[Issue 5690] New: Struct const member makes struct const

Mar 03, 2011

Tom

Mar 03, 2011

Stewart Gordon

Jan 24, 2012

Jan 24, 2012

Jan 24, 2012

Jan 24, 2012

March 03, 2011

[Issue 5690] New: Struct const member makes struct const

Posted by Tom

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Tom

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http://d.puremagic.com/issues/show_bug.cgi?id=5690

           Summary: Struct const member makes struct const
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: tarossi@gmail.com


--- Comment #0 from Tom <tarossi@gmail.com> 2011-03-03 05:34:25 PST ---
int main(string[] args) {
    auto s1 = f(); // MH MH
    auto s2 = g(); // OK
    s2.c = null; // OK
    return 0;
}

class C {}

struct StructWithConstMember {
    this(int i, C c) { this.i=i; this.c=c; }
    int i;
    const(C) c;
}

struct StructWithoutConstMember {
    this(int i, C c) { this.i=i; this.c=c; }
    int i;
    C c;
}

ref StructWithConstMember f() {
    return * new StructWithConstMember(1, new C); // ERROR
}

ref StructWithoutConstMember g() {
    return * new StructWithoutConstMember(1, new C); // OK
}


src\main.d(27): Error: *new StructWithConstMember(1,new C) is not mutable

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http://d.puremagic.com/issues/show_bug.cgi?id=5690 Stewart Gordon <smjg@iname.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |spec CC| |smjg@iname.com --- Comment #1 from Stewart Gordon <smjg@iname.com> 2011-03-03 07:24:09 PST --- It only makes sense that it should make it const - to reassign the struct would violate the constancy of the const member. Though the MBNR approach (see issue 2625) would also work. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=5690 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED CC| |bugzilla@digitalmars.com Resolution| |INVALID --- Comment #2 from Walter Bright <bugzilla@digitalmars.com> 2012-01-24 00:06:54 PST --- Right, this is not a compiler bug. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=5690 Kenji Hara <k.hara.pg@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|INVALID | --- Comment #3 from Kenji Hara <k.hara.pg@gmail.com> 2012-01-24 05:20:27 PST --- (In reply to comment #2) > Right, this is not a compiler bug. No, this is a compiler bug. (In reply to comment #1) > It only makes sense that it should make it const - to reassign the struct would violate the constancy of the const member. A returned value from f() is *mutable* object, so to reassign the part of it is still valid. f().i = 10; // field i is mutable so this code should compile. This issue is a dup of bug 6366, that has more better summary "Issue 6336 - Can't return ref T where T has const/immutable members". -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=5690 --- Comment #4 from Kenji Hara <k.hara.pg@gmail.com> 2012-01-24 05:22:57 PST --- Notice: A NewExpression like (new StructWithConstMember(1, new C)) makes rvalue, but dereferencing it (* new StructWithConstMember(1, new C)) makes *lvalue*. So returning it from function by ref is valid. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

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