Hi.

As shown in the PR, remove_prefix function is written wrongly. It does not distinguish
in between a node in linked list and pprefix->plist. So I decide to rewrite it.
Apart from that, I identified discrepancy in between do_add_prefix and prefix_from_string
where the later one appends always DIR_SEPARATOR (if missing). So I also the former function.
And I'm adding unit tests for all functions in file-find.c.

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin

gcc/ChangeLog:

2017-08-14  Martin Liska  <mliska@suse.cz>

	PR driver/81829
	* file-find.c (do_add_prefix): Always append DIR_SEPARATOR
	at the end of a prefix.
	(remove_prefix): Properly remove elements and accept also
	path without a trailing DIR_SEPARATOR.
	(purge): New function.
	(file_find_verify_prefix_creation): Likewise.
	(file_find_verify_prefix_add): Likewise.
	(file_find_verify_prefix_removal): Likewise.
	(file_find_c_tests): Likewise.
	* selftest-run-tests.c (selftest::run_tests): Add new
	file_find_c_tests.
	* selftest.h (file_find_c_tests): Likewise.
---
 gcc/file-find.c          | 182 ++++++++++++++++++++++++++++++++++++++++++-----
 gcc/selftest-run-tests.c |   1 +
 gcc/selftest.h           |   1 +
 3 files changed, 167 insertions(+), 17 deletions(-)