也许我不是来自这个星球，但在我看来，以下应该是一个语法错误:

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

但事实并非如此。当这段代码在Visual Studio上编译时，我很惊讶，但我已经学会了不相信MSVC编译器，就c++规则而言，所以我检查了标准，它也是标准允许的。如果你不相信的话，语法规则可以参考8.5.1。

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.

那么，有什么特别的原因，这个多余的逗号是明确允许的吗?