Add diagnostic paths

This patch adds support for associating a "diagnostic_path" with a
diagnostic: a sequence of events predicted by the compiler that leads to
the problem occurring, with their locations in the user's source,
text descriptions, and stack information (for handling interprocedural
paths).

For example, the following (hypothetical) error has a 3-event
intraprocedural path:

test.c: In function 'demo':
test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which
  requires a non-NULL parameter
   29 |     PyList_Append(list, item);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~
  'demo': events 1-3
     |
     |   25 |   list = PyList_New(0);
     |      |          ^~~~~~~~~~~~~
     |      |          |
     |      |          (1) when 'PyList_New' fails, returning NULL
     |   26 |
     |   27 |   for (i = 0; i < count; i++) {
     |      |   ~~~
     |      |   |
     |      |   (2) when 'i < count'
     |   28 |     item = PyLong_FromLong(random());
     |   29 |     PyList_Append(list, item);
     |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
     |      |     |
     |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
     |

The patch adds a new "%@" format code for printing event IDs, so that
in the above, the description of event (3) mentions event (1), showing
the user where the bogus NULL value comes from (the event IDs are
colorized to draw the user's attention to them).

There is a separation between data vs presentation: the above shows how
the diagnostic-printing code has consolidated the path into a single run
of events, since all the events are near each other and within the same
function; more complicated examples (such as interprocedural paths)
might be printed as multiple runs of events.

Examples of how interprocedural paths are printed can be seen in the
test suite (which uses a plugin to exercise the code without relying
on specific warnings using this functionality).

Other output formats include
- JSON,
- printing each event as a separate "note", and
- to not emit paths.

gcc/ChangeLog:
	* Makefile.in (OBJS): Add tree-diagnostic-path.o.
	* common.opt (fdiagnostics-path-format=): New option.
	(diagnostic_path_format): New enum.
	(fdiagnostics-show-path-depths): New option.
	* coretypes.h (diagnostic_event_id_t): New forward decl.
	* diagnostic-color.c (color_dict): Add "path".
	* diagnostic-event-id.h: New file.
	* diagnostic-format-json.cc (json_from_expanded_location): Make
	non-static.
	(json_end_diagnostic): Call context->make_json_for_path if it
	exists and the diagnostic has a path.
	(diagnostic_output_format_init): Clear context->print_path.
	* diagnostic-path.h: New file.
	* diagnostic-show-locus.c (colorizer::set_range): Special-case
	when printing a run of events in a diagnostic_path so that they
	all get the same color.
	(layout::m_diagnostic_path_p): New field.
	(layout::layout): Initialize it.
	(layout::print_any_labels): Don't colorize the label text for an
	event in a diagnostic_path.
	(gcc_rich_location::add_location_if_nearby): Add
	"restrict_to_current_line_spans" and "label" params.  Pass the
	former to layout.maybe_add_location_range; pass the latter
	when calling add_range.
	* diagnostic.c: Include "diagnostic-path.h".
	(diagnostic_initialize): Initialize context->path_format and
	context->show_path_depths.
	(diagnostic_show_any_path): New function.
	(diagnostic_path::interprocedural_p): New function.
	(diagnostic_report_diagnostic): Call diagnostic_show_any_path.
	(simple_diagnostic_path::num_events): New function.
	(simple_diagnostic_path::get_event): New function.
	(simple_diagnostic_path::add_event): New function.
	(simple_diagnostic_event::simple_diagnostic_event): New ctor.
	(simple_diagnostic_event::~simple_diagnostic_event): New dtor.
	(debug): New overload taking a diagnostic_path *.
	* diagnostic.def (DK_DIAGNOSTIC_PATH): New.
	* diagnostic.h (enum diagnostic_path_format): New enum.
	(json::value): New forward decl.
	(diagnostic_context::path_format): New field.
	(diagnostic_context::show_path_depths): New field.
	(diagnostic_context::print_path): New callback field.
	(diagnostic_context::make_json_for_path): New callback field.
	(diagnostic_show_any_path): New decl.
	(json_from_expanded_location): New decl.
	* doc/invoke.texi (-fdiagnostics-path-format=): New option.
	(-fdiagnostics-show-path-depths): New option.
	(-fdiagnostics-color): Add "path" to description of default
	GCC_COLORS; describe it.
	(-fdiagnostics-format=json): Document how diagnostic paths are
	represented in the JSON output format.
	* gcc-rich-location.h (gcc_rich_location::add_location_if_nearby):
	Add optional params "restrict_to_current_line_spans" and "label".
	* opts.c (common_handle_option): Handle
	OPT_fdiagnostics_path_format_ and
	OPT_fdiagnostics_show_path_depths.
	* pretty-print.c: Include "diagnostic-event-id.h".
	(pp_format): Implement "%@" format code for printing
	diagnostic_event_id_t *.
	(selftest::test_pp_format): Add tests for "%@".
	* selftest-run-tests.c (selftest::run_tests): Call
	selftest::tree_diagnostic_path_cc_tests.
	* selftest.h (selftest::tree_diagnostic_path_cc_tests): New decl.
	* toplev.c (general_init): Initialize global_dc->path_format and
	global_dc->show_path_depths.
	* tree-diagnostic-path.cc: New file.
	* tree-diagnostic.c (maybe_unwind_expanded_macro_loc): Make
	non-static.  Drop "diagnostic" param in favor of storing the
	original value of "where" and re-using it.
	(virt_loc_aware_diagnostic_finalizer): Update for dropped param of
	maybe_unwind_expanded_macro_loc.
	(tree_diagnostics_defaults): Initialize context->print_path and
	context->make_json_for_path.
	* tree-diagnostic.h (default_tree_diagnostic_path_printer): New
	decl.
	(default_tree_make_json_for_path): New decl.
	(maybe_unwind_expanded_macro_loc): New decl.

