Stack or Heap

[Skarmander]

I would actually expect VLA's to implemented under the hood,
as a malloc call with a free at the end of the block,
and some kludge to accomodate the sizeof operator.

Unless the platform has the equivalent of alloca(), of course.

Even without it, it is very likely that for local allocations
specialized versions of malloc() will provide some benefit.

S.

 

[Keith Thompson]

I would actually expect VLA's to implemented under the hood,
as a malloc call with a free at the end of the block,
and some kludge to accomodate the sizeof operator.

I wouldn't, though it's certainly a possible implementation. I'd
expect VLAs to be implemented on most platforms by extending the
stack, in a manner very similar to allocating an ordinary (fixed-size)
stack frame or calling the non-standard function alloca().

 

[jacob navia]

pete a écrit :

I would actually expect VLA's to implemented under the hood,
as a malloc call with a free at the end of the block,
and some kludge to accomodate the sizeof operator.

lcc-win32 implements it by extending the stack. This is tricky
under windows since if you allocate more than 4096 bytes you
should implement a loop touching each page at least once to make the
stack grow...