head r354975 and/or later broke ci.freebsd.org's FreeBSD-head-amd64-gcc builds in tests/sys/sys/bitstring_test.c 's atfu_bit_ffs_area_body

#12250 (of r355014) gots the likes of:

20:48:53 
--- all_subdir_tests/sys/sys ---

20:48:53 
/workspace/src/tests/sys/sys/bitstring_test.c: In function 'atfu_bit_ffc_area_body':

20:48:53 
/workspace/src/sys/sys/bitstring.h:205:5: error: assuming signed overflow does not occur when assuming that (X + c) < X is always false [-Werror=strict-overflow]

20:48:53 
  if (_start >= _nbits) {

20:48:53 
     ^

(I'll not list all the similar errors.)



The first breakage (later changed by lwhsu) was for #12238 (of r354977)
and was different:

21:21:52 
--- all_subdir_tests/sys/sys ---

21:21:52 
/workspace/src/tests/sys/sys/bitstring_test.c: In function 'atfu_bit_ffs_area_body':

21:21:52 
/workspace/src/tests/sys/sys/bitstring_test.c:350:2: error: variable-sized object may not be initialized

21:21:52 
  bitstr_t bit_decl(bitstr, nbits) = {};

21:21:52 
  ^~~~~~~~

21:21:52 
/workspace/src/tests/sys/sys/bitstring_test.c: In function 'atfu_bit_ffc_area_body':

21:21:52 
/workspace/src/tests/sys/sys/bitstring_test.c:419:2: error: variable-sized object may not be initialized

21:21:52 
  bitstr_t bit_decl(bitstr, nbits) = {};

21:21:52 
  ^~~~~~~~

21:21:52 
*** [bitstring_test.o] Error code 1


But, as of when I looked, none of the FreeBSD-head-amd64-gcc build attempts have
completed since then.


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)