bitstring: Support large bit strings.

Replace int with either size_t or ssize_t (depending on context) in
order to support bit strings up to SSIZE_MAX bits in length.  Since
some of the arguments that need to change type are pointers, we must
resort to light preprocessor trickery to avoid breaking existing code.

MFC after:	3 weeks
Sponsored by:	Klara, Inc.
Reviewed by:	kevans
Differential Revision:	https://reviews.freebsd.org/D42698

(cherry picked from commit c56f45f2a9da7d989b79fd6c34b63100609ff9ae)

3 files changed, 181 insertions, 117 deletions

diff --git a/share/man/man3/bitstring.3 b/share/man/man3/bitstring.3
index ac87ac6d9124..808cd48f384b 100644
--- a/share/man/man3/bitstring.3
+++ b/share/man/man3/bitstring.3
@@ -57,7 +57,7 @@
 .\"
 .\"     @(#)bitstring.3	8.1 (Berkeley) 7/19/93
 .\"
-.Dd August 8, 2021
+.Dd November 21, 2023
 .Dt BITSTRING 3
 .Os
 .Sh NAME
@@ -85,49 +85,49 @@
 .Sh SYNOPSIS
 .In bitstring.h
 .Ft bitstr_t *
-.Fn bit_alloc "int nbits"
+.Fn bit_alloc "size_t nbits"
 .Ft void
-.Fn bit_decl "bitstr_t *name" "int nbits"
+.Fn bit_decl "bitstr_t *name" "size_t nbits"
 .Ft void
-.Fn bit_clear "bitstr_t *name" "int bit"
+.Fn bit_clear "bitstr_t *name" "size_t bit"
 .Ft void
-.Fn bit_count "bitstr_t *name" "int count" "int nbits" "int *value"
+.Fn bit_count "bitstr_t *name" "size_t count" "size_t nbits" "ssize_t *value"
 .Ft void
-.Fn bit_ffc "bitstr_t *name" "int nbits" "int *value"
+.Fn bit_ffc "bitstr_t *name" "size_t nbits" "ssize_t *value"
 .Ft void
-.Fn bit_ffs "bitstr_t *name" "int nbits" "int *value"
+.Fn bit_ffs "bitstr_t *name" "size_t nbits" "ssize_t *value"
 .Ft void
-.Fn bit_ffc_at "bitstr_t *name" "int start" "int nbits" "int *value"
+.Fn bit_ffc_at "bitstr_t *name" "size_t start" "size_t nbits" "ssize_t *value"
 .Ft void
-.Fn bit_ffs_at "bitstr_t *name" "int start" "int nbits" "int *value"
+.Fn bit_ffs_at "bitstr_t *name" "size_t start" "size_t nbits" "ssize_t *value"
 .Ft void
-.Fn bit_ff_at "bitstr_t *name" "int start" "int nbits" "int match" "int *value"
+.Fn bit_ff_at "bitstr_t *name" "size_t start" "size_t nbits" "int match" "ssize_t *value"
 .Ft void
-.Fn bit_ffc_area "bitstr_t *name" "int nbits" "int size" "int *value"
+.Fn bit_ffc_area "bitstr_t *name" "size_t nbits" "size_t size" "ssize_t *value"
 .Ft void
-.Fn bit_ffs_area "bitstr_t *name" "int nbits" "int size" "int *value"
+.Fn bit_ffs_area "bitstr_t *name" "size_t nbits" "size_t size" "ssize_t *value"
 .Ft void
-.Fn bit_ffc_area_at "bitstr_t *name" "int start" "int nbits" "int size" "int *value"
+.Fn bit_ffc_area_at "bitstr_t *name" "size_t start" "size_t nbits" "size_t size" "ssize_t *value"
 .Ft void
-.Fn bit_ffs_area_at "bitstr_t *name" "int start" "int nbits" "int size" "int *value"
+.Fn bit_ffs_area_at "bitstr_t *name" "size_t start" "size_t nbits" "size_t size" "ssize_t *value"
 .Ft void
-.Fn bit_ff_area_at "bitstr_t *name" "int start" "int nbits" "int size" "int match" "int *value"
-.Fn bit_foreach "bitstr_t *name" "int nbits" "int var"
-.Fn bit_foreach_at "bitstr_t *name" "int start" "int nbits" "int var"
-.Fn bit_foreach_unset "bitstr_t *name" "int nbits" "int var"
-.Fn bit_foreach_unset_at "bitstr_t *name" "int start" "int nbits" "int var"
+.Fn bit_ff_area_at "bitstr_t *name" "size_t start" "size_t nbits" "size_t size" "int match" "ssize_t *value"
+.Fn bit_foreach "bitstr_t *name" "size_t nbits" "size_t var"
+.Fn bit_foreach_at "bitstr_t *name" "size_t start" "size_t nbits" "size_t var"
+.Fn bit_foreach_unset "bitstr_t *name" "size_t nbits" "size_t var"
+.Fn bit_foreach_unset_at "bitstr_t *name" "size_t start" "size_t nbits" "size_t var"
 .Ft void
-.Fn bit_nclear "bitstr_t *name" "int start" "int stop"
+.Fn bit_nclear "bitstr_t *name" "size_t start" "size_t stop"
 .Ft void
-.Fn bit_nset "bitstr_t *name" "int start" "int stop"
+.Fn bit_nset "bitstr_t *name" "size_t start" "size_t stop"
 .Ft int
-.Fn bit_ntest "bitstr_t *name" "int start" "int stop" "int match"
+.Fn bit_ntest "bitstr_t *name" "size_t start" "size_t stop" "int match"
 .Ft void
-.Fn bit_set "bitstr_t *name" "int bit"
+.Fn bit_set "bitstr_t *name" "size_t bit"
 .Ft int
-.Fn bitstr_size "int nbits"
+.Fn bitstr_size "size_t nbits"
 .Ft int
-.Fn bit_test "bitstr_t *name" "int bit"
+.Fn bit_test "bitstr_t *name" "size_t bit"
 .Sh DESCRIPTION
 These macros operate on strings of bits.
 .Pp
diff --git a/sys/sys/bitstring.h b/sys/sys/bitstring.h
index 127de2ebc419..8a976962dd36 100644
--- a/sys/sys/bitstring.h
+++ b/sys/sys/bitstring.h
@@ -75,35 +75,33 @@ typedef	unsigned long bitstr_t;
 #define	_BITSTR_MASK (~0UL)
 #define	_BITSTR_BITS (sizeof(bitstr_t) * 8)
 
