On Thursday, 24 June 2021 at 14:06:11 UTC, seany wrote:
void f() { a[] * rd;// DO SOME WORK HERE .... this.dataSet = & rd_flattened; rd = cast (a [] *) dataSet;write("length of rd is : "); writeln((*rd).length); // <--- this works..// do some work on rd this.dataSet = rd; rd = cast (field.rawData [] *) dataSet; write("length of rd for a second time is : "); writeln((*rd).length); // <--- this ALSO works.. } Now outside `f`, in the same class, i call : void f2() { f(); a[] *aa ;aa = cast (a [] *) this.dataSet; // recall dataset is public global // if i print the address of this.dataSet here, this is the same as inside f() write("after calling f, count is: "); writeln((*aa).length); readln(); // here the situation completely blows up . the length is wrong.}
What is causing this issue ?
Your variable `a[] rd_flattened;` is a local variable to function `f()` allocated on the stack. Stack memory expires as soon as you return from the function. What `f2()` accesses through your global variable is a dangling pointer, a pointer to the expired stackframe of `f()`, which is why the `.length` is garbage.
