Akihiko Odaki writes:
> A string that represents a double can be long if it is an exponentially
> large number.
I'd like us to spell out that this is cleanup, not a bug fix. I suggest
to start with the warning. Something like this:
tests: Clean up double comparisons to avoid compiler warning
To enable -Wformat-overflow=2, we need to clean up a couple of false
positives:
Now explain why they are false:
These buffers cannot actually overflow because the doubles are
between 0 and 31.0/3 inclusive.
Then justify the solution:
However, formatting doubles just to compare them is silly. Compare
them directly instead. To avoid potential rounding trouble, change
the numbers tested to be representable exactly in double.
> Signed-off-by: Akihiko Odaki
> ---
> tests/unit/test-qobject-input-visitor.c | 8 ++--
> tests/unit/test-qobject-output-visitor.c | 7 ++-
> 2 files changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/tests/unit/test-qobject-input-visitor.c
> b/tests/unit/test-qobject-input-visitor.c
> index 84bdcdf702e0..beee11db4e47 100644
> --- a/tests/unit/test-qobject-input-visitor.c
> +++ b/tests/unit/test-qobject-input-visitor.c
> @@ -500,7 +500,7 @@ static void
> test_visitor_in_list_struct(TestInputVisitorData *data,
> g_string_append_printf(json, "'number': [");
> sep = "";
> for (i = 0; i < 32; i++) {
> -g_string_append_printf(json, "%s%f", sep, (double)i / 3);
> +g_string_append_printf(json, "%s%f", sep, (double)i / FLT_RADIX);
> sep = ", ";
> }
> g_string_append_printf(json, "], ");
> @@ -583,11 +583,7 @@ static void
> test_visitor_in_list_struct(TestInputVisitorData *data,
>
> i = 0;
> for (num_list = arrs->number; num_list; num_list = num_list->next) {
> -char expected[32], actual[32];
> -
> -sprintf(expected, "%.6f", (double)i / 3);
> -sprintf(actual, "%.6f", num_list->value);
> -g_assert_cmpstr(expected, ==, actual);
> +g_assert_cmpfloat(num_list->value, ==, (double)i / FLT_RADIX);
> i++;
> }
>
> diff --git a/tests/unit/test-qobject-output-visitor.c
> b/tests/unit/test-qobject-output-visitor.c
> index 407ab9ed505a..3c47b28f6638 100644
> --- a/tests/unit/test-qobject-output-visitor.c
> +++ b/tests/unit/test-qobject-output-visitor.c
> @@ -538,7 +538,7 @@ static void
> test_visitor_out_list_struct(TestOutputVisitorData *data,
> }
>
> for (i = 31; i >= 0; i--) {
> -QAPI_LIST_PREPEND(arrs->number, (double)i / 3);
> +QAPI_LIST_PREPEND(arrs->number, (double)i / FLT_RADIX);
> }
>
> for (i = 31; i >= 0; i--) {
> @@ -571,12 +571,9 @@ static void
> test_visitor_out_list_struct(TestOutputVisitorData *data,
> i = 0;
> QLIST_FOREACH_ENTRY(qlist, e) {
> QNum *qvalue = qobject_to(QNum, qlist_entry_obj(e));
> -char expected[32], actual[32];
>
> g_assert(qvalue);
> -sprintf(expected, "%.6f", (double)i / 3);
> -sprintf(actual, "%.6f", qnum_get_double(qvalue));
> -g_assert_cmpstr(actual, ==, expected);
> +g_assert_cmpfloat(qnum_get_double(qvalue), ==, (double)i /
> FLT_RADIX);
> i++;
> }
With an improved commit message
Reviewed-by: Markus Armbruster
