Bug 4790 – Wrong code when updating struct member value from fiber

This is a test case produced from an experiment with converting opApply to ranges using fibers: import core.thread, std.traits, std.range, std.stdio; struct OpApplyToRange(Iterable) { Fiber fiber; ForeachType!Iterable _front; Iterable iterable; void doLoop() { stderr.writeln("_front's address from fiber: ", &_front); foreach(elem; iterable) { stderr.writefln("Assigning %s to front", elem); _front = elem; stderr.writeln("_front has value ", _front); Fiber.yield(); stderr.writeln("Resumed with value ", _front); } stderr.writeln("doLoop done."); } this(Iterable iterable) { this.iterable = iterable; fiber = new Fiber(&doLoop); fiber.call(); } void popFront() { fiber.call(); } } void main() { auto oar = OpApplyToRange!(int[])([1,2,3]); stderr.writeln("_front's address from main: ", &oar._front); foreach(i; 0..3) { stderr.writeln("Calling fiber sees: ", oar._front); oar.popFront(); } } _front's address from fiber: 18FE34 Assigning 1 to front _front has value 1 _front's address from main: 18FE24 Calling fiber sees: 1 Resumed with value 1 Assigning 2 to front _front has value 2 Calling fiber sees: 1 Resumed with value 2 Assigning 3 to front _front has value 3 Calling fiber sees: 1 Resumed with value 3 doLoop done. Apparently the same variable somehow has a different address when viewed from the main thread vs. fron a fiber, leading to some rather interesting consequences, like updates made from the fiber not being visible in the main function. (??????????)

(Slaps self in forehead.) Duh, of course. When I take the address of doLoop() it's taking the address of a stack variable. Of course this isn't going to work. It needs to be a class.