[PING 2][PATCH] issue -Wstring-compare in more case (PR 95673)

[Martin Sebor]

Ping: https://gcc.gnu.org/pipermail/gcc-patches/2020-October/555225.html

On 10/8/20 8:43 AM, Martin Sebor wrote:
> Ping: https://gcc.gnu.org/pipermail/gcc-patches/2020-October/555225.html
> 
> On 9/30/20 6:14 PM, Martin Sebor wrote:
>> -Wstring-compare triggers under the same strict conditions as
>> the strcmp/strncmp call is folded into a constant: only when
>> all the uses of the result are [in]equality expressions with
>> zero.  However, even when the call cannot be folded into
>> a constant because the result is in addition used in other
>> expressions besides equality to zero, GCC still sets the range
>> of the result to nonzero.  So in more complex functions where
>> some of the uses of the same result are in tests for equality
>> to zero and others in other expressions, the warning fails to
>> point out the very mistake it's designed to detect.
>>
>> The attached change enhances the function that determines how
>> the strcmp/strncmp is used to also make it possible to detect
>> the mistakes in the multi-use situations.
>>
>> Tested on x86_64-linux & by building Glibc and Binutils/GDB
>> and confirming it triggers no new warnings.
>>
>> Martin
>