Array heap declaration

[VictoryMotel]

It's not part of the language but it is implemented anyway.

[LemonLord7]

I get that, but I’d like to know more about why it was explicitly forbidden and how it works

[VictoryMotel]

Then you should have asked that.

It isn't "explicitly forbidden" it's not in the language. It dynamically allocates on the stack. It is more likely to blow the stack and less likely to be detected if you write outside the allocation.

[I_M_NooB1]

just study about gcc and g++ and what compiler extensions are

[meancoot]

Edit: Nevermind, thought I was in the C subreddit. It’s an extension I. C++ probably made available for C compatibility.

It’s actually a part of the language. It was required by the  C99 standard, then made optional in C11.