Function realloc 

pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8

Reallocates memory with the global allocator.

This function forwards calls to the GlobalAlloc::realloc method of the allocator registered with the #[global_allocator] attribute if there is one, or the std crate’s default.

This function is expected to be deprecated in favor of the grow and shrink methods of the [Global] type when it and the [Allocator] trait become stable.

Safety

See GlobalAlloc::realloc.