c: Fix up cfun->function_end_locus from the C FE [PR94029]

On the following testcase we ICE because while
      DECL_STRUCT_FUNCTION (current_function_decl)->function_start_locus
        = c_parser_peek_token (parser)->location;
and similarly DECL_SOURCE_LOCATION (fndecl) is set from some token's
location, the end is set as:
  /* Store the end of the function, so that we get good line number
     info for the epilogue.  */
  cfun->function_end_locus = input_location;
and the thing is that input_location is only very rarely set in the C FE
(the primary spot that changes it is the cb_line_change/fe_file_change).
Which means, e.g. for pretty much all C functions that are on a single line,
function_start_locus column is > than function_end_locus column, and the
testcase even has smaller line in function_end_locus because cb_line_change
isn't performed while parsing multi-line arguments of a function-like macro.

Attached are two possible fixes to achieve what the C++ FE does, in
particular that cfun->function_end_locus is the locus of the closing } of
the function.  The first one updates input_location when we see a closing }
of a compound statement (though any, not just the function body) and thus
input_location in the finish_function call is what we need.
The second instead propagates the location_t from the parsing of the
outermost compound statement (the function body) to finish_function.
The second one is this version.

2020-03-19  Jakub Jelinek  <jakub@redhat.com>

	PR gcov-profile/94029
	* c-tree.h (finish_function): Add location_t argument defaulted to
	input_location.
	* c-parser.c (c_parser_compound_statement): Add endlocp argument and
	set it to the locus of closing } if non-NULL.
	(c_parser_compound_statement_nostart): Return locus of closing }.
	(c_parser_parse_rtl_body): Likewise.
	(c_parser_declaration_or_fndef): Propagate locus of closing } to
	finish_function.
	* c-decl.c (finish_function): Add end_loc argument, use it instead of
	input_location to set function_end_locus.

	* gcc.misc-tests/gcov-pr94029.c: New test.

1 files changed, 14 insertions, 0 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 25f8f5b..c0b65a5 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,17 @@
+2020-03-19  Jakub Jelinek  <jakub@redhat.com>
+
+	PR gcov-profile/94029
+	* c-tree.h (finish_function): Add location_t argument defaulted to
+	input_location.
+	* c-parser.c (c_parser_compound_statement): Add endlocp argument and
+	set it to the locus of closing } if non-NULL.
+	(c_parser_compound_statement_nostart): Return locus of closing }.
+	(c_parser_parse_rtl_body): Likewise.
+	(c_parser_declaration_or_fndef): Propagate locus of closing } to
+	finish_function.
+	* c-decl.c (finish_function): Add end_loc argument, use it instead of
+	input_location to set function_end_locus.
+
 2020-03-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/94172