[x86] segmentation fault with aligned struct parameters

[the-horo]

I'm not 100% sure if the title is the real cause but the following code crashes:

align(8) struct Cent { }

void udivmod(Cent, int) { }

void main (){
    udivmod(Cent(), 0);
}

It's a reduction from this line in the int128 unittest.

dmd and gdc don't fail. I've only hit this on x86.

[kinke]

This is a duplicate of #1356; see in particular #1356 (comment).

[kinke]

You do have this existing workaround, right?

ldc/runtime/druntime/src/core/int128.d

Lines 37 to 40 in e170ca5

	version (X86_64) private enum Cent_alignment = 16;
	// 32-bit x86: need default alignment due to https://github.com/ldc-developers/ldc/issues/1356
	else version (LDC_X86) private enum Cent_alignment = U.alignof;
	else private enum Cent_alignment = (size_t.sizeof * 2);

[the-horo]

That's in druntime, I was hitting it in

ldc/dmd/common/int128.d

Lines 23 to 27 in e170ca5

	align(16) struct Cent
	{
	U lo; // low 64 bits
	U hi; // high 64 bits
	}

which I found out by running ldc2-unittest on x86 when compiling with another ldc2 installation.

[kinke]

Ah okay, that 'copy'. It's unused, except for ldc2-unittest.

[the-horo]

Alright then, if it's unused and the underlying issue was already reported then I can ignore it. Thank you again for your help.