[committed] Handle very long lines when printing fix-it hints

[David Malcolm]

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.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu.
Committed to trunk as r255219.

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".
---
 gcc/diagnostic-show-locus.c                                     | 4 ++--
 gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw.c     | 1 +
 gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color.c  | 1 +
 gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c | 9 ++++++---
 4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/gcc/diagnostic-show-locus.c b/gcc/diagnostic-show-locus.c
index a1ce682..387c245 100644
--- a/gcc/diagnostic-show-locus.c
+++ b/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)
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw.c 
b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw.c
index 100fa38..513c0af 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw.c
+++ b/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
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color.c 
b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color.c
index 3fb1c24..4cc406d 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-color.c
+++ b/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
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c 
b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
index 9751e1c..3908b92 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
+++ b/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;
     }
 
-- 
1.8.5.3