Re: [PATCH] Implement a warning for bogus sizeof(pointer) / sizeof(pointer[0])

[Martin Sebor <msebor@gmail.com>]

On 04/28/2017 08:12 AM, Bernd Edlinger wrote:
> On 04/28/17 00:52, Martin Sebor wrote:
>>>> I suggest avoiding "element size" because the pointed-to argument
>>>> need not be an array.  Mentioning the types should help users better
>>>> understand the problem (especially in C++ where types are often
>>>> obscured by layers of templates).  It might also be a nice touch
>>>> to add a note pointing to the declaration of the first sizeof
>>>> operand (if it's an object).
>>>>
>>>
>>> Yes, many thanks for your suggestions.
>>>
>>> Do the new warning and info messages look right?
>>
>> Sorry for not replying sooner.  The new warning looks good to
>> me, with just one minor nit.  For proper highlighting within
>> the message, the expression should be quoted in a pair of %<
>> and %> directives, like so:
>>
>>   warning_at (stack[sp].loc, OPT_Wsizeof_pointer_div,
>>               "division %<sizeof (%T) / sizeof (%T)%> does "
>>               "not compute the number of array elements",
>>               type0, type1))
>>
>> This way the whole quoted expression will be highlighted in
>> the style appropriate for quoted text.
>>
>> Similarly, in the inform call, sizeof should be quoted in
>> the same pair of %< and %> directives.
>>
>
> Do you want me to change the %qT format strings to %T ?

Yes, with the surrounding %< and %> the nested directives should
use the unquoted forms, otherwise the printer would end up quoting
both the whole expression and the type operand.

FWIW, to help avoid this mistake, I think this might be something
for GCC -Wformat to warn on and the pretty-printer to detect (and
ICE on).

Martin