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Re: [PATCH] Add a character size parameter to c_strlen/get_range_strlen


On 08/21/2018 11:49 AM, Martin Sebor wrote:
> On 08/21/2018 09:44 AM, Joseph Myers wrote:
>> On Tue, 21 Aug 2018, Martin Sebor wrote:
>>
>>> Sure, but the only valid argument to %ls is wchar_t*.  Passing
>>> it something else is undefined.
>>
>> Well, (wchar_t *)"something\0\0\0\0" would be OK given
>> -fno-strict-aliasing and if you know the alignment is OK.  Do we have
>> that
>> information about the type cast to, as opposed to the type of the string
>> constant, at this point?
> 
> In the simple cases like the one above the cast is gone.  Only
> in some more involved cases is the type of the argument preserved.
> I responded to Jeff with one such example here:
> 
>   https://gcc.gnu.org/ml/gcc-patches/2018-08/msg01296.html
> 
> If supporting (wchar_t *)"...\0\0\0\0" with %ls is viewed as
> important (despite it being undefined) then the function does
> need an ELTSIZE argument so it knows what to count.  In that
> event, in order to detect the problem cases we have been
> discussing (missing nuls and mismatched argument types),
> the function it must not fail when ELTSIZE is not equal
> to the size of actual array element.  Instead, it needs to
> return the element type to the caller which then needs to
> do the validation and issue a diagnostic.
So I think that argues that the sanity check should be removed or
otherwise neutered when if/when we attack the argument type mismatching
problems.

Jeff


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