gcc/c-family/ChangeLog:
	* c-format.c (local_event_ptr_node): New.
	(PP_FORMAT_CHAR_TABLE): Add entry for "%@".
	(init_dynamic_diag_info): Initialize local_event_ptr_node.
	* c-format.h (T_EVENT_PTR): New define.

gcc/testsuite/ChangeLog:
	* gcc.dg/format/gcc_diag-10.c (diagnostic_event_id_t): New
	typedef.
	(test_diag): Add coverage of "%@".
	* gcc.dg/plugin/diagnostic-path-format-default.c: New test.
	* gcc.dg/plugin/diagnostic-path-format-inline-events-1.c: New test.
	* gcc.dg/plugin/diagnostic-path-format-inline-events-2.c: New test.
	* gcc.dg/plugin/diagnostic-path-format-inline-events-3.c: New test.
	* gcc.dg/plugin/diagnostic-path-format-none.c: New test.
	* gcc.dg/plugin/diagnostic-test-paths-1.c: New test.
	* gcc.dg/plugin/diagnostic-test-paths-2.c: New test.
	* gcc.dg/plugin/diagnostic-test-paths-3.c: New test.
	* gcc.dg/plugin/diagnostic-test-paths-4.c: New test.
	* gcc.dg/plugin/diagnostic_plugin_test_paths.c: New.
	* gcc.dg/plugin/plugin.exp: Add the new plugin and test cases.

libcpp/ChangeLog:
	* include/line-map.h (class diagnostic_path): New forward decl.
	(rich_location::get_path): New accessor.
	(rich_location::set_path): New function.
	(rich_location::m_path): New field.
	* line-map.c (rich_location::rich_location): Initialize m_path.

From-SVN: r280142

1 files changed, 126 insertions, 0 deletions

diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index 1ab420c..72afd7c 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "diagnostic-color.h"
 #include "diagnostic-url.h"
 #include "diagnostic-metadata.h"
+#include "diagnostic-path.h"
 #include "edit-context.h"
 #include "selftest.h"
 #include "selftest-diagnostic.h"
@@ -187,6 +188,8 @@ diagnostic_initialize (diagnostic_context *context, int n_opts)
   for (i = 0; i < rich_location::STATICALLY_ALLOCATED_RANGES; i++)
     context->caret_chars[i] = '^';
   context->show_cwe = false;
+  context->path_format = DPF_NONE;
+  context->show_path_depths = false;
   context->show_option_requested = false;
   context->abort_on_error = false;
   context->show_column = false;
@@ -658,6 +661,38 @@ diagnostic_report_current_module (diagnostic_context *context, location_t where)
     }
 }
 
