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, 149 insertions, 0 deletions

diff --git a/gcc/diagnostic-path.h b/gcc/diagnostic-path.h
new file mode 100644
index 00000000000..d005da351a7
--- /dev/null
+++ b/gcc/diagnostic-path.h
@@ -0,0 +1,149 @@
+/* Paths through the code associated with a diagnostic.
+   Copyright (C) 2019-2020 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_DIAGNOSTIC_PATH_H
+#define GCC_DIAGNOSTIC_PATH_H
+
+#include "diagnostic.h" /* for ATTRIBUTE_GCC_DIAG.  */
+#include "diagnostic-event-id.h"
+
+/* A diagnostic_path is an optional additional piece of metadata associated
+   with a diagnostic (via its rich_location).
+
+   It describes a sequence of events predicted by the compiler that
+   lead to the problem occurring, with their locations in the user's source,
+   and text descriptions.
+
+   For example, the following error has a 3-event 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 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.  */
+
+/* Abstract base classes, describing events within a path, and the paths
+   themselves.  */
+
+/* One event within a diagnostic_path.  */
+
+class diagnostic_event
+{
+ public:
+  virtual ~diagnostic_event () {}
+
+  virtual location_t get_location () const = 0;
+
+  virtual tree get_fndecl () const = 0;
+
+  /* Stack depth, so that consumers can visualizes the interprocedural
+     calls, returns, and frame nesting.  */
+  virtual int get_stack_depth () const = 0;
+
+  /* Get a localized (and possibly colorized) description of this event.  */
+  virtual label_text get_desc (bool can_colorize) const = 0;
+};
+
+/* Abstract base class for getting at a sequence of events.  */
+
+class diagnostic_path
+{
+ public:
+  virtual ~diagnostic_path () {}
+  virtual unsigned num_events () const = 0;
+  virtual const diagnostic_event & get_event (int idx) const = 0;
+
+  bool interprocedural_p () const;
+};
+
+/* Concrete subclasses.  */
+
+/* A simple implementation of diagnostic_event.  */
+
+class simple_diagnostic_event : public diagnostic_event
+{
+ public:
+  simple_diagnostic_event (location_t loc, tree fndecl, int depth,
+			   const char *desc);
+  ~simple_diagnostic_event ();
+
+  location_t get_location () const FINAL OVERRIDE { return m_loc; }
+  tree get_fndecl () const FINAL OVERRIDE { return m_fndecl; }
+  int get_stack_depth () const FINAL OVERRIDE { return m_depth; }
+  label_text get_desc (bool) const FINAL OVERRIDE
+  {
+    return label_text::borrow (m_desc);
+  }
+
+ private:
+  location_t m_loc;
+  tree m_fndecl;
+  int m_depth;
+  char *m_desc; // has been i18n-ed and formatted
+};
+
+/* A simple implementation of diagnostic_path, as a vector of
+   simple_diagnostic_event instances.  */
+
+class simple_diagnostic_path : public diagnostic_path
+{
+ public:
+  simple_diagnostic_path (pretty_printer *event_pp)
+  : m_event_pp (event_pp) {}
+
+  unsigned num_events () const FINAL OVERRIDE;
+  const diagnostic_event & get_event (int idx) const FINAL OVERRIDE;
+
+  diagnostic_event_id_t add_event (location_t loc, tree fndecl, int depth,
+				   const char *fmt, ...)
+    ATTRIBUTE_GCC_DIAG(5,6);
+
+ private:
+  auto_delete_vec<simple_diagnostic_event> m_events;
+
+  /* (for use by add_event).  */
+  pretty_printer *m_event_pp;
+};
+
+extern void debug (diagnostic_path *path);
+
+#endif /* ! GCC_DIAGNOSTIC_PATH_H */