Handle very long lines when printing fix-it hints

When fixing PR c/82050 I noticed a bug in how we print fix-it hints
for very long lines: we weren't taking into account the x-offset for
the line when printing the fix-it hint.

This could lead to output where instead of printing:

foo.c:14:3944: error: etc
  = foo.field
        ^~~~~
        replacement

where the lines have been offset to start printing at about column 3900,
the "replacement" line was erroneously *not* offset, and was thus
prefixed by thousands of spaces, leading to large whitespace gaps in
the output, and the replacement failing to line up with the source to be
replaced.

Fixed thusly.

gcc/ChangeLog:
	* diagnostic-show-locus.c (layout::print_trailing_fixits): Handle
	m_x_offset.
	(layout::move_to_column): Likewise.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic-test-show-locus-bw.c
	(test_very_wide_line): Update expected output to include a
	fix-it hint.
	* gcc.dg/plugin/diagnostic-test-show-locus-color.c
	(test_very_wide_line): Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(test_show_locus): Add a fix-it hint to "test_very_wide_line".

From-SVN: r255219

gcc/ChangeLog

+2017-11-28  David Malcolm  <dmalcolm@redhat.com>
+
+	* diagnostic-show-locus.c (layout::print_trailing_fixits): Handle
+	m_x_offset.
+	(layout::move_to_column): Likewise.
+
 2017-11-28  Jakub Jelinek  <jakub@redhat.com>
 
 	PR sanitizer/81275

gcc/diagnostic-show-locus.c

@@ -1691,7 +1691,7 @@ layout::print_trailing_fixits (int row)
   /* Now print the corrections.  */
   unsigned i;
   correction *c;
-  int column = 0;
+  int column = m_x_offset;
 
   FOR_EACH_VEC_ELT (corrections.m_corrections, i, c)
     {
@@ -1845,7 +1845,7 @@ layout::move_to_column (int *column, int dest_column)
   if (*column > dest_column)
     {
       print_newline ();
-      *column = 0;
+      *column = m_x_offset;
     }
 
   while (*column < dest_column)

gcc/testsuite/ChangeLog

+2017-11-28  David Malcolm  <dmalcolm@redhat.com>
+
+	* gcc.dg/plugin/diagnostic-test-show-locus-bw.c
+	(test_very_wide_line): Update expected output to include a
+	fix-it hint.
+	* gcc.dg/plugin/diagnostic-test-show-locus-color.c
+	(test_very_wide_line): Likewise.
+	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
+	(test_show_locus): Add a fix-it hint to "test_very_wide_line".
+
 2017-11-28  Jakub Jelinek  <jakub@redhat.com>
 
 	PR sanitizer/81275

gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw.c

@@ -122,6 +122,7 @@ void test_very_wide_line (void)
  6789012345678901234567890123456789012345678901234567890123456789012345
                                               float f = foo * bar;
                                                         ~~~~^~~~~
+                                                        bar * foo
    { dg-end-multiline-output "" } */
 #endif
 }

gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color.c

@@ -122,6 +122,7 @@ void test_very_wide_line (void)
  6789012345678901234567890123456789012345678901234567890123456789012345
                                               float f = foo * bar;
                                                         ~~~~^~~~~
+                                                        bar * foo
    { dg-end-multiline-output "" } */
 #endif
 }

gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c

@@ -235,9 +235,12 @@ test_show_locus (function *fun)
     {
       const int line = fnstart_line + 2;
       global_dc->show_ruler_p = true;
-      warning_at (make_location (get_loc (line, 94), get_loc (line, 90),
-				 get_loc (line, 98)),
-		  0, "test");
+      rich_location richloc (line_table,
+			     make_location (get_loc (line, 94),
+					    get_loc (line, 90),
+					    get_loc (line, 98)));
+      richloc.add_fixit_replace ("bar * foo");
+      warning_at (&richloc, 0, "test");
       global_dc->show_ruler_p = false;
     }