Bug 1648 – Casting a function literal to void* swallows the function or segfaults

When saving a delegate as a void* and only using one delegate from the same function, attempts to execute the delegate by casting to the original type do nothing. When saving multiple delegates from the same function, if any of them are cast to void*, a segmentation fault occurs. Casting is inherently dangerous, I know, but there's no other way to pass a delegate while ignoring its type.

Created attachment 204 a test case that shows the problem

Jarrett Billingsley wrote: > <[email protected]> wrote in message > news:[email protected]/issues/... >> http://d.puremagic.com/issues/show_bug.cgi?id=1648 >> >> Summary: Casting a function literal to void* swallows the >> function or segfaults >> Product: D >> Version: 2.007 >> Platform: PC >> OS/Version: Linux >> Status: NEW >> Severity: normal >> Priority: P2 >> Component: DMD >> AssignedTo: [email protected] >> ReportedBy: [email protected] >> >> >> When saving a delegate as a void* and only using one delegate from the >> same >> function, attempts to execute the delegate by casting to the original type >> do >> nothing. >> >> When saving multiple delegates from the same function, if any of them are >> cast >> to void*, a segmentation fault occurs. >> >> Casting is inherently dangerous, I know, but there's no other way to pass >> a >> delegate while ignoring its type. >> >> >> -- >> > > delegate.sizeof != (void*).sizeof. > > It's no real surprise that this doesn't work. Delegates are not simple > pointers; they are actually a struct with two members, but you shouldn't > really be relying on the underlying implementation in any way. > > What is it that you're trying to do, anyway? Delegates are strongly typed > for a reason -- the compiler can't generate the correct call sequence unless > it knows the exact type of the delegate. There's probably a much better way > of doing what you want. (delegate*).sizeof == (void*).sizeof The example casted the address of the delegate to void*. I tried using Variant.coerce to retrieve a boxed delegate, but that failed (delegates aren't numeric types, objects, or strings, and coerce only supports those). Now I've found that Variant.peek does support delegates, so I'm set.

As Jarrett Billingsley pointed out, the error was in my code: taking the address of a local variable.