On 04/06/2017 12:55 PM, Eric Blake wrote:
On 04/06/2017 10:49 AM, Eric Blake wrote:
On 04/06/2017 10:41 AM, Dr. David Alan Gilbert (git) wrote:
From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
boolean; it's got a point.
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
tests/check-qdict.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tests/check-qdict.c b/tests/check-qdict.c
index 81162ee572..6f3fbcf9c1 100644
--- a/tests/check-qdict.c
+++ b/tests/check-qdict.c
@@ -559,7 +559,7 @@ static void qdict_join_test(void)
g_assert(qdict_size(dict1) == 2);
g_assert(qdict_size(dict2) == !overwrite);
- g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
+ g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
How is the test passing pre-patch, and why does it not change the test
post-patch? Does that mean that overwrite is not doing what we expected?
Replying to myself:
Pre-patch, it was reached twice (once for overwrite=false, once for
overwrite=true), as:
(42 == false) ? 84 : 42
(84 == true) ? 84 : 42
which simplifies to 42 on both iterations, and g_assert(42) succeeds.
In fact, this is a tautology - no matter WHAT value we encounter, the
assert succeeds, so we are not actually testing that the value matters.
Post-patch, it becomes:
42 == (false ? 84 : 42)
84 == (true ? 84 : 42)
which is then asserting that we actually have the value we expect.
Reviewed-by: Eric Blake <ebl...@redhat.com>
Safe for 2.9, but late enough that it also doesn't matter if it slips
until 2.10.
another case which demonstrate human _optimized_ C is more bug prone
than verbose basic code...
Most cpp generates the same asm code with the following C:
if (overwrite) {
g_assert(qdict_get_int(dict1, "foo") == 84);
} else {
g_assert(qdict_get_int(dict1, "foo") == 42);
}
Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
