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digitalmars.D.bugs - [Issue 6681] New: bogus duplicate union initialization or overlapping initialization errors

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6681

           Summary: bogus duplicate union initialization or overlapping
                    initialization errors
           Product: D
           Version: D1 & D2
          Platform: Other
        OS/Version: Mac OS X
            Status: NEW
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: fawzi gmx.ch



In D1 code like this

{{{

module t;

template MTuple( TList... )
{
    alias TList MTuple;
}

struct V{
    union {
        double[2] cell;
        version(v2) {} else {
            MTuple!(double,double) tuple;
        }
        struct {
            union { double x; double r; }
            union { double y; double g; }
        }
    }

    static const V zero={x:0, y:1};
}

V a=V.zero;

version(v2) {
struct Q {
    union {
        struct {
            double x, y;
        }
        V xyzw;
    }

    const static Q id = { x: 0, y:1 };

}

Q b=Q.id;
}
}}}

fails with duplicate union initialization, which is incorrect.
This happens both with and without -version=v2 which shows that the error is
not just the tuple.
Closely related errors are present also in D2, even if one uses constructors:
{{{

module t;

template MTuple( TList... )
{
    alias TList MTuple;
}

struct V{
    this(double a,double b){
        x=a;
        y=b;
    }
    union {
        double[2] cell;
        version(v2) {} else {
            MTuple!(double,double) tuple;
        }
        struct {
            union { double x; double r; }
            union { double y; double g; }
        }
    }

    static immutable V zero=V(0,1);
}

V a=V.zero;

version(v2) {
struct Q {
    union {
        struct {
            double x, y;
        }
        V xyzw;
    }

    immutable static Q id =Q(0,1);

}

Q b=Q.id;
}
}}}

similar errors seem to be very old:

http://www.digitalmars.com/d/archives/digitalmars/D/bugs/6271.html
and there are related or very similar errors are already present in bugzilla:

http://d.puremagic.com/issues/show_bug.cgi?id=4241 which basically uses the
same code as me (omg derived vector structs), but just complains about line
number, seemingly accepting the error (which is bogus imho.
I have also tried to sprinkle around some =void but I just managed to end up
with "Error: no initializer for union".

http://d.puremagic.com/issues/show_bug.cgi?id=1432 (using initializers in the
union)

but this one at least with D1 is a regression from 1.067 at least

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Sep 16 2011
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6681


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com



20:57:25 PDT ---
There have been several patches to 'fix' struct/union initialization.
Evidently, we need to step back a bit and rethink/reengineer it. Something
along the lines of:

1. Create a list of all the fields, in lexical order. Each field will have a
beginning offset and an ending offset. One field 'overlaps' another if its
offset range overlaps the other.

2. Examine list of initializers. Unnamed initializers will be associated with a
field as follows:
    1. if it's the first initializer, it's the first field. Done.
    2. start with the previous field that was initialized. Move forward through
    the field list and pick the first field that does not overlap with that
    previous field. That will be the field associated with that initializer.

3. If any initialized field overlaps with any other initialized field, error.

4. Go back through the field list again, in order. If a field does not have an
initializer, and does not overlap with any other initialized field, assign it
the default initializer.

At this point, I wish to defer this to the next update.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yebblies gmail.com



Ok, the first test case reduces to this:

struct V{
    union {
        double[2] cell;
        double x;
    }

    static immutable V zero=V(0,1);
}

The problem being that the struct literal gets turned into:
  this(a, b) { cell = 0; x = 1; }
ie. it passes the first argument to the first member, and the second argument
to the second.

This is sort of what I'd expect to happen, but the error message is completely
valid for what it's trying to do.  If anyone has a better idea of how struct
literals should map to unions, please open another bug report about it.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Platform|Other                       |All
            Summary|bogus duplicate union       |struct constructor call is
                   |initialization or           |converted to struct literal
                   |overlapping initialization  |that breaks union
                   |errors                      |initialization
         OS/Version|Mac OS X                    |All



Got my test cases a little mixed up there, but it's still mostly valid.

All of the non-struct-literal struct construction seems to be converted into
struct literals.  eg.

struct S
{
    this(int a, int b) { this.a = b; this.b = a; }
    union {
        ulong g;
        struct {int a, b; };
    }
}

static immutable S s = S(0, 1);

Prints: (with a little extra debug output)

StructLiteralExp::semantic('S(0LU,1,0)')
        S
Error: duplicate union initialization for a
Error: duplicate union initialization for b

As you can see, it make a struct literal with every field accounted for.