-#ifdef roundup2
-#define        _bit_roundup2 roundup2
-#else
-#define        _bit_roundup2(x, y)        (((x)+((y)-1))&(~((y)-1))) /* if y is powers of two */
-#endif
+/* round up x to the next multiple of y if y is a power of two */
+#define _bit_roundup2(x, y)						\
+	(((size_t)(x) + (y) - 1) & ~((size_t)(y) - 1))
 
 /* bitstr_t in bit string containing the bit. */
-static inline int
-_bit_idx(int _bit)
+static inline size_t
+_bit_idx(size_t _bit)
 {
 	return (_bit / _BITSTR_BITS);
 }
 
 /* bit number within bitstr_t at _bit_idx(_bit). */
-static inline int
-_bit_offset(int _bit)
+static inline size_t
+_bit_offset(size_t _bit)
 {
 	return (_bit % _BITSTR_BITS);
 }
 
 /* Mask for the bit within its long. */
 static inline bitstr_t
-_bit_mask(int _bit)
+_bit_mask(size_t _bit)
 {
 	return (1UL << _bit_offset(_bit));
 }
 
 static inline bitstr_t
-_bit_make_mask(int _start, int _stop)
+_bit_make_mask(size_t _start, size_t _stop)
 {
 	return ((_BITSTR_MASK << _bit_offset(_start)) &
 	    (_BITSTR_MASK >> (_BITSTR_BITS - _bit_offset(_stop) - 1)));
@@ -111,18 +109,18 @@ _bit_make_mask(int _start, int _stop)
 
 /*----------------------------- Public Interface -----------------------------*/
 /* Number of bytes allocated for a bit string of nbits bits */
-#define	bitstr_size(_nbits) (_bit_roundup2(_nbits, _BITSTR_BITS) / 8)
+#define	bitstr_size(_nbits) (_bit_roundup2((_nbits), _BITSTR_BITS) / 8)
 
 /* Allocate a bit string initialized with no bits set. */
 #ifdef _KERNEL
 static inline bitstr_t *
-bit_alloc(int _nbits, struct malloc_type *type, int flags)
+bit_alloc(size_t _nbits, struct malloc_type *type, int flags)
 {
 	return ((bitstr_t *)malloc(bitstr_size(_nbits), type, flags | M_ZERO));
 }
 #else
 static inline bitstr_t *
-bit_alloc(int _nbits)
+bit_alloc(size_t _nbits)
 {
 	return ((bitstr_t *)calloc(bitstr_size(_nbits), 1));
 }
@@ -134,28 +132,28 @@ bit_alloc(int _nbits)
 
