[PATCH] D157879: [clang] Report missing designated initializers in C++

[Arthur Eubanks via Phabricator via cfe-commits]

aeubanks added a comment.

In D157879#4606531 <https://reviews.llvm.org/D157879#4606531>, @aaron.ballman wrote:

> In D157879#4604288 <https://reviews.llvm.org/D157879#4604288>, @phosek wrote:
>
>> Note that there's an ongoing discussion on the GCC bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96868 whether `-Wmissing-field-initializers` should apply to both C and C++ or just C.
>
> Thank you for posting this! I'm with @jwakely on this: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96868#c3 -- the warning is for people who want to be told they've not explicitly specified all of the initializers, it is not for telling you "this hasn't been initialized". I think the desire makes as much sense in C++ as it does in C, but this is more of a style warning than a correctness warning.
>
> In D157879#4604471 <https://reviews.llvm.org/D157879#4604471>, @ianloic wrote:
>
>> In D157879#4604233 <https://reviews.llvm.org/D157879#4604233>, @aeubanks wrote:
>>
>>> ah I thought this was in `-Wall` but it's not
>>>
>>> the struct is
>>>
>>>   struct Foo {
>>>     const void* buffer;
>>>     uint32_t capacity;
>>>     uint32_t reserved;
>>>   };
>>>
>>> where `reserved` isn't explicitly initialized. that seems like reasonable code, but I suppose we can just explicitly initialize `reserved` here
>>
>> FWIW, if this is the specific piece of code that led me to this conversation, that declaration is in a header which at least in theory is supposed to remain compatible with C. It's inside `extern "C" { ... }` even. We can't add explicit initialize `reserved` and keep the definition C comaptible.
>
> Ouch, yeah, that does make it a challenge. But why is `-Wmissing-field-initializers` enabled in the first place for the code? It seems like there are fields you *don't* want explicit initialization for, so perhaps the answer is to disable the diagnostic for those types?

It's an unfortunate configuration. We saw this in Chrome where some projects were manually setting `-Wmissing-field-initializers`, but when building for Fuchsia, some Fuchsia system headers had this code. We can just suppress this for all Fuchsia builds, I think that's fine.


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