PING [PATCH] restore ancient -Waddress for weak symbols [PR33925]

[Martin Sebor <msebor@gmail.com>]

Ping:
https://gcc.gnu.org/pipermail/gcc-patches/2021-October/582415.html

On 10/23/21 5:06 PM, Martin Sebor wrote:
> On 10/4/21 3:37 PM, Jason Merrill wrote:
>> On 10/4/21 14:42, Martin Sebor wrote:
>>> While resolving the recent -Waddress enhancement request (PR
>>> PR102103) I came across a 2007 problem report about GCC 4 having
>>> stopped warning for using the address of inline functions in
>>> equality comparisons with null.  With inline functions being
>>> commonplace in C++ this seems like an important use case for
>>> the warning.
>>>
>>> The change that resulted in suppressing the warning in these
>>> cases was introduced inadvertently in a fix for PR 22252.
>>>
>>> To restore the warning, the attached patch enhances
>>> the decl_with_nonnull_addr_p() function to return true also for
>>> weak symbols for which a definition has been provided.
>>
>> I think you probably want to merge this function with 
>> fold-const.c:maybe_nonzero_address, which already handles more cases.
> 
> maybe_nonzero_address() doesn't behave quite like
> decl_with_nonnull_addr_p() expects and I'm reluctant to muck
> around with the former too much since it's used for codegen,
> while the latter just for warnings.  (There is even a case
> where the functions don't behave the same, and would result
> in different warnings between C and C++ without some extra
> help.)
> 
> So in the attached revision I just have maybe_nonzero_address()
> call decl_with_nonnull_addr_p() and then refine the failing
> (or uncertain) cases separately, with some overlap between
> them.
> 
> Since I worked on this someone complained that some instances
> of the warning newly enhanced under PR102103 aren't suppresed
> in code resulting from macro expansion.  Since it's trivial,
> I include the fix for that report in this patch as well.
> 
> Tested on x86_64-linux.
> 
> Martin