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

[Prathamesh Kulkarni <prathamesh dot kulkarni at linaro dot org>]

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 ?

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

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