[PATCH v2] mbstowcs: Document, test, and fix null pointer dst semantics (Bug 25219)

[Carlos O'Donell]

On 6/1/20 12:17 PM, Florian Weimer wrote:
> * Carlos O'Donell via Libc-alpha:
> 
>> +If @var{wstring} is a null pointer then no output is written and the
>> +conversion proceeds as above, and the result is returned. In practice
> 
> Missing two spaces after sentence-ending period.

Fixed.

>> +such behaviour is useful for calculating the exact number of wide
>> +characters required to convert @var{string}.  This behaviour of
>> +accepting a null pointer for @var{wstring} is an @w{XPG4.2} extension to
>> +the requirements in @w{ISO C} and @w{POSIX}.
> 
> Drop POSIX here?  Aren't the XSI-shaded bits of POSIX still POSIX?

You can still be POSIX compliant but not XSI-conforming implementation?

How about this?
~~~
This behaviour of accepting a null pointer for @var{wstring} is an @w{XPG4.2}
extension that is not specified in @w{ISO C} and is optional in @w{POSIX}.
~~~

>> diff --git a/wcsmbs/tst-mbstowcs.c b/wcsmbs/tst-mbstowcs.c
>> new file mode 100644
>> index 0000000000..903ad55102
>> --- /dev/null
>> +++ b/wcsmbs/tst-mbstowcs.c
> 
>> +  /* The input ASCII string in the C/POSIX locale must convert
>> +     to the matching WSTRING.  */
>> +  result = mbstowcs (wout, string, NUM_WCHAR);
>> +  TEST_VERIFY (result == (NUM_WCHAR - 1));
>> +  TEST_COMPARE_BLOB (wstring, sizeof(wchar_t) * (NUM_WCHAR - 1),
>> +		     wout, sizeof(wchar_t) * result);
> 
> Missing space after sizeof (twice).

Fixed.

-- 
Cheers,
Carlos.