+/* If DIAGNOSTIC has a diagnostic_path and CONTEXT supports printing paths,
+   print the path.  */
+
+void
+diagnostic_show_any_path (diagnostic_context *context,
+			  diagnostic_info *diagnostic)
+{
+  const diagnostic_path *path = diagnostic->richloc->get_path ();
+  if (!path)
+    return;
+
+  if (context->print_path)
+    context->print_path (context, path);
+}
+
+/* Return true if the events in this path involve more than one
+   function, or false if it is purely intraprocedural.  */
+
+bool
+diagnostic_path::interprocedural_p () const
+{
+  const unsigned num = num_events ();
+  for (unsigned i = 0; i < num; i++)
+    {
+      if (get_event (i).get_fndecl () != get_event (0).get_fndecl ())
+	return true;
+      if (get_event (i).get_stack_depth () != get_event (0).get_stack_depth ())
+	return true;
+    }
+  return false;
+}
+
 void
 default_diagnostic_starter (diagnostic_context *context,
 			    diagnostic_info *diagnostic)
@@ -1123,6 +1158,8 @@ diagnostic_report_diagnostic (diagnostic_context *context,
 
   context->lock--;
 
+  diagnostic_show_any_path (context, diagnostic);
+
   return true;
 }
 
@@ -1758,6 +1795,95 @@ auto_diagnostic_group::~auto_diagnostic_group ()
     }
 }
 
+/* Implementation of diagnostic_path::num_events vfunc for
+   simple_diagnostic_path: simply get the number of events in the vec.  */
+
+unsigned
+simple_diagnostic_path::num_events () const
+{
+  return m_events.length ();
+}
+
+/* Implementation of diagnostic_path::get_event vfunc for
+   simple_diagnostic_path: simply return the event in the vec.  */
+
+const diagnostic_event &
+simple_diagnostic_path::get_event (int idx) const
+{
+  return *m_events[idx];
+}
+
+/* Add an event to this path at LOC within function FNDECL at
+   stack depth DEPTH.
+
+   Use m_context's printer to format FMT, as the text of the new
+   event.
+
+   Return the id of the new event.  */
+
+diagnostic_event_id_t
+simple_diagnostic_path::add_event (location_t loc, tree fndecl, int depth,
+				   const char *fmt, ...)
+{
+  pretty_printer *pp = m_event_pp;
+  pp_clear_output_area (pp);
+
+  text_info ti;
+  rich_location rich_loc (line_table, UNKNOWN_LOCATION);
+
+  va_list ap;
+
+  va_start (ap, fmt);
+
+  ti.format_spec = _(fmt);
+  ti.args_ptr = &ap;
+  ti.err_no = 0;
+  ti.x_data = NULL;
+  ti.m_richloc = &rich_loc;
+
+  pp_format (pp, &ti);
+  pp_output_formatted_text (pp);
+
+  va_end (ap);
+
+  simple_diagnostic_event *new_event
+    = new simple_diagnostic_event (loc, fndecl, depth, pp_formatted_text (pp));
+  m_events.safe_push (new_event);
+
+  pp_clear_output_area (pp);
+
+  return diagnostic_event_id_t (m_events.length () - 1);
+}
+
+/* struct simple_diagnostic_event.  */
+
+/* simple_diagnostic_event's ctor.  */
+
+simple_diagnostic_event::simple_diagnostic_event (location_t loc,
+						  tree fndecl,
+						  int depth,
+						  const char *desc)
+: m_loc (loc), m_fndecl (fndecl), m_depth (depth), m_desc (xstrdup (desc))
+{
+}
+
+/* simple_diagnostic_event's dtor.  */
+
+simple_diagnostic_event::~simple_diagnostic_event ()
+{
+  free (m_desc);
+}
+
+/* Print PATH by emitting a dummy "note" associated with it.  */
+
+DEBUG_FUNCTION
+void debug (diagnostic_path *path)
+{
+  rich_location richloc (line_table, UNKNOWN_LOCATION);
+  richloc.set_path (path);
+  inform (&richloc, "debug path");
+}
+
 /* Really call the system 'abort'.  This has to go right at the end of
    this file, so that there are no functions after it that call abort
    and get the system abort instead of our macro.  */