[committed] diagnostics: add minimum width to left margin for line numbers

diff --git a/gcc/common.opt b/gcc/common.opt
index 53aac19..2971dc2 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1281,6 +1281,10 @@  fdiagnostics-show-option
 Common Var(flag_diagnostics_show_option) Init(1)
 Amend appropriate diagnostic messages with the command line option that controls them.
 
+fdiagnostics-minimum-margin-width=
+Common Joined UInteger Var(diagnostics_minimum_margin_width) Init(6)
+Set minimum width of left margin of source code when showing source
+
 fdisable-
 Common Joined RejectNegative Var(common_deferred_options) Defer
 -fdisable-[tree|rtl|ipa]-<pass>=range1+range2 disables an optimization pass.
diff --git a/gcc/diagnostic-show-locus.c b/gcc/diagnostic-show-locus.c
index 43a49ea..a42ff81 100644
--- a/gcc/diagnostic-show-locus.c
+++ b/gcc/diagnostic-show-locus.c
@@ -930,6 +930,9 @@  layout::layout (diagnostic_context * context,
   /* If we're showing jumps in the line-numbering, allow at least 3 chars.  */
   if (m_line_spans.length () > 1)
     m_linenum_width = MAX (m_linenum_width, 3);
+  /* If there's a minimum margin width, apply it (subtracting 1 for the space
+     after the line number.  */
+  m_linenum_width = MAX (m_linenum_width, context->min_margin_width - 1);
 
   /* Adjust m_x_offset.
      Center the primary caret to fit in max_width; all columns
@@ -1386,7 +1389,12 @@  layout::start_annotation_line (char margin_char) const
 {
   if (m_show_line_numbers_p)
     {
-      for (int i = 0; i < m_linenum_width; i++)
+      /* Print the margin.  If MARGIN_CHAR != ' ', then print up to 3
+	 of it, right-aligned, padded with spaces.  */
+      int i;
+      for (i = 0; i < m_linenum_width - 3; i++)
+	pp_space (m_pp);
+      for (; i < m_linenum_width; i++)
 	pp_character (m_pp, margin_char);
       pp_string (m_pp, " |");
     }
@@ -3027,12 +3035,12 @@  test_diagnostic_show_locus_fixit_lines (const line_table_case &case_)
     dc.show_line_numbers_p = true;
     diagnostic_show_locus (&dc, &richloc, DK_ERROR);
     ASSERT_STREQ ("\n"
-		  "  3 |                        y\n"
-		  "    |                        .\n"
-		  "....\n"
-		  "  6 |                         : 0.0};\n"
-		  "    |                         ^\n"
-		  "    |                         =\n",
+		  "    3 |                        y\n"
+		  "      |                        .\n"
+		  "......\n"
+		  "    6 |                         : 0.0};\n"
+		  "      |                         ^\n"
+		  "      |                         =\n",
 		  pp_formatted_text (dc.printer));
   }
 }
@@ -3523,10 +3531,10 @@  test_fixit_insert_containing_newline (const line_table_case &case_)
       dc.show_line_numbers_p = true;
       diagnostic_show_locus (&dc, &richloc, DK_ERROR);
       ASSERT_STREQ ("\n"
-		    "2 |       x = a;\n"
-		    "+ |+      break;\n"
-		    "3 |     case 'b':\n"
-		    "  |     ^~~~~~~~~\n",
+		    "    2 |       x = a;\n"
+		    "  +++ |+      break;\n"
+		    "    3 |     case 'b':\n"
+		    "      |     ^~~~~~~~~\n",
 		    pp_formatted_text (dc.printer));
     }
   }
@@ -3605,11 +3613,11 @@  test_fixit_insert_containing_newline_2 (const line_table_case &case_)
     dc.show_line_numbers_p = true;
     diagnostic_show_locus (&dc, &richloc, DK_ERROR);
     ASSERT_STREQ ("\n"
-		  "+ |+#include <stdio.h>\n"
-		  "1 | test (int ch)\n"
-		  "2 | {\n"
-		  "3 |  putchar (ch);\n"
-		  "  |  ^~~~~~~\n",
+		  "  +++ |+#include <stdio.h>\n"
+		  "    1 | test (int ch)\n"
+		  "    2 | {\n"
+		  "    3 |  putchar (ch);\n"
+		  "      |  ^~~~~~~\n",
 		  pp_formatted_text (dc.printer));
   }
 }
@@ -3734,6 +3742,7 @@  test_line_numbers_multiline_range ()
 
