input.c/libcpp: fix lifetimes of path buffers

input.c/libcpp: fix lifetimes of path buffers

Running "make selftest-valgrind" showed various leaks of the form:

408 bytes in 24 blocks are definitely lost in loss record 572 of 679
   at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x1B0D057: xmalloc (xmalloc.c:148)
   by 0x1ACCAA1: append_file_to_dir(char const*, cpp_dir*) [clone .isra.3] (files.c:1567)
   by 0x1ACD56F: _cpp_find_file (files.c:390)
   by 0x1ACF8FB: cpp_read_main_file(cpp_reader*, char const*) (init.c:632)
   by 0x1AB3D97: selftest::lexer_test::lexer_test(selftest::line_table_case const&, char const*, selftest::lexer_test_options*) (input.c:2014)
   by 0x1AB792B: selftest::test_lexer_string_locations_u8(selftest::line_table_case const&) (input.c:2713)
   by 0x1ABA22A: selftest::for_each_line_table_case(void (*)(selftest::line_table_case const&)) (input.c:3227)
   by 0x1ABA381: selftest::input_c_tests() (input.c:3260)
   by 0x1A295F1: selftest::run_tests() (selftest-run-tests.c:62)
   by 0xF20DC4: toplev::run_self_tests() (toplev.c:2076)
   by 0xF20FCD: toplev::main(int, char**) (toplev.c:2153)

Fix the leak by freeing the file->path in destroy_cpp_file.
However, doing so would lead to a use-after-free in input.c's file cache
since the filenames in this cache are the libcpp file->path buffers.

Hence we need to ensure that any references to the file in the input.c
cache are purged before cleaning up file->path.  This is normally done
by the temp_source_file dtor.  Hence we need to reorder things to that
the temp_source_file dtor runs before cleaning up the cpp_parser.  The
patch does this by introducing a wrapper class around cpp_parser *, so
that the dtor can run after the dtor for temp_source_file.

gcc/ChangeLog:
	* input.c (fcache::file_patch): Add comment about lifetime.
	(selftest::cpp_reader_ptr): New class.
	(selftest::lexer_test): Convert m_parser from cpp_reader *
	to a cpp_reader_ptr, and move m_tempfile to after it.
	(selftest::lexer_test::lexer_test): Update for above reordering.
	(lexer_test::~lexer_test): Move cleanup of m_parser to
	cpp_reader_ptr's dtor.

libcpp/ChangeLog:
	* files.c (destroy_cpp_file): Free file->path.

From-SVN: r241536