This is v6 of the patch, as posted to:
  https://gcc.gnu.org/ml/gcc-patches/2018-12/msg01331.html


The C++ frontend gained various location wrapper nodes in r256448 (GCC 8).
That patch:
  https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00799.html
added wrapper nodes around all nodes with !CAN_HAVE_LOCATION_P for:

* arguments at callsites, and for

* typeid, alignof, sizeof, and offsetof.

This is a followup to that patch, adding many more location wrappers
to the C++ frontend.  It adds location wrappers for nodes with
!CAN_HAVE_LOCATION_P to:

* all literal nodes (in cp_parser_primary_expression)

* all id-expression nodes (in finish_id_expression), except within a
  decltype.

* all mem-initializer nodes within a mem-initializer-list
  (in cp_parser_mem_initializer)

However, the patch also adds some suppressions: regions in the parser
for which wrapper nodes will not be created:

* within a template-parameter-list or template-argument-list (in
  cp_parser_template_parameter_list and cp_parser_template_argument_list
  respectively), to avoid encoding the spelling location of the nodes
  in types.  For example, "array<10>" and "array<10>" are the same type,
  despite the fact that the two different "10" tokens are spelled in
  different locations in the source.

* within a gnu-style attribute (none of are handlers are set up to cope
  with location wrappers yet)

* within various OpenMP clauses

The patch enables various improvements to locations for bad
initializations, for -Wchar-subscripts, and enables various other
improvements in the followup patch.

For example, given the followup buggy mem-initializer:

class X {
  X() : bad(42),
        good(42)
  { }
  void* bad;
  int good;
};

previously, our diagnostic was on the final close parenthesis of the
mem-initializer-list, leaving it unclear where the problem is:

t.cc: In constructor 'X::X()':
t.cc:3:16: error: invalid conversion from 'int' to 'void*' [-fpermissive]
    3 |         good(42)
      |                ^
      |                |
      |                int

whereas with the patch we highlight which expression is bogus:

t.cc: In constructor 'X::X()':
t.cc:2:13: error: invalid conversion from 'int' to 'void*' [-fpermissive]
    2 |   X() : bad(42),
      |             ^~
      |             |
      |             int

Similarly, the diagnostic for this bogus initialization:

i.cc:1:44: error: initializer-string for array of chars is too long [-fpermissive]
    1 | char test[3][4] = { "ok", "too long", "ok" };
      |                                            ^

is improved by the patch so that it indicates which string is too long:

i.cc:1:27: error: initializer-string for array of chars is too long [-fpermissive]
    1 | char test[3][4] = { "ok", "too long", "ok" };
      |                           ^~~~~~~~~~


gcc/c-family/ChangeLog:
	PR c++/43064
	PR c++/43486
	* c-common.c (unsafe_conversion_p): Fold any location wrapper.
	(verify_tree): Handle location wrappers.
	(c_common_truthvalue_conversion): Strip any location wrapper.
	Handle CONST_DECL.
	(fold_offsetof): Strip any location wrapper.
	(complete_array_type): Likewise for initial_value.
	(convert_vector_to_array_for_subscript): Call fold_for_warn on the
	index before checking for INTEGER_CST.
	* c-pretty-print.c (c_pretty_printer::primary_expression): Don't
	print parentheses around location wrappers.
	* c-warn.c (warn_logical_operator): Call fold_for_warn on op_right
	before checking for INTEGER_CST.
	(warn_tautological_bitwise_comparison): Call
	tree_strip_any_location_wrapper on lhs, rhs, and bitop's operand
	before checking for INTEGER_CST.
	(readonly_error): Strip any location wrapper.
	(warn_array_subscript_with_type_char): Strip location wrappers
	before checking for INTEGER_CST.  Use the location of the index if
	available.

