On Thursday, 8 February 2018 at 11:23:43 UTC, Daniel Kozak wrote:
I mean scope(success), for scope(exit) there is no speed penalty
On Thu, Feb 8, 2018 at 12:03 PM, Daniel Kozak
<[email protected]> wrote:
Yes, it add, but is almost zero
On Thu, Feb 8, 2018 at 12:00 PM, Timothee Cour via
Digitalmars-d-learn < [email protected]> wrote:
I know that, my question is whether it adds any runtime
overhead over naive way (which is to call the "bar" finalizer
before each return statement) in the case where no exception
is thrown
On Thu, Feb 8, 2018 at 2:44 AM, Mike Parker via
Digitalmars-d-learn <[email protected]> wrote:
> On Thursday, 8 February 2018 at 10:09:12 UTC, Timothee Cour
> wrote:
>>
>> I'm curious whether scope guards add any cost over the
>> naive way, eg:
>>
>> ```
>> void fun(){
>> ...
>> scope(success) {bar;}
>> ...
>> }
>> ```
>>
>> vs:
>>
>> ```
>> void fun(){
>> ...
>> if(foo1){
>> bar; // add this before each return
>> return;
>> }
>> ...
>> bar;
>> return;
>> }
>> ```
>>
>> For scope(success) and scope(failure), the naive way would
>> anyway
>> involve try/catch statements but what about scope(exit)?
>> Does the
>> zero-cost exception model (zero cost being for non-thrown
>> exceptions)
>> guarantee us that scope(success) has 0 overhead over naive
>> way?
>
>
> Scope guards are lowered to the equivalent
> try/catch/finally blocks
anyway.
Yes, it's easy to see this when looking at the lowered AST and
ASM.
1) AST
https://run.dlang.io/is/KNJbnP
---
import object;
import core.stdc.stdio;
void main()
{
printf("%s", "All good.");
printf("%s", "FOO");
return 0;
}
---
2) ASM
https://run.dlang.io/is/bIVYvi
---
_Dmain:
push RBP
mov RBP,RSP
lea RSI,FLAT:.rodata[00h][RIP]
lea RDI,FLAT:.rodata[00h][RIP]
xor EAX,EAX
call printf@PLT32
lea RSI,FLAT:.rodata[00h][RIP]
lea RDI,FLAT:.rodata[00h][RIP]
xor EAX,EAX
call printf@PLT32
xor EAX,EAX
pop RBP
ret
---
