Get size of mem to free by free

[H.Loom via Digitalmars-d-learn]

On Friday, 5 August 2016 at 19:55:22 UTC, Mark "J" Twain wrote:
> I use malloc to allocate some memory, then free it later. For 
> monitoring purposes, I would like to know how much is free'ed 
> by free by just knowing the object. Or, rather, given a ptr 
> allocated by malloc, bet the block size it allocated from the 
> ptr alone.
>
> Some C compilers have special intrinsics and such for this, 
> does D have any ability? If not, any hacks? I just need 
> something that works.

You can wrap the C memory allocations functions with a version 
identifier, e.g


version(stat)
{
     __gshared size_t[size_t] sizes;
}

version(stat)
{
     auto malloc(size_t size)
     {
         auto result = std.c.stdlib.malloc;
         sizes[result] = size;
         return result;
     }
}
else alias malloc = std.c.stdlib.malloc;

version(stat)
{
     void free(void* ptr)
     {
         std.c.stdlib.free(ptr);
         sizes.remove(ptr);
     }
}
else alias free = std.c.stdlib.free;


that a bit a DIY but this would work.