2

I have this struct definitions:

struct inner
{
    int i;
    std::string str;
};

struct outer
{
    inner member[32];
};

Now I want to create a value-initialized instance of outer, so I write

outer o = {};

With GCC, this works just fine: all inner.i are zeroed and all inner.str are empty. But on VS2013, only the inner.str are empty; all inner.i contain garbage i.e. are not properly initialized.

Without the std::string member, the zero-initialization of inner.i works with VS2013.

What does the standard say on this? I always assumed {} initializes everything, either by zeroing or by calling the default constructor. Am I wrong or is this a very bad bug in VS2013?

Horstling
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1 Answers1

2

This is simply aggregate initialization:

If the number of initializer clauses is less than the number of members or initializer list is completely empty, the remaining members are initialized by their default initializers, if provided in the class definition, and otherwise (since C++14) by empty lists, which performs value-initialization.

Value initialization means that every element of member is value-initialized, which in turn means that i should be zero.

So yes, this is a VS2013 bug.

orlp
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  • Would be a quite serious bug, right? Initializing stuff is not an exotic use case. – Horstling Nov 20 '15 at 11:07
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    That compiler often has quite serious bugs in the new features they claim are supported. They still don't have decent variadic templates even though they claimed support for it for three major versions in a row. – R. Martinho Fernandes Nov 20 '15 at 11:19