 /* Is bit N of bit string set? */
 static inline int
-bit_test(const bitstr_t *_bitstr, int _bit)
+bit_test(const bitstr_t *_bitstr, size_t _bit)
 {
 	return ((_bitstr[_bit_idx(_bit)] & _bit_mask(_bit)) != 0);
 }
 
 /* Set bit N of bit string. */
 static inline void
-bit_set(bitstr_t *_bitstr, int _bit)
+bit_set(bitstr_t *_bitstr, size_t _bit)
 {
 	_bitstr[_bit_idx(_bit)] |= _bit_mask(_bit);
 }
 
 /* clear bit N of bit string name */
 static inline void
-bit_clear(bitstr_t *_bitstr, int _bit)
+bit_clear(bitstr_t *_bitstr, size_t _bit)
 {
 	_bitstr[_bit_idx(_bit)] &= ~_bit_mask(_bit);
 }
 
 /* Are bits in [start ... stop] in bit string all 0 or all 1? */
 static inline int
-bit_ntest(const bitstr_t *_bitstr, int _start, int _stop, int _match)
+bit_ntest(const bitstr_t *_bitstr, size_t _start, size_t _stop, int _match)
 {
 	const bitstr_t *_stopbitstr;
 	bitstr_t _mask;
@@ -183,7 +181,7 @@ bit_ntest(const bitstr_t *_bitstr, int _start, int _stop, int _match)
 
 /* Set bits start ... stop inclusive in bit string. */
 static inline void
-bit_nset(bitstr_t *_bitstr, int _start, int _stop)
+bit_nset(bitstr_t *_bitstr, size_t _start, size_t _stop)
 {
 	bitstr_t *_stopbitstr;
 
@@ -206,7 +204,7 @@ bit_nset(bitstr_t *_bitstr, int _start, int _stop)
 
 /* Clear bits start ... stop inclusive in bit string. */
 static inline void
-bit_nclear(bitstr_t *_bitstr, int _start, int _stop)
+bit_nclear(bitstr_t *_bitstr, size_t _start, size_t _stop)
 {
 	bitstr_t *_stopbitstr;
 
@@ -228,20 +226,17 @@ bit_nclear(bitstr_t *_bitstr, int _start, int _stop)
 }
 
 /* Find the first '_match'-bit in bit string at or after bit start. */
-static inline void
-bit_ff_at(bitstr_t *_bitstr, int _start, int _nbits, int _match,
-    int *_result)
+static inline ssize_t
+bit_ff_at_(bitstr_t *_bitstr, size_t _start, size_t _nbits, int _match)
 {
 	bitstr_t *_curbitstr;
 	bitstr_t *_stopbitstr;
 	bitstr_t _mask;
 	bitstr_t _test;
-	int _value;
+	ssize_t _value;
 
-	if (_start >= _nbits || _nbits <= 0) {
-		*_result = -1;
-		return;
-	}
+	if (_start >= _nbits || _nbits <= 0)
+		return (-1);
 
 	_curbitstr = _bitstr + _bit_idx(_start);
 	_stopbitstr = _bitstr + _bit_idx(_nbits - 1);
@@ -255,51 +250,40 @@ bit_ff_at(bitstr_t *_bitstr, int _start, int _nbits, int _match,
 
 	_value = ((_curbitstr - _bitstr) * _BITSTR_BITS) + ffsl(_test) - 1;
 	if (_test == 0 ||
-	    (_bit_offset(_nbits) != 0 && _value >= _nbits))
+	    (_bit_offset(_nbits) != 0 && (size_t)_value >= _nbits))
 		_value = -1;
-	*_result = _value;
+	return (_value);
 }
+#define bit_ff_at(_bitstr, _start, _nbits, _match, _resultp)		\
+	*(_resultp) = bit_ff_at_((_bitstr), (_start), (_nbits), (_match))
 
 /* Find the first bit set in bit string at or after bit start. */
-static inline void
-bit_ffs_at(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
-{
-	bit_ff_at(_bitstr, _start, _nbits, 1, _result);
-}
+#define bit_ffs_at(_bitstr, _start, _nbits, _resultp) \
+	*(_resultp) = bit_ff_at_((_bitstr), (_start), (_nbits), 1)
 
