John Carmack applauds D's pure attribute

Walter Bright newshound2 at
Sat Feb 25 14:55:36 PST 2012

On 2/25/2012 2:08 PM, Paulo Pinto wrote:
> Most standard compiler malloc()/free() implementations are actually slower than
> most advanced GC algorithms.

Most straight up GC vs malloc/free benchmarks miss something crucial. A GC 
allows one to do substantially *fewer* allocations. It's a lot faster to not 
allocate than to allocate.

Consider C strings. You need to keep track of ownership of it. That often means 
creating extra copies, rather than sharing a single copy.

Enter C++'s shared_ptr. But that works by, for each object, allocating a 
*second* chunk of memory to hold the reference count. Right off the bat, you've 
got twice as many allocations & frees with shared_ptr than a GC would have.

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