[Bug target/79671] [7 Regression] mapnik miscompilation on armv7hl since r235622

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671

--- Comment #24 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
(In reply to Richard Biener from comment #23)
> (In reply to Bernd Edlinger from comment #22)
> > (In reply to Jakub Jelinek from comment #20)
> > > which fails also on x86_64-linux at -O2.  And that testcase regressed with
> > > r223126.  Now whether this is valid C++, no idea, placement new is messy.
> > 
> > This test case can't be valid, suppose the A has a copy constructor
> > that that is also not called when B is moved around.
> 
> The canonical fix is to put the type you placement new into the union storage
> into the union as regular member rather than having a char[] member in the
> union.

Yes. Of course you cannot put a non-POD type in a union,
but maybe a pointer to A, that is probably what boost should
do in their functor class.