 /* Find the first bit clear in bit string at or after bit start. */
-static inline void
-bit_ffc_at(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
-{
-	bit_ff_at(_bitstr, _start, _nbits, 0, _result);
-}
+#define bit_ffc_at(_bitstr, _start, _nbits, _resultp) \
+	*(_resultp) = bit_ff_at_((_bitstr), (_start), (_nbits), 0)
 
 /* Find the first bit set in bit string. */
-static inline void
-bit_ffs(bitstr_t *_bitstr, int _nbits, int *_result)
-{
-	bit_ffs_at(_bitstr, /*start*/0, _nbits, _result);
-}
+#define bit_ffs(_bitstr, _nbits, _resultp) \
+	*(_resultp) = bit_ff_at_((_bitstr), 0, (_nbits), 1)
 
 /* Find the first bit clear in bit string. */
-static inline void
-bit_ffc(bitstr_t *_bitstr, int _nbits, int *_result)
-{
-	bit_ffc_at(_bitstr, /*start*/0, _nbits, _result);
-}
+#define bit_ffc(_bitstr, _nbits, _resultp) \
+	*(_resultp) = bit_ff_at_((_bitstr), 0, (_nbits), 0)
 
 /* Find contiguous sequence of at least size '_match'-bits at or after start */
-static inline void
-bit_ff_area_at(bitstr_t *_bitstr, int _start, int _nbits, int _size,
-    int _match, int *_result)
+static inline ssize_t
+bit_ff_area_at_(bitstr_t *_bitstr, size_t _start, size_t _nbits, size_t _size,
+    int _match)
 {
 	bitstr_t *_curbitstr, _mask, _test;
-	int _value, _last, _shft, _maxshft;
+	size_t _last, _shft, _maxshft;
+	ssize_t _value;
 
-	if (_start + _size > _nbits || _nbits <= 0) {
-		*_result = -1;
-		return;
-	}
+	if (_start + _size > _nbits || _nbits <= 0)
+		return (-1);
 
 	_mask = _match ? _BITSTR_MASK : 0;
 	_maxshft = _bit_idx(_size - 1) == 0 ? _size : (int)_BITSTR_BITS;
@@ -330,48 +314,37 @@ bit_ff_area_at(bitstr_t *_bitstr, int _start, int _nbits, int _size,
 			break;
 		/* A solution here needs bits from the next word. */
 	}
-	*_result = _value;
+	return (_value);
 }
+#define bit_ff_area_at(_bitstr, _start, _nbits, _size, _match, _resultp) \
+	*(_resultp) = bit_ff_area_at_(_bitstr, _start, _nbits, _size, _match);
 
 /* Find contiguous sequence of at least size set bits at or after start */
-static inline void
-bit_ffs_area_at(bitstr_t *_bitstr, int _start, int _nbits, int _size,
-    int *_result)
-{
-	bit_ff_area_at(_bitstr, _start, _nbits, _size, 1, _result);
-}
+#define bit_ffs_area_at(_bitstr, _start, _nbits, _size, _resultp)	\
+	*(_resultp) = bit_ff_area_at_((_bitstr), (_start), (_nbits), (_size), 1)
 
 /* Find contiguous sequence of at least size cleared bits at or after start */
-static inline void
-bit_ffc_area_at(bitstr_t *_bitstr, int _start, int _nbits, int _size,
-    int *_result)
-{
-	bit_ff_area_at(_bitstr, _start, _nbits, _size, 0, _result);
-}
+#define bit_ffc_area_at(_bitstr, _start, _nbits, _size, _resultp)	\
+	*(_resultp) = bit_ff_area_at_((_bitstr), (_start), (_nbits), (_size), 0)
 
 /* Find contiguous sequence of at least size set bits in bit string */
-static inline void
-bit_ffs_area(bitstr_t *_bitstr, int _nbits, int _size, int *_result)
-{
-	bit_ffs_area_at(_bitstr, /*start*/0, _nbits, _size, _result);
-}
+#define bit_ffs_area(_bitstr, _nbits, _size, _resultp)			\
+	*(_resultp) = bit_ff_area_at_((_bitstr), 0, (_nbits), (_size), 1)
 
 /* Find contiguous sequence of at least size cleared bits in bit string */
-static inline void
-bit_ffc_area(bitstr_t *_bitstr, int _nbits, int _size, int *_result)
-{
-	bit_ffc_area_at(_bitstr, /*start*/0, _nbits, _size, _result);
-}
+#define bit_ffc_area(_bitstr, _nbits, _size, _resultp)			\
+	*(_resultp) = bit_ff_area_at_((_bitstr), 0, (_nbits), (_size), 0)
 
