[lttng-dev] [PATCH babeltrace 1/1] Fix: test_bitfield: extend coverage: 0-len signed write/read

[Mathieu Desnoyers]

By convention, a 0-len bitfield write is a no-op, and a 0-len read
sets the value of the output to 0.

So we can "encode" the value 0 over a length of 0 bit. Cover this
in the test-cases for signed types. It is already covered for the
unsigned test-cases.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Change-Id: Ib6038b98167ef2cfa8c504d7ac29498e71827b38
---
 tests/lib/test_bitfield.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/tests/lib/test_bitfield.c b/tests/lib/test_bitfield.c
index 5188335b..05547c07 100644
--- a/tests/lib/test_bitfield.c
+++ b/tests/lib/test_bitfield.c
@@ -391,7 +391,9 @@ void run_test_signed_write(int src_i, long long src_ll)
 	long long readval;
 	unsigned int s, l;
 
-	if (src_i & 0x80000000U)
+	if (!src_i)
+		nrbits_i = 0;			/* The number of bits needed to represent 0 is 0. */
+	else if (src_i & 0x80000000U)
 		nrbits_i = fls_u32(~src_i) + 1;	/* Find least significant bit conveying sign */
 	else
 		nrbits_i = fls_u32(src_i) + 1;	/* Keep sign at 0 */
@@ -442,7 +444,9 @@ void run_test_signed_write(int src_i, long long src_ll)
 	}
 	pass(SIGNED_INT_WRITE_TEST_DESC_FMT_STR, src_i);
 
-	if (src_ll & 0x8000000000000000ULL)
+	if (!src_ll)
+		nrbits_ll = 0;				/* The number of bits needed to represent 0 is 0. */
+	else if (src_ll & 0x8000000000000000ULL)
 		nrbits_ll = fls_u64(~src_ll) + 1;	/* Find least significant bit conveying sign */
 	else
 		nrbits_ll = fls_u64(src_ll) + 1;	/* Keep sign at 0 */
@@ -507,7 +511,9 @@ void run_test_signed_read(int src_i, long long src_ll)
 	long long readval_ll;
 	unsigned int s, l;
 
-	if (src_i & 0x80000000U)
+	if (!src_i)
+		nrbits_i = 0;			/* The number of bits needed to represent 0 is 0. */
+	else if (src_i & 0x80000000U)
 		nrbits_i = fls_u32(~src_i) + 1;	/* Find least significant bit conveying sign */
 	else
 		nrbits_i = fls_u32(src_i) + 1;	/* Keep sign at 0 */
@@ -558,6 +564,8 @@ void run_test_signed_read(int src_i, long long src_ll)
 	}
 	pass(SIGNED_INT_READ_TEST_DESC_FMT_STR, src_i);
 
+	if (!src_ll)
+		nrbits_ll = 0;				/* The number of bits needed to represent 0 is 0. */
 	if (src_ll & 0x8000000000000000ULL)
 		nrbits_ll = fls_u64(~src_ll) + 1;	/* Find least significant bit conveying sign */
 	else
-- 
2.11.0