gcc/ChangeLog:
	PR c++/43064
	PR c++/43486
	* convert.c: Include "selftest.h".
	(preserve_any_location_wrapper): New function.
	(convert_to_pointer_maybe_fold): Update to handle location
	wrappers.
	(convert_to_real_maybe_fold): Likewise.
	(convert_to_integer_1): Strip expr when using TREE_OVERFLOW.
	Handle location wrappers when checking for INTEGER_CST.
	(convert_to_integer_maybe_fold): Update to handle location
	wrappers.
	(convert_to_complex_maybe_fold): Likewise.
	(selftest::test_convert_to_integer_maybe_fold): New functions.
	(selftest::convert_c_tests): New function.
	* convert.h (preserve_any_location_wrapper): New decl.
	* fold-const.c (size_binop_loc): Strip location wrappers when
	using TREE_OVERFLOW.
	(operand_equal_p): Strip any location wrappers.
	(integer_valued_real_p): Strip any location wrapper.
	* selftest-run-tests.c (selftest::run_tests): Call
	selftest::convert_c_tests.
	* selftest.h (selftest::convert_c_tests): New decl.
	* tree.c (build_complex): Assert that REAL and IMAG are constants.
	(integer_zerop): Look through location wrappers.
	(integer_onep): Likewise.
	(integer_each_onep): Likewise.
	(integer_all_onesp): Likewise.
	(integer_minus_onep): Likewise.
	(integer_pow2p): Likewise.
	(integer_nonzerop): Likewise.
	(integer_truep): Likewise.
	(fixed_zerop): Likewise.
	(real_zerop): Likewise.
	(real_onep): Likewise.
	(real_minus_onep): Likewise.
	(tree_int_cst_equal): Likewise.
	(simple_cst_equal): Treat location wrappers with non-equal source
	locations as being unequal.
	(uniform_integer_cst_p): Look through location wrappers.
	(maybe_wrap_with_location): Don't create wrappers if any
	auto_suppress_location_wrappers are active.
	(suppress_location_wrappers): New variable.
	(selftest::test_predicates): New test.
	(selftest::tree_c_tests): Call it.
	* tree.h (CONSTANT_CLASS_OR_WRAPPER_P): New macro.
	(suppress_location_wrappers): New decl.
	(class auto_suppress_location_wrappers): New class.

gcc/cp/ChangeLog:
	PR c++/43064
	PR c++/43486
	* call.c (build_conditional_expr_1): Strip location wrappers when
	checking for CONST_DECL.
	(conversion_null_warnings): Use location of "expr" if available.
	* class.c (fixed_type_or_null): Handle location wrappers.
	* constexpr.c (potential_constant_expression_1): Likewise.
	* cvt.c (ignore_overflows): Strip location wrappers when
	checking for INTEGER_CST, and re-wrap the result if present.
	(ocp_convert): Call fold_for_warn before checking for INTEGER_CST.
	* decl.c (reshape_init_r): Strip any location wrapper.
	(undeduced_auto_decl): Likewise.
	* expr.c (mark_discarded_use): Likewise for expr.
	* init.c (build_aggr_init): Likewise before checking init for
	DECL_P.
	(warn_placement_new_too_small): Call fold_for_warn on adj before
	checking for CONSTANT_CLASS_P, and on nelts.  Strip any location
	wrapper from op0 and on oper before checking for VAR_P.
	* parser.c (cp_parser_primary_expression): Call
	maybe_add_location_wrapper on numeric and string literals.
	(cp_parser_postfix_expression): Strip any location wrapper when
	checking for DECL_IS_BUILTIN_CONSTANT_P.
	(cp_parser_unary_expression): Ensure that folding of NEGATE_EXPR
	around a constant happens in the presence of location wrappers and
	returns a wrapped result.
	(cp_parser_has_attribute_expression): Strip any location wrapper
	from "oper".
	(cp_parser_binary_expression): Strip any location wrapper when
	checking for DECL_P on the lhs.
	(cp_parser_decltype): Strip any location wrapper from result of
	cp_parser_decltype_expr.
	(cp_parser_mem_initializer): Add location wrappers to the
	parenthesized expression list.
	(cp_parser_template_parameter_list): Don't create wrapper nodes
	within a template-parameter-list.
	(cp_parser_template_argument_list): Don't create wrapper nodes
	within a template-argument-list.
	(cp_parser_parameter_declaration): Strip location wrappers from
	default arguments.
	(cp_parser_gnu_attribute_list): Don't create wrapper nodes.
	(cp_parser_std_attribute_spec_seq): Likewise.
	(cp_parser_omp_all_clauses): Don't create wrapper nodes within
	OpenMP clauses.
	(cp_parser_omp_for_loop): Likewise.
	(cp_parser_omp_declare_reduction_exprs): Likewise.
	* pt.c (convert_nontype_argument_function): Strip location
	wrappers from fn_no_ptr before checking for FUNCTION_DECL.
	(tsubst_default_argument): Move note about which callsite led to
	instantiation to after the check_default_argument call.
	(do_auto_deduction): Likewise from init before checking for
	DECL_P.
	* semantics.c (force_paren_expr): Likewise from expr before
	checking for DECL_P.
	(finish_parenthesized_expr): Likewise from expr before
	checking for STRING_CST.
	(perform_koenig_lookup): Likewise from fn.
	(finish_call_expr): Likewise.
	(finish_id_expression): Rename to...
	(finish_id_expression_1): ...this, calling
	maybe_add_location_wrapper on the result.
	(capture_decltype): Use lookup_name_real rather than value_member
	when looking up decl within the capture-list.
	* tree.c (cp_stabilize_reference): Strip any location wrapper.
	(builtin_valid_in_constant_expr_p): Likewise.
	(strip_typedefs_expr): Strip any location wrapper before checking
	for decls or constants.
	(is_overloaded_fn): Likewise.
	(maybe_get_fns): Likewise.
	(selftest::test_lvalue_kind): Verify lvalue_p.
	* typeck.c (cxx_sizeof_expr): Strip any location wrapper.
	(cxx_alignof_expr): Likewise.
	(is_bitfield_expr_with_lowered_type): Handle location wrappers.
	(cp_build_array_ref): Call maybe_constant_value on "idx".
	(cp_build_binary_op): Strip location wrapper from first_arg before
	checking for PARM_DECL.  Likewise for op1 before checking for
	INTEGER_CST in two places.  Likewise for orig_op0 and orig_op1
	when checking for STRING_CST.
	(cp_build_addr_expr_1): Likewise for arg when checking for
	FUNCTION_DECL.
	(cp_build_modify_expr): Likewise for newrhs when checking for
	STRING_CST.
	(convert_for_assignment): Don't strip location wrappers when
	stripping NON_LVALUE_EXPR.
	(maybe_warn_about_returning_address_of_local): Strip location
	wrapper from whats_returned before checking for DECL_P.
	(can_do_nrvo_p): Strip location wrapper from retval.
	(treat_lvalue_as_rvalue_p): Likewise.
	(check_return_expr): Likewise.
	* typeck2.c (cxx_incomplete_type_diagnostic): Strip location
	wrapper from value before checking for VAR_P or PARM_DECL.
	(digest_init_r): Strip location wrapper from init.  When
	copying "init", also copy the wrapped node.

