[PATCH,c++] use XALLOCAVEC in the C++ front-end

[Manuel López-Ibáñez]

On 9 June 2010 13:33, Gabriel Dos Reis <gdr@integrable-solutions.net> wrote:
> On Wed, Jun 9, 2010 at 4:53 AM, Manuel López-Ibáñez
> <lopezibanez@gmail.com> wrote:
>> On 8 June 2010 18:14, Jason Merrill <jason@redhat.com> wrote:
>>> On 06/08/2010 10:43 AM, Manuel López-Ibáñez wrote:
>>>>
>>>> On 8 June 2010 16:06, Jason Merrill<jason@redhat.com>  wrote:
>>>
>>>>> The error message is unclear, but the issue is that converting from
>>>>> char**
>>>>> to char const** is unsafe, while converting to char const*const* is safe.
>>>>
>>>> What does it mean unsafe in this context? I could produce a patch that
>>>> changes the message but I would like to be sure what to say.
>>>>
>>>> semantics.c:1223:7: error: new ‘const’ qualifier in cast from 'char
>>>> **' to 'const char **' is unsafe [-Werror=cast-qual]
>>> Explanation from the C++ standard (4.4 [conv.qual]):
>>>
>>> [ Note: if a program could assign a pointer of type T** to a pointer of type
>>> const T** (that is, if line #1 below were allowed), a program could
>>> inadvertently modify a const object (as it is done on line #2). For example,
>>>
>>>  int main() {
>>>    const char c = ’c’;
>>>    char* pc;
>>>    const char** pcc = &pc;// #1: not allowed
>>>    *pcc = &c;
>>>    *pc = ’C’; // #2: modifies a const object
>>>  }
>>> --end note ]
>>
>> So what do you think about the following message:
>>
>> error: new ‘const’ qualifier in cast from 'char **' to 'const char **'
>> is unsafe [-Werror=cast-qual]
>> note: to be safe all intermediate pointers must be equally qualified
>
> that is OK; but I find the leading 'new' hard to parse.   Please, just
> remove it.
>

Anyway, this is the C FE. The C++ FE gives the following:

test.C:4:23: warning: invalid conversion from ‘char**’ to ‘const
char**’ [-fpermissive]

but the code is too intricate to give a clearer error in the case of
C++ or to factor out the common check.

Cheers,

Manuel.