Re: [Qemu-devel] [PATCH v4 1/2] tests: Use real size for iov tests

[Juan Quintela <quintela@redhat.com>]

"Daniel P. Berrange" <berrange@redhat.com> wrote:
> On Fri, Sep 01, 2017 at 01:54:59PM +0200, Juan Quintela wrote:
>> We were using -1 instead of the real size because the functions check
>> what is bigger, size in bytes or the size of the iov.  Recent gcc's
>> barf at this.
>> 
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> Reviewed-by: Peter Xu <peterx@redhat.com>
>> Tested-by: Cleber Rosa <crosa@redhat.com>
>> --
>> 
>> Remove comments about this feature.
>> Fix missing -1.
>> ---
>>  include/qemu/iov.h |  6 ------
>>  tests/test-iov.c   | 10 +++++-----
>>  2 files changed, 5 insertions(+), 11 deletions(-)
>> 
>> diff --git a/include/qemu/iov.h b/include/qemu/iov.h
>> index bd9fd55b0a..72d4c559b4 100644
>> --- a/include/qemu/iov.h
>> +++ b/include/qemu/iov.h
>> @@ -31,11 +31,6 @@ size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
>>   * Number of bytes actually copied will be returned, which is
>>   *  min(bytes, iov_size(iov)-offset)
>>   * `Offset' must point to the inside of iovec.
>> - * It is okay to use very large value for `bytes' since we're
>> - * limited by the size of the iovec anyway, provided that the
>> - * buffer pointed to by buf has enough space.  One possible
>> - * such "large" value is -1 (sinice size_t is unsigned),
>> - * so specifying `-1' as `bytes' means 'up to the end of iovec'.
>>   */
>>  size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
>>                           size_t offset, const void *buf, size_t bytes);
>> @@ -76,7 +71,6 @@ iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
>>   * up to the end of it, will be filled with the specified value.
>>   * Function return actual number of bytes processed, which is
>>   * min(size, iov_size(iov) - offset).
>> - * Again, it is okay to use large value for `bytes' to mean "up to the end".
>>   */
>>  size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
>>                    size_t offset, int fillc, size_t bytes);
>
> I'm not sure its right to be removing these comments, unless you've
> audited the code to ensure no caller outside the test suite is
> relying on this documented behaviour.

I did.  The caller call with the real size of the buffer.
iov_memset() still works with the -1 size.

iov_to/from_buf, the non full versions don't work, because the inline
gets confused with -1 with newer gcc's.
>
> For the test-iov.c changes though you can have
>
> Reviewed-by: Daniel P. Berrange <berrange@redhat.com>

Later, Juan.