can break immutable with postblit

[dlangBugzillaToGithub]

ag0aep6g reported this on 2018-02-02T11:58:46Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=18357

CC List

• Ate Eskola
• Andrei Alexandrescu (@andralex)
• Ketmar Dark

Description

----
struct S
{
    int* x;
    this(this) @safe { *x = 13; }
}

void main() @safe
{
    immutable int* x = new int(42);
    assert(*x == 42); /* passes */
    auto s = immutable S(x);
    auto s2 = s; /* should be rejected */
    assert(*x == 42); /* fails */
}
----

[dlangBugzillaToGithub]

ag0aep6g commented on 2018-03-06T12:56:29Z

*** Issue 18561 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

andrei (@andralex) commented on 2018-03-19T15:57:47Z

A similar example shows fetching a mutable pointer to immutable data:

----
int* g;

struct S
{
    int* x;
    this(this) { g = x; }
}

void main()
{
    immutable int* x = new int(42);
    assert(*x == 42); /* passes */
    auto s = immutable S(x);
    auto s2 = s; /* should be rejected */
}

[dlangBugzillaToGithub]

dfj1esp02 commented on 2018-04-03T07:45:44Z

Postblit should respect type qualifiers the same way const constructor does.