 /* Count the number of bits set in a bitstr of size _nbits at or after _start */
-static inline void
-bit_count(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
+static inline ssize_t
+bit_count_(bitstr_t *_bitstr, size_t _start, size_t _nbits)
 {
 	bitstr_t *_curbitstr, mask;
-	int _value = 0, curbitstr_len;
+	size_t curbitstr_len;
+	ssize_t _value = 0;
 
 	if (_start >= _nbits)
-		goto out;
+		return (0);
 
 	_curbitstr = _bitstr + _bit_idx(_start);
 	_nbits -= _BITSTR_BITS * _bit_idx(_start);
@@ -383,6 +356,8 @@ bit_count(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
 		mask = _bit_make_mask(_start, _bit_offset(curbitstr_len - 1));
 		_value += __bitcountl(*_curbitstr & mask);
 		_curbitstr++;
+		if (_nbits < _BITSTR_BITS)
+			return (_value);
 		_nbits -= _BITSTR_BITS;
 	}
 	while (_nbits >= (int)_BITSTR_BITS) {
@@ -395,23 +370,24 @@ bit_count(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
 		_value += __bitcountl(*_curbitstr & mask);
 	}
 
-out:
-	*_result = _value;
+	return (_value);
 }
+#define bit_count(_bitstr, _start, _nbits, _resultp)			\
+	*(_resultp) = bit_count_((_bitstr), (_start), (_nbits))
 
 /* Traverse all set bits, assigning each location in turn to iter */
 #define	bit_foreach_at(_bitstr, _start, _nbits, _iter)			\
-	for (bit_ffs_at((_bitstr), (_start), (_nbits), &(_iter));	\
+	for ((_iter) = bit_ff_at_((_bitstr), (_start), (_nbits), 1);	\
 	     (_iter) != -1;						\
-	     bit_ffs_at((_bitstr), (_iter) + 1, (_nbits), &(_iter)))
+	     (_iter) = bit_ff_at_((_bitstr), (_iter) + 1, (_nbits), 1))
 #define	bit_foreach(_bitstr, _nbits, _iter)				\
 	bit_foreach_at(_bitstr, /*start*/0, _nbits, _iter)
 
 /* Traverse all unset bits, assigning each location in turn to iter */
 #define	bit_foreach_unset_at(_bitstr, _start, _nbits, _iter)		\
-	for (bit_ffc_at((_bitstr), (_start), (_nbits), &(_iter));	\
+	for ((_iter) = bit_ff_at_((_bitstr), (_start), (_nbits), 0);	\
 	     (_iter) != -1;						\
-	     bit_ffc_at((_bitstr), (_iter) + 1, (_nbits), &(_iter)))
+	     (_iter) = bit_ff_at_((_bitstr), (_iter) + 1, (_nbits), 0))
 #define	bit_foreach_unset(_bitstr, _nbits, _iter)			\
 	bit_foreach_unset_at(_bitstr, /*start*/0, _nbits, _iter)
 
diff --git a/tests/sys/sys/bitstring_test.c b/tests/sys/sys/bitstring_test.c
index 0c214b9e67a7..a48042a4a063 100644
--- a/tests/sys/sys/bitstring_test.c
+++ b/tests/sys/sys/bitstring_test.c
@@ -1,5 +1,6 @@
 /*-
  * Copyright (c) 2014 Spectra Logic Corporation
+ * Copyright (c) 2023 Klara, Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,7 +32,7 @@
 #include <sys/param.h>
 
 #include <bitstring.h>
-#include <stdio.h>
+#include <malloc_np.h>
 
 #include <atf-c.h>
 
@@ -51,6 +52,7 @@ bitstring_run_heap_test(testfunc_t *test, int nbits)
 	bitstr_t *bitstr = bit_alloc(nbits);
 
 	test(bitstr, nbits, "heap");
+	free(bitstr);
 }
 
 static void
@@ -862,6 +864,91 @@ BITSTRING_TC_DEFINE(bit_foreach_unset_at)
 	}
 }
 
