OK, it looks like -fno-strict-aliasing is here to stay. Casting freely between pointers to different types is pervasive in the source code, and there's insufficient discipline in the culture to try to fix it. And I'm not volunteering. static void pd_arrayof_conjoint_jlongs(const HeapWord* from, HeapWord* to, size_t count) { #ifdef AMD64 _Copy_arrayof_conjoint_jlongs(from, to, count); #else pd_conjoint_jlongs_atomic((const jlong*)from, (jlong*)to, count); #endif // AMD64 } static void pd_arrayof_conjoint_oops(const HeapWord* from, HeapWord* to, size_t count) { #ifdef AMD64 assert(BytesPerLong == BytesPerOop, "jlongs and oops must be the same size"); _Copy_arrayof_conjoint_jlongs(from, to, count); #else pd_conjoint_oops_atomic((const oop*)from, (oop*)to, count); #endif // AMD64 } On Fri, Aug 10, 2018 at 5:59 AM, Andrew Haley <aph@redhat.com> wrote:

On 08/08/2018 08:51 PM, Martin Buchholz wrote:

...

I'd like to see hotspot stop using the -fno-strict-aliasing curtch, replacing it with union and/or may_alias, but this is a serious investment.

It's a serious investment, and we'd risk breaking stuff. At least the entire heap would have to be an array with elements which are a union of all of the possible types, and there'd be a byte array overlaid on top of that. It would not be pretty.