So this is a bug in the constfolding/ctfe code.

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Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au





 As you can see, it make a struct literal with every field accounted for.
 
 So this is a bug in the constfolding/ctfe code.


Not exactly. It's a compiler structural problem: there's no way to specify a
struct literal with missing fields. Struct static initializers can do it, but
struct literals cannot.

I think the solution is to merge struct literals with struct static
initializers, as it says in a TODO in the code.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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 Not exactly. It's a compiler structural problem: there's no way to specify a
 struct literal with missing fields. Struct static initializers can do it, but
 struct literals cannot.
 
 I think the solution is to merge struct literals with struct static
 initializers, as it says in a TODO in the code.


One of the D1 cases seems to have the same problem with struct static
initializers.  Can't this be done by just nulling out the untouched fields in
the Expressions array and ensuring at least one field gets initialized?

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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 Not exactly. It's a compiler structural problem: there's no way to specify a
 struct literal with missing fields. Struct static initializers can do it, but
 struct literals cannot.
 
 I think the solution is to merge struct literals with struct static
 initializers, as it says in a TODO in the code.


 
 One of the D1 cases seems to have the same problem with struct static
 initializers.  Can't this be done by just nulling out the untouched fields in
 the Expressions array and ensuring at least one field gets initialized?


Maybe. The order of fields in a struct is fixed, so in theory that ought to
work.
It's a while since I last looked at it, but I remember there were severe
problems with anonymous unions nested inside anonymous unions. There's code
elsewhere in the compiler which tries to identify fields based on their type +
offset, but that cannot work. It appears to work at the moment, but only
because it assumes when fields are initialized in order with no gaps.
Still, I've fixed some of those compiler bugs recently, so maybe it's more
possible now.

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Ok, I'll take a look at it tomorrow unless you want it.  I know there are at
least two places it checks for overlapping union initialization, one in
expression.c and one somewhere in the glue, maybe e2ir?

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 Ok, I'll take a look at it tomorrow unless you want it.  I know there are at
 least two places it checks for overlapping union initialization, one in
 expression.c and one somewhere in the glue, maybe e2ir?


The big one is in init.c. Around line 340 there's code I wrote (to replace the
code in 320..340). Walter disabled that code a bit later, but he didn't say
why. 

Would be great if you could take a fresh look at it.

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yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
         AssignedTo|nobody puremagic.com        |yebblies gmail.com



I think for this to work, the interpreter needs to be able to handle
uninitialized values, and unions need to default to void initializers.  I have
a patch for this that is nearly ready, and solves issue 6438 at the same time.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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21:30:50 PST ---

It's a compiler structural problem: there's no way to specify a


struct literal with missing fields.

I don't know about in CTFE, but in the rest of the compiler the code is in
place to just have elements[i] be NULL for missing fields.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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It's a compiler structural problem: there's no way to specify a


 struct literal with missing fields.
 
 I don't know about in CTFE, but in the rest of the compiler the code is in
 place to just have elements[i] be NULL for missing fields.


I have branch for this that mostly works, but no time to work on it at the
moment.

https://github.com/yebblies/dmd/tree/ctfeunion

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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https://github.com/D-Programming-Language/phobos/pull/493
and then
https://github.com/D-Programming-Language/dmd/pull/803

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Mar 13 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Thanks for doing this.  I think my branch was still letting you return
partially uninitialized arrays/structs from ctfe.  I also think the following
should work:

union U
{
   int a, b;
}
int func()
{
   U u;
   u.a = 3;
   assert(u.b == 3);
   return 1;
}
static assert(func());

But I don't know how to implement it. (it might not be worth it)

Umm, test cases. (some pass, some fail, some pulled out of other test cases in
dmd/phobos.)  The last one should fail, I doubt it's useful leave a variable
partially initialized.


/*
version(none)
{
    struct S
    {
        this(int a, int b) { this.a = b; this.b = a; }
        union {
            ulong g;
            struct
            {
                int a;
                int b;
            }
        }
    }

    static immutable S s = S(1, 0);

    extern(C) int printf(const char *, ...);

    void main()
    {
        S s = .s;
        printf("%d %d %d\n", s.g, s.a, s.b);
    }
}

version(none)
{
    union in6_addr
    {
        private union _in6_u_t
        {
            ubyte[16] u6_addr8;
            ushort[8] u6_addr16;
            uint[4] u6_addr32;
        }
        _in6_u_t in6_u;

        ubyte[16] s6_addr8;
        ushort[8] s6_addr16;
        uint[4] s6_addr32;

        alias s6_addr8 s6_addr;
    }


    const in6_addr IN6ADDR_ANY = { s6_addr8: [0] };
}


version(none)
{
    struct Zadok
    {
        char [4] s = void;
    }

    int quop()
    {
        Zadok pong;
        pong.s = ['z','x','f', 'g'];
        return 1;
    }

    static assert(quop()==1);
    static assert(quop()==1); // check for clobbering
}


