_options,
 
 	  /* Fallthru.  */
 	case OPT_fdiagnostics_show_caret:
+	case OPT_fdiagnostics_show_line_numbers:
 	case OPT_fdiagnostics_show_option:
 	case OPT_fdiagnostics_show_location_:
 	case OPT_fshow_column:
@@ -536,6 +537,7 @@ append_compiler_options (obstack *argv_obstack, struct cl_decoded_option *opts,
       switch (option->opt_index)
 	{
 	case OPT_fdiagnostics_show_caret:
+	case OPT_fdiagnostics_show_line_numbers:
 	case OPT_fdiagnostics_show_option:
 	case OPT_fdiagnostics_show_location_:
 	case OPT_fshow_column:
@@ -582,6 +584,7 @@ append_diag_options (obstack *argv_obstack, struct cl_decoded_option *opts,
 	{
 	case OPT_fdiagnostics_color_:
 	case OPT_fdiagnostics_show_caret:
+	case OPT_fdiagnostics_show_line_numbers:
 	case OPT_fdiagnostics_show_option:
 	case OPT_fdiagnostics_show_location_:
 	case OPT_fshow_column:
diff --git a/gcc/opts.c b/gcc/opts.c
index 17d91988ada..4153263fcab 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -2175,6 +2175,10 @@ common_handle_option (struct gcc_options *opts,
       dc->show_caret = value;
       break;
 
