int a[] = {1,2,}; Why is a trailing comma in an initializer-list allowed?

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Maybe I am not from this planet, but it would seem to me that the following should be a syntax error:

int a[] = {1,2,}; //extra comma in the end

But it’s not. I was surprised when this code compiled on Visual Studio, but I have learnt not to trust MSVC compiler as far as C++ rules are concerned, so I checked the standard and it is allowed by the standard as well. You can see 8.5.1 for the grammar rules if you don’t believe me.

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Why is this allowed? This may be a stupid useless question but I want you to understand why I am asking. If it were a sub-case of a general grammar rule, I would understand – they decided not to make the general grammar any more difficult just to disallow a redundant comma at the end of an initializer list. But no, the additional comma is explicitly allowed. For example, it isn’t allowed to have a redundant comma in the end of a function-call argument list (when the function takes ...), which is normal.

So, again, is there any particular reason this redundant comma is explicitly allowed?

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