Pay as you go is really going to make a difference

[norm]

On Saturday, 25 January 2020 at 16:07:24 UTC, Steven 
Schveighoffer wrote:
> On 1/24/20 5:20 PM, Gregor Mückl wrote:
>
>> So there's a couple of calls that should be fairly fast 
>> (clock_getres etc.). Why does the runtime need to read 
>> /proc/self/maps, though?
>
> This is great stuff, thanks!
>
> Note that /proc/self/maps appears nowhere in phobos or 
> druntime. So I'm assuming that's some other function that's 
> doing it (maybe in libc?)
>
> The clock_getres calls are so you can use core.time.MonoTime. 
> rt_init initializes those so they can be used early in the 
> process. I would assume those are really fast, as they are 
> constants in the kernel.
>
> -Steve

I was curious so I ran a quick strace hello world experiment 
using only printf, not writeln, compiled with D (DMD), C++ and C 
(gcc and clang). Only the D binary opens /proc/self/maps. Running 
`strace dmd --version` also opens /proc/self/maps, but I guess 
that makes sense since the compiler itself is now written in D.

===
// D hello world
import core.stdc.stdio;

int main() {
   printf("Hello world\n");
   return 0;
}

// CC and C hello world
#include <stdio.h>

int main() {
   printf("Hello world\n");
   return 0;
}
===


Cheers,
Norm