Why is clang++ warning "suggest braces around initialization of subobject [-Wmissing-braces]"?

Question

I have this code:

#include <array>

int main(int, char **argv)
{
   std::array<int, 3> a = {1,2,3};
}

This compiles fine (-std=c++11) , but if you include -Wall it gives this warning that I don't understand:

clang_pp_error.cpp:5:28: warning: suggest braces around initialization of subobject [-Wmissing-braces]
   std::array<int, 3> a = {1,2,3};
                           ^~~~~
                           {    }

score 27 · Accepted Answer · edited May 23 '17 at 12:10

27

This should be a bug: https://llvm.org/bugs/show_bug.cgi?id=21629.

See also Is it wise to ignore gcc/clang's "-Wmissing-braces" warning?.

edited May 23 '17 at 12:10

Community

1
1

answered Oct 23 '15 at 15:21

FrankHB

2,297
23
19

7

This warning should not be suppressed. If the code is according to C++11, initializer list using `{{ .. }}` is recommended instead of single `{ .. }`. There is a purpose for it and hence the warning should not be suppressed instead of improving the code that can cause problems later. – Sohail Si May 17 '17 at 17:12
3

@SohailSi This can be useful to prevent confusion between subobject to be initialized and the object being initialized, but it's plain wrong for cases like `std::array`, where the enclosing class is intended to be the replacement of the only array data member. Enforcement of this warning on such cases leaks the implementation details. Before it can be suppressed separately by somewhat portable means (e.g. attributes), it is not wise to be enabled by default. – FrankHB May 26 '17 at 04:24

score 24 · Answer 2 · edited May 23 '17 at 11:47

24

Use std::array<int, 3> a = {{1,2,3}}; instead.

See Why wasn't a double curly braces syntax preferred for constructors taking a std::initializer_list

edited May 23 '17 at 11:47

Community

1
1

answered Dec 23 '16 at 13:45

Sohail Si

2,750
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36

Why is clang++ warning "suggest braces around initialization of subobject [-Wmissing-braces]"?

2 Answers2