Re: [1/2] PR 78736: New warning -Wenum-conversion

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

On 1 August 2017 at 00:10, Prathamesh Kulkarni
<prathamesh.kulkarni@linaro.org> wrote:
> On 11 July 2017 at 17:59, Prathamesh Kulkarni
> <prathamesh.kulkarni@linaro.org> wrote:
>> On 13 June 2017 at 01:47, Joseph Myers <joseph@codesourcery.com> wrote:
>>> This is OK with one fix:
>>>
>>>> +C ObjC Var(warn_enum_conversion) Init(0) Warning LangEnabledBy(C Objc,Wall)
>>>
>>> I believe the LangEnabledBy arguments are case-sensitive, so you need to
>>> have ObjC not Objc there for it to work correctly.  (*.opt parsing isn't
>>> very good at detecting typos and giving errors rather than silently
>>> ignoring things.)
>> Hi,
>> Sorry for the late response, I was on a vacation.
>> The attached patch is rebased and bootstrap+tested on x86_64-unknown-linux-gnu.
>> I have modified it slightly to not warn for enums with different names
>> but having same value ranges.
>> For eg:
>> enum e1 { e1_1, e1_2 };
>> enum e2 { e2_1, e2_2 };
>>
>> enum e1 x = e2_1;
>> With this version, there would be no warning for the above assignment
>> since both e1 and e2 have
>> same value ranges.  Is that OK ?
>>
>> The patch has following fallouts in the testsuite:
>>
>> a) libgomp:
>> I initially assume it was a false positive because I thought enum
>> gomp_schedule_type
>> and enum omp_sched_t have same value-ranges but it looks like omp_sched_t
>> has range [1, 4] while gomp_schedule_type has range [0, 4] with one
>> extra element.
>> Is the warning then correct for this case ?
>>
>> b) libgfortran:
>> i) Implicit conversion from unit_mode to file_mode
>> ii) Implicit conversion from unit_sign_s to unit_sign.
>> I suppose the warning is OK for these cases since unit_mode, file_mode
>> have different value-ranges and similarly for unit_sign_s, unit_sign ?
>>
>> Also I tested the warning by compiling the kernel for x86_64 with
>> allmodconifg (attached), and there
>> have been quite few instances of the warning (attached). I have been
>> through few cases which I don't think are false positives
>> but I wonder then whether we should relegate the warning to Wextra instead ?
> ping: https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00514.html
ping * 2 https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00514.html

Thanks,
Prathamesh
>
> Thanks,
> Prathamesh
>>
>> Thanks,
>> Prathamesh
>>>
>>> --
>>> Joseph S. Myers
>>> joseph@codesourcery.com