   test_diagnostic_context dc;
   dc.show_line_numbers_p = true;
+  dc.min_margin_width = 0;
   gcc_rich_location richloc (loc);
   diagnostic_show_locus (&dc, &richloc, DK_ERROR);
   ASSERT_STREQ ("\n"
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index 8575065..a572c08 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -177,6 +177,7 @@  diagnostic_initialize (diagnostic_context *context, int n_opts)
   context->colorize_source_p = false;
   context->show_labels_p = false;
   context->show_line_numbers_p = false;
+  context->min_margin_width = 0;
   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 d4c605e..3498a9b 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -211,6 +211,10 @@  struct diagnostic_context
      showing line numbers?  */
   bool show_line_numbers_p;
 
+  /* If printing source code, what should the minimum width of the margin
+     be?  Line numbers will be right-aligned, and padded to this width.  */
+  int min_margin_width;
+
   /* 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 802cc64..06a00a2 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -270,6 +270,7 @@  Objective-C and Objective-C++ Dialects}.
 -fdiagnostics-color=@r{[}auto@r{|}never@r{|}always@r{]}  @gol
 -fno-diagnostics-show-option  -fno-diagnostics-show-caret @gol
 -fno-diagnostics-show-labels -fno-diagnostics-show-line-numbers @gol
+-fdiagnostics-minimum-margin-width=@var{width} @gol
 -fdiagnostics-parseable-fixits  -fdiagnostics-generate-patch @gol
 -fdiagnostics-show-template-tree -fno-elide-type @gol
 -fno-show-column}
@@ -3819,6 +3820,11 @@  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-minimum-margin-width=@var{width}
+@opindex -fdiagnostics-minimum-margin-width
+This option controls the minimum width of the left margin printed by
+@option{-fdiagnostics-show-line-numbers}.  It defaults to 6.
+
 @item -fdiagnostics-parseable-fixits
 @opindex fdiagnostics-parseable-fixits
 Emit fix-it hints in a machine-parseable format, suitable for consumption
diff --git a/gcc/opts.c b/gcc/opts.c
index dc12c2e..3b61e17 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -2228,6 +2228,10 @@  common_handle_option (struct gcc_options *opts,
       dc->show_option_requested = value;
       break;
 
+    case OPT_fdiagnostics_minimum_margin_width_:
+      dc->min_margin_width = value;
+      break;
+
     case OPT_fdump_:
       /* Deferred.  */
       break;
diff --git a/gcc/selftest-diagnostic.c b/gcc/selftest-diagnostic.c
index f3c255e..4a7f0de 100644
--- a/gcc/selftest-diagnostic.c
+++ b/gcc/selftest-diagnostic.c
@@ -40,6 +40,7 @@  test_diagnostic_context::test_diagnostic_context ()
   show_labels_p = true;
   show_column = true;
   start_span = start_span_cb;
+  min_margin_width = 6;
 }
 
