dtor / destructor not called for (rvalue) struct used in opApply

[dlangBugzillaToGithub]

Marco Leise (@mleise) reported this on 2013-06-18T16:09:26Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=10409

CC List

• Iain Buclaw (@ibuclaw)

Description

This code

--- 8< ---------------

import core.stdc.stdio;

struct DestroyMe
{
	~this() { printf("~this() called
"); }

	int opApply(in int delegate(int item) dg)
	{
		throw new Exception("Here we go!");
	}
}

void main()
{
	printf("Version with no dtor call:
");
	try {
		foreach (item; DestroyMe()) {}
	} catch {}
	printf("Version with dtor call:
");
	try {
		auto lvalue = DestroyMe();
		foreach (item; lvalue) {}
	} catch {}
}

--- >8 --------------

prints:
Version with no dtor call:
Version with dtor call:
~this() called

So the dtor call gets missed when the struct's scope is inside the foreach header. There is another open bug about struct destructors not being called on out parameters:
http://d.puremagic.com/issues/show_bug.cgi?id=6186

[dlangBugzillaToGithub]

k.hara.pg commented on 2013-07-07T23:13:36Z

I couldn't reproduce the issue on Windows7, by using release-dmd versions from 2.058 to 2.063.2. What version do you use?

[dlangBugzillaToGithub]

Marco.Leise commented on 2013-07-08T02:54:27Z

(In reply to comment #1)
> I couldn't reproduce the issue on Windows7, by using release-dmd versions from
> 2.058 to 2.063.2. What version do you use?

I was using GDC and LDC. It really doesn't happen with DMD. I'll mark this as invalid and open new reports for the other compilers. Thanks for looking into this anyway!

[dlangBugzillaToGithub]

ibuclaw (@ibuclaw) commented on 2013-07-08T11:34:09Z

From the backend's perspective, the frontend represents the code in this way:

try
{
    DestroyMe __sl5;
    DestroyMe.opApply (&__sl5, {.object=0B, .func=__foreachbody6});
    apply.DestroyMe.~this (&__sl5);
}
catch (struct Throwable &)
{
}


try
{
    struct DestroyMe lvalue;

    try
    {
        DestroyMe.opApply (&lvalue, {.object=0B, .func=__foreachbody8});
    }
    finally
    {
        apply.DestroyMe.~this (&lvalue);
    }
}
catch (struct Throwable &)
{
}


In this instance, you could either say that it is the job of the backend to wrap ExpDtorStatement's in try{} finally{} blocks, or fix the frontend to generate a matching representation.

[dlangBugzillaToGithub]

ibuclaw (@ibuclaw) commented on 2013-07-08T12:15:06Z

(In reply to comment #3)
> In this instance, you could either say that it is the job of the backend to
> wrap ExpDtorStatement's in try{} finally{} blocks, or fix the frontend to
> generate a matching representation.

Hmmm... I meant Expression::toElemDtor.  :)