Thread overview
[Issue 22215] returning expired stack pointers in @system code allowed by spec, not by implementation
Aug 16
Aug 25
August 16

Dennis <> changed:

           What    |Removed                     |Added
                 CC|                            |
           Hardware|x86                         |All
            Summary|[dip1000] scope analysis    |returning expired stack
                   |does not respect @system or |pointers in @system code
                   |@trusted                    |allowed by spec, not by
                   |                            |implementation
           Severity|major                       |normal

--- Comment #1 from Dennis <> ---
It doesn't compile without -dip1000 either, the error predates it.

> this workaround should not be required.

Intentionally returning an expired stack pointer should be a very rare occurrence, I think a workaround is warranted. However, the spec says:

> @system functions may perform any operation legal from the perspective of the language including inherently memory unsafe operations like returning pointers to expired stackframes

So at least one has to change: the implementation, or the spec.

August 25

--- Comment #2 from Ate Eskola <> ---
There appears to be two bugs, one in vanilla DMD and one with -dip1000.

As Dennis said, my initial example fails to compile regardless of the compiler switches used. But there is a watered-down version of my workaround:

int* f()
{ int x = 42;
  auto wannaBePointer = &x;
  return wannaBePointer;

This one compiles with vanilla DMD, but the -dip1000 bug prevents compiling it with the said flag.

The full workaround in the initial example still compiles with the flag too.

August 25

--- Comment #3 from Dennis <> ---
(In reply to Ate Eskola from comment #2)
> There appears to be two bugs, one in vanilla DMD and one with -dip1000.

That's right, the latter one is