 test_diagnostic_context::~test_diagnostic_context ()
diff --git a/gcc/testsuite/gcc.dg/missing-header-fixit-3.c b/gcc/testsuite/gcc.dg/missing-header-fixit-3.c
index a692b4d..dd53bf6 100644
--- a/gcc/testsuite/gcc.dg/missing-header-fixit-3.c
+++ b/gcc/testsuite/gcc.dg/missing-header-fixit-3.c
@@ -10,12 +10,12 @@  void test (int i, int j)
   /* { dg-message "include '<stdio.h>' or provide a declaration of 'printf'" "" { target *-*-* } 1 } */
 #if 0
 /* { dg-begin-multiline-output "" }
-9 |   printf ("%i of %i\n", i, j);
-  |   ^~~~~~
+    9 |   printf ("%i of %i\n", i, j);
+      |   ^~~~~~
    { dg-end-multiline-output "" } */
 /* { dg-begin-multiline-output "" }
-+ |+#include <stdio.h>
-1 | /* Example of a fix-it hint that adds a #include directive,
+  +++ |+#include <stdio.h>
+    1 | /* Example of a fix-it hint that adds a #include directive,
    { dg-end-multiline-output "" } */
 #endif
 }
diff --git a/gcc/testsuite/gcc.dg/missing-header-fixit-4.c b/gcc/testsuite/gcc.dg/missing-header-fixit-4.c
index 0ed3e2c..942897d 100644
--- a/gcc/testsuite/gcc.dg/missing-header-fixit-4.c
+++ b/gcc/testsuite/gcc.dg/missing-header-fixit-4.c
@@ -11,13 +11,13 @@  void test (int i, int j)
   /* { dg-warning "implicit declaration of function" "" { target *-*-* } printf } */
   /* { dg-warning "incompatible implicit declaration" "" { target *-*-* } printf } */
   /* { dg-begin-multiline-output "" }
-10 |   printf ("%i of %i\n", i, j);
-   |   ^~~~~~
+   10 |   printf ("%i of %i\n", i, j);
+      |   ^~~~~~
    { dg-end-multiline-output "" } */
   /* { dg-message "include '<stdio.h>' or provide a declaration of 'printf'" "" { target *-*-* } 4 } */
   /* { dg-begin-multiline-output "" }
-3 | #include "empty.h"
-+ |+#include <stdio.h>
-4 | int the_next_line;
+    3 | #include "empty.h"
+  +++ |+#include <stdio.h>
+    4 | int the_next_line;
    { dg-end-multiline-output "" } */
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers-2.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers-2.c
new file mode 100644
index 0000000..a9d022a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers-2.c
@@ -0,0 +1,22 @@ 
+/* { dg-do compile } */
+/* Verify "-fdiagnostics-minimum-margin-width=0".  */
+/* { dg-options "-O -fdiagnostics-show-caret -fdiagnostics-show-line-numbers -fdiagnostics-minimum-margin-width=0" } */
+
+/* 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 "" }
+15 |   myvar = myvar.x;
+   |           ~~~~~^~
+   { dg-end-multiline-output "" } */
+#endif
+}
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
index 63e5855..1e8f73b 100644
--- 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
@@ -14,8 +14,8 @@  void test_simple (void)
   myvar = myvar.x; /* { dg-warning "test" } */
 
 /* { dg-begin-multiline-output "" }
-14 |   myvar = myvar.x;
-   |           ~~~~~^~
+   14 |   myvar = myvar.x;
+      |           ~~~~~^~
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -27,12 +27,12 @@  void test_multiline (void)
        + second_function ()); /* { dg-warning "test" } */
 
