PING: Could you review it?
http://cr.openjdk.java.net/~ysuenaga/JDK-8160354/webrev.01/
Yasumasa
On 2016/08/23 21:48, Yasumasa Suenaga wrote:
Hi Kim, and all,
Sorry for my late reply.
I've fixed them in new webrev. Could you review it?
http://cr.openjdk.java.net/~ysuenaga/JDK-8160354/webrev.01/
Also I need a sponsor.
Thanks,
Yasumasa
On 2016/06/28 12:43, Yasumasa Suenaga wrote:
Hi Kim,
On 2016/06/28 7:12, Kim Barrett wrote:
On Jun 27, 2016, at 10:29 AM, Yasumasa Suenaga <yasue...@gmail.com> wrote:
Hi all,
This review request relates to JDK-8160310: HotSpot cannot be built with GCC 6 .
I encountered 2 compiler warnings and 2 VM crashes when I compiled OpenJDK 9
with
GCC 6 on Fedora 24 x64.
I think these error should be fixed.
I uploaded webrev.
Could you review it?
http://cr.openjdk.java.net/~ysuenaga/JDK-8160354/webrev.00/
------------------------------------------------------------------------------
src/share/vm/c1/c1_Instruction.hpp
The problems here are similar to those JDK-8160357, e.g. casting
uninitialized memory to a pointer to class type and treating it as
such, without having first called the constructor. That's undefined
behavior.
The workaround is to use -fno-lifetime-dse when building with gcc 6.
The code to do that seems to have been broken though.
I can avoid this error with makefile fix in [1].
------------------------------------------------------------------------------
src/cpu/x86/vm/assembler_x86.cpp
191 RelocationHolder rspec = (disp_reloc == relocInfo::none)
192 ? RelocationHolder::none
193 : rspec =
Relocation::spec_simple(disp_reloc);
I have no idea what is being attempted by this change, but I really
doubt this is correct. The precedence of ?: is higher than the
precedence of =.
Sorry, I will fix.
I think I see what might be going wrong with the original code.
RelocationHolder has a _relocbuf member, which is really just storage
for a Relocation object. The constructors for RelocationHolder are
both problematic, but the no-arg constructor is the one at fault here.
RelocationHolder::RelocationHolder() {
new(*this) Relocation();
}
This is constructing a different object over the current, which is
undefined behavior, so gcc 6 is perhaps eliding it, leading to the
failure. What this should actually be doing is using the start of the
_relocbuf member as the placement new location.
I suspect this is another case that would have been suppressed by the
missing gcc6-specific build options.
For the record, the other constructor is
RelocationHolder::RelocationHolder(Relocation* r) {
// wordwise copy from r (ok if it copies garbage after r)
for (int i = 0; i < _relocbuf_size; i++) {
_relocbuf[i] = ((void**)r)[i];
}
}
and that comment is just wrong, since the actual object could have
been allocated close to the end of accessible memory, with a read
beyond its real end potentially resulting in some kind of memory
fault.
I filed a bug for the RelocationHolder constructors:
https://bugs.openjdk.java.net/browse/JDK-8160404
------------------------------------------------------------------------------
src/share/vm/code/relocInfo.hpp
495 void* _relocbuf[ _relocbuf_size ] = {0};
I'm not sure why this might be needed, but I don't think this is valid
C++98 code. I think this is actually using a C++14 feature.
I fixed as below.
It works fine.
----------
diff -r ba08710f3b6c src/share/vm/code/relocInfo.hpp
--- a/src/share/vm/code/relocInfo.hpp Mon Jun 27 09:35:18 2016 +0200
+++ b/src/share/vm/code/relocInfo.hpp Tue Jun 28 12:10:09 2016 +0900
@@ -850,7 +850,7 @@
// certain inlines must be deferred until class Relocation is defined:
-inline RelocationHolder::RelocationHolder() {
+inline RelocationHolder::RelocationHolder() : _relocbuf() {
// initialize the vtbl, just to keep things type-safe
new(*this) Relocation();
}
----------
Should I start to work for it after [1] ?
Or should I work for assembler_x86.cpp and relocInfo.hpp ?
Yasumasa
[1] http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-June/023696.html
