[Issue 10970] Segfault in a simple test compiled without -g.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10970


monarchdodra at gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |monarchdodra at gmail.com


--- Comment #6 from monarchdodra at gmail.com 2013-09-06 02:10:45 PDT ---
(In reply to comment #5)
> Crashes on win32 as well.

If I recall correctly, I think the problem is "simply" that AA has *very* bad
support for types with elaborate CC, and destruction. Take this "simple" use
case:

//####
import std.stdio;

int count;

struct S
{
    this(int){++count; writeln("construction");}
    this(this){assert(0);} //never called
    ~this(){--count; writeln("destruction");}
}

void main()
{
    S[int] aa;
    writeln("----");
    aa[5] = S(3);
    writeln("----");
    aa.remove(5);
    writeln("----");
    assert(aa.length == 0);
    assert(count >= 0); //Fails here
}
//####
----
construction
destruction
destruction
----
----
//####

In just this little snippet, there are *all* kinds of wrong:
1. insertion: when inserting a new item, CC ("this(this)") is never called for
some strange reason. Furthermore, destruction happens *twice* (again, for some
strange reason).
2. removal: Where's the destructor?

These use cases are probably reported already, you are experiencing the results
of these defects.

Long story short, at the end of the day, your array is "over-destroyed". Given
that AA is a *strongly* relies on reference counting to provide deterministic
behavior, things simply don't go well.

A lot of work is being done on fixing AAs (AFAIK), but don't expect it to be
fixed any time soon.

As a workaround, you could try using slices instead of AA's?

//----
import std.stdio;

class A
{
    this(string name)
    {
        m[name] = Arr.init;
    }

    alias A[] Arr;
    Arr[string] m;
}

int main()
{
    A a = new A("test");
    return 0;
}
//----

In particular, "A" is a class, so it can't have a destructor (in the sense that
a *reference* doesn't get destroyed). As such, there is minimal use to keeping
an Array over a slice.

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