On 6/13/18 10:43 AM, Michał wrote:
When I pass my struct to function something is going wrong. I don't know
how to fix it.
Code:
import std.stdio;
void print(ref Vector v, string s){
writefln("%s==%s %s", &v.x, v.ptr, s);
}
struct Vector {
int x;
int* ptr;
this(this) {
ptr = &x;
print(this, "postblit");
}
}
void someFunc(Vector t) {
print(t, "in someFunc");
}
void main() {
auto tmpA = Vector();
tmpA.ptr = &tmpA.x;
print(tmpA, "start");
someFunc(tmpA);
}
Result on my machine:
7FFF7D70BC00==7FFF7D70BC00 start
7FFF7D70BBF0==7FFF7D70BBF0 postblit
7FFF7D70BBD0==7FFF7D70BBF0 in someFunc
In the last line pointers are not matching. I thought that postblit will
do the thing but it is not the case. How to make 'ptr' to be null or
'&this.x' all the time?
D allows moving any struct instance without calling postblit, as long as
the original is no longer used.
The optimizer is likely seeing here that the memory can be copied
without calling postblit, because nobody is using tmpA after the call.
In general, you should NOT store an internal pointer in a struct, unless
you allocate it on the heap.
-Steve