alloca is slow and dangerous

[Ola Fosheim Grostad]

On Friday, 1 January 2021 at 17:55:33 UTC, Steven Schveighoffer 
wrote:
> In my experience, using it isn't extremely beneficial -- since 
> it's in stdc, it requires the c library, which means you have 
> malloc/free, which is much safer/usable.

I never use alloca directly, but in C you can just use an int 
variable for the dynamic array size. I find that useful for 
things like building a zero terminated path that only will be 
used with one function call. Or for a FFT buffer that is only 
known at runtime and I want to use hot memory (already in cache).

To do that fixed size would take maybe 200 KB, could easily be 
100 times more than needed... And the next stack frame would be 
cold as hell...