Hello bearophile,
If there are guarantees that "abc" "def" are folded at compile time,
then the same guarantees can be specified for "abc" ~ "def". I can't
see a problem.
While it is not part of the spec, I do see a problem. If it were added....
I have also compiled this code with DMD:
void main() {
string foo = "foo";
string bar = foo ~ "bar" ~ "baz";
}
Resulting asm, no optimizations:
L0: push EBP
mov EBP,ESP
mov EDX,FLAT:_DATA[0Ch]
mov EAX,FLAT:_DATA[08h]
push dword ptr FLAT:_DATA[01Ch]
push dword ptr FLAT:_DATA[018h]
push dword ptr FLAT:_DATA[02Ch]
push dword ptr FLAT:_DATA[028h]
note 6 things
push EDX
push EAX
push 3
mov ECX,offset FLAT:_D11TypeInfo_Aa6__initZ
push ECX
call near ptr __d_arraycatnT
xor EAX,EAX
add ESP,020h
pop EBP
ret
Resulting asm, with optimizations:
L0: sub ESP,0Ch
mov EAX,offset FLAT:_D11TypeInfo_Aa6__initZ
push dword ptr FLAT:_DATA[01Ch]
push dword ptr FLAT:_DATA[018h]
push dword ptr FLAT:_DATA[02Ch]
push dword ptr FLAT:_DATA[028h]
push dword ptr FLAT:_DATA[0Ch]
push dword ptr FLAT:_DATA[08h]
again 6 things
push 3
I think that is a varargs call
push EAX
call near ptr __d_arraycatnT
add ESP,020h
add ESP,0Ch
xor EAX,EAX
ret
I can see just one arraycatn, so the two string literals are folded at
compile time, I think.
Bye,
bearophile
I think that DMD does some optimization for a~b~c etc. so that there is only
one call for any number of chained ~ (array cat n). In this case I think
it is doing that.
