I'm getting the following warning on building libc++:
../src/locale.cpp:4554:14: warning: missing field 'tm_min' initializer [-Wmissing-field-initializers]
tm t = {0};
^
1 warning generated.
I know what the warning is saying. My question is why? I presume tm_min is getting initialized to 0 as intended. The above is pretty standard fare (I thought) for zero-initializing an aggregate. Isn't this warning a little too chatty?
Howard
It seems to me a little hard to separate this case from the general
case the warning is trying to implement - except that, yes, this seems
like a fairly common idiom even if it's no more useful than {}.
But someone had the same question about GCC with a more in-depth
rationalization (apparently {0} has special behavior in C99 that
differs from {}) & so they changed their behavior do fulfill your
request ( 36750 – -Wmissing-field-initializers relaxation request ). We
should probably do the same, I suppose.
- David
-Wmissing-field-initializers does have a special case for intentional uses of the language's default-zero-initialization rules. However, that special case is spelled {}, not {0}. If you feel that this is a really common idiom for zero-initialization, we could also add it, but I'd really prefer not to, because it neuters -Wmissing-field-initializers on an interesting class of bugs.
I acknowledge the argument for {0} being a more explicit "I want to zero-initialize this whole thing", but I don't actually agree. Neither {} nor {0} is being used for its obvious, literal meaning ("there is nothing to initialize here" and "there is one thing to initialize here, and I want it to be zero", respectively). Both expect the code-reader to understand the language's implicit-initialization rules. The first, however, is pretty obviously not the programmer's intended meaning when used to initialize an object that's known to carry information.
John.
I'm content with:
#pragma clang diagnostic ignored "-Wmissing-field-initializers"
for libc++ code. Though I do suspect that this issue will come again with someone else.
Howard
But using {}, as you suggest, gives:
warning: use of GNU empty initializer extension [-pedantic,-Wgnu]
One seems trapped between one warning or the other.
Only in C; C++ allows {}.
-Eli
-Wmissing-field-initializers does have a special case for intentional
uses of the language's default-zero-initialization rules. However, that
special case is spelled {}, not {0}. If you feel that this is a really
common idiom for zero-initialization, we could also add it, but I'd
really prefer not to, because it neuters -Wmissing-field-initializers on
an interesting class of bugs.But using {}, as you suggest, gives:
warning: use of GNU empty initializer extension [-pedantic,-Wgnu]
This is one of my consistent blind spots; it surprises me every single time.
Although we were talking about C++ here, where {} is permitted.
One seems trapped between one warning or the other.
I agree that something should probably be done for the C case.
If that means white-listing {0}, okay. I'd still prefer to only do so in C,
since the better option is available in C++.
John.