https://issues.dlang.org/show_bug.cgi?id=20722

Rainer Schuetze <r.sagitario@gmx.de> changed:

           What    |Removed                     |Added
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                 CC|                            |r.sagitario@gmx.de

--- Comment #1 from Rainer Schuetze <r.sagitario@gmx.de> ---
This is as safe/unsafe as any null pointer:

struct S { int a, b; }
void main() @safe
{
    S* s;
    s.b = 3;
}

null pointer accesses and anything in the vicinity are not considered a safety problem because they are supposed to cause an access violation, not a memory corruption.

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https://issues.dlang.org/show_bug.cgi?id=20722

--- Comment #2 from Mathias LANG <pro.mathias.lang@gmail.com> ---
Not quite. It's true the `null` pointers are not considered unsafe, otherwise we wouldn't be able to dereference anything in `@safe` code.

But one of the guarantee that `@safe` code offers is that you cannot create an invalid, non null pointer. That's why, for example, you can't do `arr.ptr`, but you can do `&arr[idx].ptr`.

And if you do:
```
    const void* ptr = &typeid(int).initializer()[$-1];
    assert(ptr !is null);
    writeln(ptr);
```

You create a pointer with value `0x3`, which breaks `@safe`.

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https://issues.dlang.org/show_bug.cgi?id=20722

--- Comment #3 from Rainer Schuetze <r.sagitario@gmx.de> ---
As my example tried to demonstrate, you can do this with a null pointer to
struct (or class) aswell:

import std.stdio;
struct S { int a, b; }
void main() @safe
{
    S* s;
    int* p = &s.b;
    writeln(p); // 4
    *p = 3;     // segfault
}

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https://issues.dlang.org/show_bug.cgi?id=20722

Mathias LANG <pro.mathias.lang@gmail.com> changed:

           What    |Removed                     |Added
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           See Also|                            |https://issues.dlang.org/sh
                   |                            |ow_bug.cgi?id=20725

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https://issues.dlang.org/show_bug.cgi?id=20722

--- Comment #4 from Mathias LANG <pro.mathias.lang@gmail.com> ---
I see what you mean now.
Yes indeed, you can do this with null pointer and struct, but it seems like a
bug too.
Filed as https://issues.dlang.org/show_bug.cgi?id=20725

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https://issues.dlang.org/show_bug.cgi?id=20722

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
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           Priority|P1                          |P3

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