cannot compile createRC with custom dtor class

[ShigekiKarita]

When I inserted custom dtor ~this() nothrow {} to the existing class in unittest, it failed.

mir-algorithm/source/mir/rc/ptr.d

Lines 248 to 253 in c316ed2

	static class C : D, I
	{
	double value;
	ref double bar() @safe pure nothrow @nogc { return value; }
	this(double d) { value = d; }
	}

dub test
Generating test runner configuration 'mir-algorithm-test-default' for 'default' (library).
Excluding package.d file from test due to https://issues.dlang.org/show_bug.cgi?id=11847
Excluding package.d file from test due to https://issues.dlang.org/show_bug.cgi?id=11847
Excluding package.d file from test due to https://issues.dlang.org/show_bug.cgi?id=11847
Excluding package.d file from test due to https://issues.dlang.org/show_bug.cgi?id=11847
Excluding package.d file from test due to https://issues.dlang.org/show_bug.cgi?id=11847
Performing "unittest" build using /home/karita/dlang/dmd-2.087.0/linux/bin64/dmd for x86_64.
mir-core 0.3.5: target for configuration "library" is up to date.
mir-algorithm 3.5.0-alpha11: building configuration "mir-algorithm-test-default"...
Warning: multivariate cubic spline with derivatives was not tested!!!
Warning: multivariate cubic spline with derivatives was not tested!!!
source/mir/type_info.d(72,29): Error: function object.destroy!(true, C).destroy is not nothrow
source/mir/type_info.d(59,21): Error: nothrow function mir.type_info.mir_get_type_info!(C).mir_get_type_info.destroy_impl may throw
source/mir/rc/ptr.d(128,42): Error: template instance `mir.type_info.mir_get_type_info!(C)` error instantiating
source/mir/rc/ptr.d(225,27):        instantiated from here: __ctor!int
source/mir/rc/ptr.d(256,24):        instantiated from here: createRC!int
/home/karita/dlang/dmd-2.087.0/linux/bin64/dmd failed with exit code 1.

I do not know why this happened because everything seems to be nothrow.

• destroy is ok because it is template just calling rt_finalize https://github.com/dlang/druntime/blob/3ba98e659dc6857d7f5ad6383adc2b02510ce597/src/object.d#L628
• rt_finalize is also nothrow https://github.com/dlang/druntime/blob/8a5e6f2fe878d9470a39ebee2574892370af5e01/src/rt/lifetime.d#L1423

@9il Do you have any idea or workaround to call createRC with the class having custom dtor?

[ShigekiKarita]

I found the bug in the object. It seems to have the wrong declaration here.
https://github.com/dlang/druntime/blob/3ba98e659dc6857d7f5ad6383adc2b02510ce597/src/object.d#L990-L991

[ShigekiKarita]

I also found the workaround for this bug. We can put the correct declaration in mir/type_info.d and directly call rt_finalize as same as destroy.

[9il]

DRuntiem Issue https://issues.dlang.org/show_bug.cgi?id=20049

[9il]

All destructors that are used in Mir RC types should be nothrow. In the same time, there is no warranty that common D destructor is nothrow, this is why rt_finalize does not have any attributes.

As a workaround for this DRuntieme issue, I would suggest marking all user classes and interfaces with extern(C++) and optionally their members as extern(D):. Then the destroy function would not use rt_finalize

[ShigekiKarita]

I see. Because throwing an exception in dtor is unsafe for unwinding stack, the rt_finalize converts exceptions to FinalizeError. So I think rt_finalize can be nothrow.

Thanks to your workaround, my use case seems to be working.