lib/libc/tests/string: add unit tests for ffs, ffsl, ffsll, fls, flsl, and flsll

[fuz]

Summary

Add atf unit tests for ffs, ffsl, ffsll, fls, flsl, flsll.
These unit tests will be used for an upcoming DR.

Also supply CFLAGS+=-fno-builtin to ensure our unit tests
actually test libc functions and not clang's builtins.

Sponsored by: FreeBSD Foundation

Test Plan

Unit tests pass with current implementations of
these functions. This DR is the test plan for an upcoming DR.

[kevans]

This seems to LGTM, let's perhaps pull in ngie for another sanity check. I think templating ffs_test and fls_test like this is a fine approach.

[ngie]

Are these testcases already implemented in the libm tests?

[ngie]

lib/libc/tests/string/flsll_test.c

29–31

Why don't you just modify the CFLAGS to define these things at build time instead of creating a ton of basically boilerplate C files?

[fuz]

This seems to LGTM, let's perhaps pull in ngie for another sanity check. I think templating ffs_test and fls_test like this is a fine approach.

Thanks. Do I have approval to commit once @ngie approves? If yes, can this be MFC'ed to 13-STABLE?

Are these testcases already implemented in the libm tests?

I am not aware of any such tests.

lib/libc/tests/string/flsll_test.c

29–31

I was copying the design pattern used for string functions. If this is not how I am supposed to write test cases, could you point me at some example I can copy?

[mjg]

I don't think these should run by default, in fact the overall suite is already taking way too long

can this be made condiitonal, even if installed