+    case OPT_fdiagnostics_show_line_numbers:
+      dc->show_line_numbers_p = value;
+      break;
+
     case OPT_fdiagnostics_color_:
       diagnostic_color_init (dc, value);
       break;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b59b4bbd3b1..3da9f3baa36 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,14 @@
+2018-08-09  David Malcolm  <dmalcolm@redhat.com>
+
+	PR other/84889
+	* gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c: New
+	test.
+	* gcc.dg/plugin/diagnostic-test-show-locus-color-line-numbers.c:
+	New test.
+	* gcc.dg/plugin/plugin.exp (plugin_test_list): Add the new tests.
+	* lib/prune.exp: Add -fno-diagnostics-show-line-numbers to
+	TEST_ALWAYS_FLAGS.
+
 2018-08-09  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR tree-optimization/86858
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c
new file mode 100644
index 00000000000..66a2faae40d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c
@@ -0,0 +1,115 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdiagnostics-show-caret -fdiagnostics-show-line-numbers" } */
+
+/* This is a collection of unittests for diagnostic_show_locus;
+   see the overview in diagnostic_plugin_test_show_locus.c.
+
+   In particular, note the discussion of why we need a very long line here:
+01234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
+   and that we can't use macros in this file.  */
+
+void test_simple (void)
+{
+#if 0
+  myvar = myvar.x; /* { dg-warning "test" } */
+
+/* { dg-begin-multiline-output "" }
+14 |   myvar = myvar.x;
+   |           ~~~~~^~
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+void test_multiline (void)
+{
+#if 0
+  x = (first_function ()
+       + second_function ()); /* { dg-warning "test" } */
+
+/* { dg-begin-multiline-output "" }
+26 |   x = (first_function ()
+   |        ~~~~~~~~~~~~~~~~~
+27 |        + second_function ());
+   |        ^ ~~~~~~~~~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+void test_very_wide_line (void)
+{
+#if 0
+                                                                                float f = foo * bar; /* { dg-warning "95: test" } */
+/* { dg-begin-multiline-output "" }
+   | 0         0         0         0         0         0         1         
+   | 4         5         6         7         8         9         0         
+   | 0123456789012345678901234567890123456789012345678901234567890123456789
+41 |                                          float f = foo * bar;
+   |                                                    ~~~~^~~~~
+   |                                                    bar * foo
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+/* Unit test for rendering of insertion fixit hints
+   (example taken from PR 62316).  */
+
+void test_fixit_insert (void)
+{
+#if 0
+   int a[2][2] = { 0, 1 , 2, 3 }; /* { dg-warning "insertion hints" } */
+/* { dg-begin-multiline-output "" }
+59 |    int a[2][2] = { 0, 1 , 2, 3 };
+   |                    ^~~~
+   |                    {   }
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+/* Unit test for rendering of "remove" fixit hints.  */
+
+void test_fixit_remove (void)
+{
+#if 0
+  int a;; /* { dg-warning "example of a removal hint" } */
+/* { dg-begin-multiline-output "" }
+73 |   int a;;
+   |         ^
+   |         -
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+/* Unit test for rendering of "replace" fixit hints.  */
+
+void test_fixit_replace (void)
+{
+#if 0
+  gtk_widget_showall (dlg); /* { dg-warning "example of a replacement hint" } */
+/* { dg-begin-multiline-output "" }
+87 |   gtk_widget_showall (dlg);
+   |   ^~~~~~~~~~~~~~~~~~
+   |   gtk_widget_show_all
+   { dg-end-multiline-output "" } */
+#endif
+}
+
+
+/* Unit test for rendering of fix-it hints that add new lines.  */
+
+void test_fixit_insert_newline (void)
+{
+#if 0
+  switch (op)
+    {
+    case 'a':
+      x = a;
+    case 'b':  /* { dg-warning "newline insertion" } */
+      x = b;
+    }
+/* { dg-begin-multiline-output "" }
+    |+      break;
+106 |     case 'b':
+    |     ^~~~~~~~
+   { dg-end-multiline-output "" } */
+#endif
+}
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color-line-numbers.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color-line-numbers.c
new file mode 100644
index 00000000000..a80b6de3e68
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color-line-numbers.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdiagnostics-show-caret -fplugin-arg-diagnostic_plugin_test_show_locus-color -fdiagnostics-show-line-numbers" } */
+
+/* This is a collection of unittests for diagnostic_show_locus;
+   see the overview in diagnostic_plugin_test_show_locus.c.
+
+   In particular, note the discussion of why we need a very long line here:
+01234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
+   and that we can't use macros in this file.  */
+
+void test_multiline (void)
+{
+#if 0
+  x = (first_function ()
+       + second_function ()); /* { dg-warning "test" } */
+
+/* { dg-begin-multiline-output "" }
+14 |   x = (first_function ()
+   |        ~~~~~~~~~~~~~~~~~
+15 |        + second_function ());
+   |        ^ ~~~~~~~~~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+#endif
+}
diff --git a/gcc/testsuite/gcc.dg/plugin/plugin.exp b/gcc/testsuite/gcc.dg/plugin/plugin.exp
index 5a19fc907e8..b2f8507338a 100644
--- a/gcc/testsuite/gcc.dg/plugin/plugin.exp
+++ b/gcc/testsuite/gcc.dg/plugin/plugin.exp
@@ -72,8 +72,10 @@ set plugin_test_list [list \
     { diagnostic_plugin_test_show_locus.c \
 	  diagnostic-test-show-locus-bw.c \
 	  diagnostic-test-show-locus-color.c \
+	  diagnostic-test-show-locus-bw-line-numbers.c \
+	  diagnostic-test-show-locus-color-line-numbers.c \
 	  diagnostic-test-show-locus-parseable-fixits.c \
-	  diagnostic-test-show-locus-generate-patch.c } \
+	  diagnostic-test-show-locus-generate-patch.c }\
     { diagnostic_plugin_test_tree_expression_range.c \
 	  diagnostic-test-expressions-1.c } \
     { diagnostic_plugin_show_trees.c \
diff --git a/gcc/testsuite/lib/prune.exp b/gcc/testsuite/lib/prune.exp
index 1e11dc9c6ff..df36c345341 100644
--- a/gcc/testsuite/lib/prune.exp
+++ b/gcc/testsuite/lib/prune.exp
@@ -21,7 +21,7 @@ load_lib multiline.exp
 if ![info exists TEST_ALWAYS_FLAGS] {
     set TEST_ALWAYS_FLAGS ""
 }
-set TEST_ALWAYS_FLAGS "-fno-diagnostics-show-caret -fdiagnostics-color=never $TEST_ALWAYS_FLAGS"
+set TEST_ALWAYS_FLAGS "-fno-diagnostics-show-caret -fno-diagnostics-show-line-numbers -fdiagnostics-color=never $TEST_ALWAYS_FLAGS"
 
 proc prune_gcc_output { text } {
     global srcdir
diff --git a/gcc/toplev.c b/gcc/toplev.c
index f23e8aeb17b..aa943a8655e 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1112,6 +1112,8 @@ general_init (const char *argv0, bool init_signals)
 
   global_dc->show_caret
     = global_options_init.x_flag_diagnostics_show_caret;
+  global_dc->show_line_numbers_p
+    = global_options_init.x_flag_diagnostics_show_line_numbers;
   global_dc->show_option_requested
     = global_options_init.x_flag_diagnostics_show_option;
   global_dc->show_column