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SubjectRe: [PATCH v3 2/2] lib/test-string_helpers.c: add string_get_size() tests
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Andy Shevchenko <andriy.shevchenko@linux.intel.com> writes:

> On Tue, 2015-09-15 at 00:00 +0200, Rasmus Villemoes wrote:
>> On Mon, Sep 14 2015, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>>
>
> Vitaly, thanks for the test cases. My comments below.
>
>> > +static __init void test_string_get_size_one(u64 size, u64
>> > blk_size,
>> > + const enum
>> > string_size_units units,
>> > + const char
>> > *exp_result)
>> > +{
>> > + char buf[256];
>> > +
>> > + string_get_size(size, blk_size, units, buf, sizeof(buf));
>> > + if (!strncmp(buf, exp_result, min(sizeof(buf),
>> > strlen(exp_result))))
>> > + return;
>>
>> Nits: It probably makes sense to also test that string_get_size
>> '\0'-terminates the buffer, so I'd spell this
>>
>> if (!memcmp(buf, exp_result, min(sizeof(buf),
>> strlen(exp_result)+1)))
>>
>> With a generous stack buffer, that min() will always evaluate to the
>> strlen(exp_result)+1. On that note: Maybe 256 is a bit excessive. I
>> don't think this will run very deep in the kernel stack, but the code
>> might
>> get copy-pasted somewhere else. 16 should be plenty.
>
> Agree with Rasmus.
>
> And just to make a side note that useless use of min() since we have
> strnlen() :-)
>
>>
>> > + pr_warn("Test 'test_string_get_size_one' failed!\n");
>> > + pr_warn("string_get_size(size = %llu, blk_size = %llu,
>> > units = %d\n",
>> > + size, blk_size, units);
>>
>> [There's probably no pretty way of getting from units to a text
>> representation, but it's slightly annoying to have to check the
>> source
>> for the enum definition to figure out what units=0 or units=1 means.]
>>
>> > + pr_warn("expected: %s, got %s\n", exp_result, buf);
>>
>> In case we failed to '\0'-terminate buf, we might want to print it
>> with
>> "%.*s", (int)sizeof(buf), buf. But maybe I'm just overly paranoid.
>
> I prefer to put '\0' at the position after we expected have an actual
> '\0'. In this case we always be NULL terminated. I did this for hexdump
> test cases.

Just to check I got your suggestions right:

...
+ if (!memcmp(buf, exp_result, strnlen(exp_result, sizeof(buf) - 1) + 1))
+ return;
+
+ /* NULL terminate buf right after the expected '\0' */
+ buf[strnlen(exp_result, sizeof(buf) - 2) + 1] = '\0';
...

Alternatively, we could have avoided strnlen() by asserting
strlen(exp_result) < sizeof(buf) - 1 at the very beginning.

--
Vitaly


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