+/*
+ * Perform various tests on large bit strings.  We can't simply add larger
+ * sizes to bitstring_runner as most of the existing tests are exhaustive
+ * and would take forever to run for large values of nbits.
+ *
+ * On 32-bit platforms, we use nbits = SSIZE_MAX (2147483647) bits, which
+ * is the largest we can hope to support; on 64-bit platforms, we use
+ * nbits = INT_MAX + 30 (2147483677), which is small enough to be
+ * practicable yet large enough to reveal arithmetic overflow bugs.
+ */
+ATF_TC_WITHOUT_HEAD(bitstr_large);
+ATF_TC_BODY(bitstr_large, tc)
+{
+	size_t nbits  = INT_MAX < SSIZE_MAX ? (size_t)INT_MAX + 30 : SSIZE_MAX;
+	size_t early = 5, late = nbits - 5;
+	ssize_t fc, fs;
+	bitstr_t *b;
+
+	/* Check for overflow in size calculation */
+	ATF_REQUIRE(nbits >= (size_t)INT_MAX);
+	ATF_REQUIRE(bitstr_size(nbits) >= nbits / 8);
+
+	/* Allocate the bit string */
+	ATF_REQUIRE(b = bit_alloc(nbits));
+
+	/* Check that we allocated enough */
+	ATF_REQUIRE(malloc_usable_size(b) >= bitstr_size(nbits));
+
+	/* Check ffc, ffs on all-zeroes string */
+	bit_ffc(b, nbits, &fc);
+	ATF_CHECK_EQ(0L, fc);
+	bit_ffs(b, nbits, &fs);
+	ATF_CHECK_EQ(-1L, fs);
+
+	/* Set, test, and clear an early bit */
+	bit_set(b, early);
+	bit_ffs(b, nbits, &fs);
+	ATF_CHECK_EQ((ssize_t)early, fs);
+	ATF_CHECK_EQ(0, bit_test(b, early - 1));
+	ATF_CHECK(bit_test(b, early) != 0);
+	ATF_CHECK_EQ(0, bit_test(b, early + 1));
+	bit_clear(b, early);
+	ATF_CHECK_EQ(0, bit_test(b, early));
+
+	/* Set, test, and clear an early bit range */
+	bit_nset(b, early - 1, early + 1);
+	bit_ffs(b, nbits, &fs);
+	ATF_CHECK_EQ((ssize_t)early - 1, fs);
+	ATF_CHECK_EQ(0, bit_test(b, early - 2));
+	ATF_CHECK(bit_test(b, early - 1));
+	ATF_CHECK(bit_test(b, early));
+	ATF_CHECK(bit_test(b, early + 1));
+	ATF_CHECK_EQ(0, bit_test(b, early + 2));
+	bit_nclear(b, early - 1, early + 1);
+	ATF_CHECK_EQ(0, bit_test(b, early - 1));
+	ATF_CHECK_EQ(0, bit_test(b, early));
+	ATF_CHECK_EQ(0, bit_test(b, early + 1));
+
+	/* Set, test, and clear a late bit */
+	bit_set(b, late);
+	bit_ffs(b, nbits, &fs);
+	ATF_CHECK_EQ((ssize_t)late, fs);
+	ATF_CHECK_EQ(0, bit_test(b, late - 1));
+	ATF_CHECK(bit_test(b, late) != 0);
+	ATF_CHECK_EQ(0, bit_test(b, late + 1));
+	bit_clear(b, late);
+	ATF_CHECK_EQ(0, bit_test(b, late));
+
+	/* Set, test, and clear a late bit range */
+	bit_nset(b, late - 1, late + 1);
+	bit_ffs(b, nbits, &fs);
+	ATF_CHECK_EQ((ssize_t)late - 1, fs);
+	ATF_CHECK_EQ(0, bit_test(b, late - 2));
+	ATF_CHECK(bit_test(b, late - 1));
+	ATF_CHECK(bit_test(b, late));
+	ATF_CHECK(bit_test(b, late + 1));
+	ATF_CHECK_EQ(0, bit_test(b, late + 2));
+	bit_nclear(b, late - 1, late + 1);
+	ATF_CHECK_EQ(0, bit_test(b, late - 1));
+	ATF_CHECK_EQ(0, bit_test(b, late));
+	ATF_CHECK_EQ(0, bit_test(b, late + 1));
+
+	free(b);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
@@ -884,6 +971,7 @@ ATF_TP_ADD_TCS(tp)
 	BITSTRING_TC_ADD(tp, bit_foreach_at);
 	BITSTRING_TC_ADD(tp, bit_foreach_unset);
 	BITSTRING_TC_ADD(tp, bit_foreach_unset_at);
+	ATF_TP_ADD_TC(tp, bitstr_large);
 
 	return (atf_no_error());
 }