[PATCH 2/3] bitmap: exclude nbits == 0 cases from bitmap test

Yury Norov
2026-03-19T00:44:00Z

Bitmap API handles nbits == 0 in most cases correctly, i.e. it doesn't
dereferene underlying bitmap and returns a sane value where convenient,
or implementation defined, or undef.

Implicitly testing nbits == 0 case, however, may make an impression that
this is a regular case. This is wrong. In most cases nbits == 0 is a
sign of an error on a client side. The tests should not make such an
implression.

This patch reworks the existing tests to not test nbits == 0. The
following patch adds an explicit test for it with an appropriate
precaution.

Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
lib/test_bitmap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index eeb497016ed3..b6f27c632c75 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -653,7 +653,7 @@ static void __init test_bitmap_arr32(void)

memset(arr, 0xa5, sizeof(arr));

- for (nbits = 0; nbits < EXP1_IN_BITS; ++nbits) {
+ for (nbits = 1; nbits < EXP1_IN_BITS; ++nbits) {
bitmap_to_arr32(arr, exp1, nbits);
bitmap_from_arr32(bmap2, arr, nbits);
expect_eq_bitmap(bmap2, exp1, nbits);
@@ -681,7 +681,7 @@ static void __init test_bitmap_arr64(void)

memset(arr, 0xa5, sizeof(arr));

- for (nbits = 0; nbits < EXP1_IN_BITS; ++nbits) {
+ for (nbits = 1; nbits < EXP1_IN_BITS; ++nbits) {
memset(bmap2, 0xff, sizeof(arr));
bitmap_to_arr64(arr, exp1, nbits);
bitmap_from_arr64(bmap2, arr, nbits);
@@ -714,7 +714,7 @@ static void noinline __init test_mem_optimisations(void)
unsigned int start, nbits;

for (start = 0; start < 1024; start += 8) {
- for (nbits = 0; nbits < 1024 - start; nbits += 8) {
+ for (nbits = 1; nbits < 1024 - start; nbits += 8) {
memset(bmap1, 0x5a, sizeof(bmap1));
memset(bmap2, 0x5a, sizeof(bmap2));

@@ -873,7 +873,7 @@ static void __init test_bitmap_weight(void)

/* Test outline implementation */
w = bitmap_weight(exp1, EXP1_IN_BITS);
- for (bit = 0; bit < EXP1_IN_BITS; bit++) {
+ for (bit = 1; bit < EXP1_IN_BITS; bit++) {
w1 = bitmap_weight(exp1, bit);
w2 = bitmap_weight_from(exp1, bit, EXP1_IN_BITS);
expect_eq_uint(w1 + w2, w);
--
2.43.0