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Align to struct alignment before entering struct.

	Structs may have different alignments from their first
	element, so if we don't align on entry, we can be reading
	things at the wrong offset.

	Fixes #88

--- a/lib/std/varargs.myr

+++ b/lib/std/varargs.myr

@@ -55,14 +55,29 @@

 extern const put	: (fmt : byte[:], args : ... -> size)

 const vaenter = {ap

-	match typedesc(vatype(ap))

+	var ty

+

+	ty = vatype(ap)

+	match typedesc(ty)

 	| `Tyslice enc:	-> [.args=sliceptr(ap.args), .tc=[.nelt=slicelen(ap.args), .rem=enc, .isiter=false]]

 	| `Tytuple tc:	-> [.args=ap.args, .tc=tc]

-	| `Tystruct tc:	-> [.args=ap.args, .tc=tc]

+	| `Tystruct tc:	-> [.args=cursoralign(ap.args, ty), .tc=tc]

 	| `Tyarray (sz, enc):	-> [.args=ap.args, .tc=[.nelt=sz, .rem=enc, .isiter=false]]

 	| `Tyname (name, enc):	-> [.args=ap.args, .tc=typeenccursor(enc)]

 	| _:	std.die("unable to enter type\n")

 	;;

+}

+

+const cursoralign = {arg, ty

+	var ti, align, p

+

+	ti = typeinfo(ty)

+

+	/* apply the alignment to the arg pointer */

+	align = ti.align castto(intptr)

+	p = arg castto(intptr)

+	p = (p + align - 1) & ~(align - 1)

+	-> p castto(byte#)

 }

 const vaenterunion = {ap, elt