 /* { dg-begin-multiline-output "" }
-26 |   x = (first_function ()
-   |        ~~~~~~~~~~~~~~~~~
-27 |        + second_function ());
-   |        ^ ~~~~~~~~~~~~~~~~~~
-   |        |
-   |        label
+   26 |   x = (first_function ()
+      |        ~~~~~~~~~~~~~~~~~
+   27 |        + second_function ());
+      |        ^ ~~~~~~~~~~~~~~~~~~
+      |        |
+      |        label
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -42,14 +42,14 @@  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
-43 |                                          float f = foo * bar;
-   |                                                    ~~~~^~~~~
-   |                                                        |
-   |                                                        label
-   |                                                    bar * foo
+      |        0         0         0         0         0         1         1  
+      |        5         6         7         8         9         0         1  
+      | 3456789012345678901234567890123456789012345678901234567890123456789012
+   43 |                                       float f = foo * bar;
+      |                                                 ~~~~^~~~~
+      |                                                     |
+      |                                                     label 0
+      |                                                 bar * foo
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -62,9 +62,9 @@  void test_fixit_insert (void)
 #if 0
    int a[2][2] = { 0, 1 , 2, 3 }; /* { dg-warning "insertion hints" } */
 /* { dg-begin-multiline-output "" }
-63 |    int a[2][2] = { 0, 1 , 2, 3 };
-   |                    ^~~~
-   |                    {   }
+   63 |    int a[2][2] = { 0, 1 , 2, 3 };
+      |                    ^~~~
+      |                    {   }
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -76,9 +76,9 @@  void test_fixit_remove (void)
 #if 0
   int a;; /* { dg-warning "example of a removal hint" } */
 /* { dg-begin-multiline-output "" }
-77 |   int a;;
-   |         ^
-   |         -
+   77 |   int a;;
+      |         ^
+      |         -
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -90,9 +90,9 @@  void test_fixit_replace (void)
 #if 0
   gtk_widget_showall (dlg); /* { dg-warning "example of a replacement hint" } */
 /* { dg-begin-multiline-output "" }
-91 |   gtk_widget_showall (dlg);
-   |   ^~~~~~~~~~~~~~~~~~
-   |   gtk_widget_show_all
+   91 |   gtk_widget_showall (dlg);
+      |   ^~~~~~~~~~~~~~~~~~
+      |   gtk_widget_show_all
    { dg-end-multiline-output "" } */
 #endif
 }
@@ -111,10 +111,10 @@  void test_fixit_insert_newline (void)
       x = b;
     }
 /* { dg-begin-multiline-output "" }
-109 |       x = a;
-+++ |+      break;
-110 |     case 'b':
-    |     ^~~~~~~~
+  109 |       x = a;
+  +++ |+      break;
+  110 |     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
index 0453c52..bb83862 100644
--- 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
@@ -15,12 +15,12 @@  void test_multiline (void)
        + second_function ()); /* { dg-warning "test" } */
 
 /* { dg-begin-multiline-output "" }
-14 |   x = (first_function ()
-   |        ~~~~~~~~~~~~~~~~~
-15 |        + second_function ());
-   |        ^ ~~~~~~~~~~~~~~~~~~
-   |        |
-   |        label
+   14 |   x = (first_function ()
+      |        ~~~~~~~~~~~~~~~~~
+   15 |        + second_function ());
+      |        ^ ~~~~~~~~~~~~~~~~~~
+      |        |
+      |        label
    { dg-end-multiline-output "" } */
 #endif
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/plugin.exp b/gcc/testsuite/gcc.dg/plugin/plugin.exp
index 1d06c04..d92ede7 100644
--- a/gcc/testsuite/gcc.dg/plugin/plugin.exp
+++ b/gcc/testsuite/gcc.dg/plugin/plugin.exp
@@ -76,6 +76,7 @@  set plugin_test_list [list \
 	  diagnostic-test-show-locus-color.c \
 	  diagnostic-test-show-locus-no-labels.c \
 	  diagnostic-test-show-locus-bw-line-numbers.c \
+	  diagnostic-test-show-locus-bw-line-numbers-2.c \
 	  diagnostic-test-show-locus-color-line-numbers.c \
 	  diagnostic-test-show-locus-parseable-fixits.c \
 	  diagnostic-test-show-locus-generate-patch.c }\
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 9fb83d4..d7ea11a 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1120,6 +1120,8 @@  general_init (const char *argv0, bool init_signals)
     = global_options_init.x_flag_diagnostics_show_line_numbers;
   global_dc->show_option_requested
     = global_options_init.x_flag_diagnostics_show_option;
+  global_dc->min_margin_width
+    = global_options_init.x_diagnostics_minimum_margin_width;
   global_dc->show_column
     = global_options_init.x_flag_show_column;
   global_dc->internal_error = internal_error_function;