gcc/objc/ChangeLog:
	PR c++/43064
	PR c++/43486
	* objc-act.c (objc_maybe_build_component_ref): Strip any location
	wrapper before checking for UOBJC_SUPER_decl and self_decl.
	(objc_finish_message_expr): Strip any location wrapper.
	(gen_declaration): Strip location wrappers from "w".

gcc/testsuite/ChangeLog:
	PR c++/43064
	PR c++/43486
	* c-c++-common/pr51712.c (valid2): Mark xfail as passing on C++.
	* g++.dg/cpp0x/constexpr-47969.C: Update column of expected error.
	* g++.dg/cpp0x/constexpr-ex2.C: Likewise.
	* g++.dg/cpp0x/scoped_enum2.C: Likewise.
	* g++.dg/cpp1z/decomp48.C: Update expected location of warning
	for named local variables to use that of the local variable.
	* g++.dg/ext/vla1.C: Update column.
	* g++.dg/init/array43.C: Update expected column to be that of the
	initializer.
	* g++.dg/init/initializer-string-too-long.C: New test.
	* g++.dg/init/new44.C: Add "-ftrack-macro-expansion=0".
	* g++.dg/init/pr43064-1.C: New test.
	* g++.dg/init/pr43064-2.C: New test.
	* g++.dg/init/pr43064-3.C: New test.
	* g++.dg/other/fold1.C: Update column of expected error.
	* g++.dg/parse/crash36.C: Likewise.
	* g++.dg/plugin/diagnostic-test-expressions-1.C: Add negative
	integer and float expressions.
	* g++.dg/template/defarg6.C: Move expected error to the default
	argument; add expected message about where instantiated.
	* g++.dg/wrappers/Wparentheses.C: New test.
	* g++.old-deja/g++.bugs/900402_02.C: Update column of expected
	error.

From-SVN: r267272