//version = testc;
version(testc)
{
    union U
    {
        int a;
        int b;
    }

    int testxx()
    {
        U u;
        u.a = 7;
        u.b = 4;
        assert(u.a == 7);
        assert(u.b == 4);
        return 1;
    }

    static assert(testxx());
}

//version = testb;
version(testb)
{
    void fillWithZero(T)(T[] arr)
    {
        foreach(ref x; arr)
            x = 7;
    }

    T[4] f(T)()
    {
        T[4] stackSpace = void;
        T[4] x = stackSpace;
        int y = x[0];
        //int z = y + y;
        fillWithZero(stackSpace[]);
        return stackSpace;
    }

    static assert(f!int() == [7,7,7,7]); 
}

//version = testa;
version(testa)
{
    interface SomeInterface
    {
      int daz();
      float bar(char);
      int baz();
    }

    interface SomeOtherInterface
    {
        int xxx();
    }

    class TheBase : SomeInterface, SomeOtherInterface
    {
        int q = 88;
        int rad = 61;
        int a = 14;
        int somebaseclassfunc() { return 28;}
        int daz() { return 0; }
        int baz() { return 0; }
        int xxx() { return 762; }
        int foo() { return q; }
        float bar(char c) { return 3.6; }
    }

    class SomeClass : TheBase, SomeInterface
    {
        int gab = 9;
        int fab;
        int a = 17;
        int b = 23;
        int foo() { return gab + a; }
        float bar(char c) { return 2.6; }
        int something() { return 0; }
        int daz() { return 0; }
        int baz() { return 0; }
    }

    class Unrelated : TheBase {
        this(int x) { a = x; }
    }

    auto classtest1(int n)
    {
        SomeClass c = new SomeClass;
        assert(c.a == 17);
        assert(c.q == 88);
        TheBase d = c;
        assert(d.a == 14);
        assert(d.q == 88);
        if (n==7)
        {   // bad cast -- should fail
            Unrelated u = cast(Unrelated)d;
            assert(u is null);
        }
        SomeClass e = cast(SomeClass)d;
        d.q = 35;
        assert(c.q == 35);
        assert(c.foo() == 9 + 17);
        ++c.a;
        assert(c.foo() == 9 + 18);
        assert(d.foo() == 9 + 18);
        d = new TheBase;
        SomeInterface fc = c;
        SomeOtherInterface ot = c;
        assert(fc.bar('x') == 2.6);
        assert(ot.xxx() == 762);
        fc = d;
        ot = d;
        assert(fc.bar('x') == 3.6);
        assert(ot.xxx() == 762);

        Unrelated u2 = new Unrelated(7);
        assert(u2.a == 7);
        return 6;
    }
    static assert(classtest1(1));
    static assert(classtest1(2));
    static assert(classtest1(7)); // bug 7154
}

//version = testd;
version(testd)
{
    struct XY { union { int x, y; } }
    struct AHolder {
        XY aa;
        void a(XY x) { aa = x; }
    }
    struct AB {
        AHolder aHolder;
        XY b;
        void a(XY x) { aHolder.a(x); }
    }
    struct Main {
        AB ab;

        void setB() { ab.b = XY(); }
        void f() {
            ab.a(XY.init);
            setB();
        }
    }
}

//version = teste;
version(teste)
{
    union U
    {
        int a;
        long b;
    }

    long test()
    {
        U u;
        u.a = 3;
        u.b = 8;
        return u.a + u.b;
    }

    static assert(test() == 11);
}

//version = testf;
version(testf)
{
    int[5] test()
    {
        int[5] var = void;
        var[0] = 6;
        var[2] = 6;
        var[4] = 6;
        return var;
    }
    pragma(msg, test());
}
*/

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Mar 13 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Commit pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/7cecf0090f7d22caf0efd2e1a558171013a387a5


Supplemental change required by regression bug 6681

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Mar 14 2012
prev sibling parent d-bugmail puremagic.com writes:
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Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/296b99db347ace5e166120564146277788957eaf


Fix issue 6681 - struct constructor call is converted to struct literal ...

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