Warnings Cleanup in Hotspot
David Holmes
david.holmes at oracle.com
Thu May 16 18:59:56 PDT 2013
Calvin,
On 17/05/2013 4:55 AM, Calvin Cheung wrote:
> Jeremy,
>
> It seems your suggested patch is incomplete as the build on linux was
> failing.
> Recall that warnings are treated as errors as in gcc.make:
> # Compiler warnings are treated as errors
> WARNINGS_ARE_ERRORS = -Werror
>
> Below is the list of files I needed to change for the build to go
> through on linux:
> make/linux/makefiles/gcc.make
> src/share/vm/c1/c1_IR.cpp
> src/share/vm/ci/ciUtilities.hpp
> src/share/vm/classfile/genericSignatures.cpp
> src/share/vm/classfile/verifier.hpp
> src/share/vm/code/nmethod.cpp
> src/share/vm/memory/cardTableModRefBS.cpp
> src/share/vm/memory/universe.cpp
> src/share/vm/oops/constantPool.cpp
> src/share/vm/prims/forte.cpp
> src/share/vm/runtime/perfData.hpp
> src/share/vm/runtime/sharedRuntime.cpp
> src/share/vm/services/diagnosticArgument.cpp
> src/share/vm/utilities/exceptions.hpp
> src/share/vm/utilities/taskqueue.hpp
>
> Most of the warnings are related to: "statement has no effect"
> e.g. in exceptions.hpp, I needed to change
> #define CHECK THREAD); if
> (HAS_PENDING_EXCEPTION) return ; (0
> to
> #define CHECK THREAD); if
> (HAS_PENDING_EXCEPTION) return ; (void)(0
>
> I don't want to share webrev yet since I haven't built on other
> platforms and haven't done any testing on the change.
>
> 2 ways I'm thinking of fixing it:
> 1) include the -Wunused-value warning flag
> this means changes are required on the files listed above
>
> 2) not include the -Wunused-value warning flag but only fixing the
> potential coding errors which would impact functionality as you pointed
> out in your email. This should result in a smaller changeset.
I think I prefer #2 mainly because:
0;
and
(void)0;
are equally bereft of any effect so I don't see why the compiler
complains about one and accepts the other. As this seems completely
arbitrary different compilers may have different views, or change their
view over time. So I suggest not changing this and only fix the real
issues that -Wunused-value produces.
Just my 2c.
David
------
> Calvin
>
> On 5/16/2013 10:55 AM, Jeremy Manson wrote:
>> Okay. Is there anything you want me to do?
>>
>> Jeremy
>>
>>
>> On Wed, May 15, 2013 at 2:37 PM, Calvin Cheung
>> <calvin.cheung at oracle.com <mailto:calvin.cheung at oracle.com>> wrote:
>>
>> Jeremy,
>>
>> We'll fix it in hs25 first and then backport it to hs24 if the fix
>> is applicable there.
>>
>> Calvin
>>
>>
>> On 5/15/2013 2:14 PM, Jeremy Manson wrote:
>>> Thanks, Calvin. What does followup look like?
>>>
>>> Jeremy
>>>
>>>
>>> On Mon, May 13, 2013 at 9:59 AM, Calvin Cheung
>>> <calvin.cheung at oracle.com <mailto:calvin.cheung at oracle.com>> wrote:
>>>
>>> Hi Jeremy,
>>>
>>> I've created 8014431 (cleanup warnings indicated by the
>>> -Wunused-value compiler option on linux) to track this. It'll
>>> take a few hours for it to show up in the bugs.sun.com
>>> <http://bugs.sun.com>
>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8014431
>>>
>>> Calvin
>>>
>>>
>>> On 5/10/2013 11:38 AM, Jeremy Manson wrote:
>>>
>>> Okay, I turned on -Wunused-value in the gcc makefile for
>>> Linux. I also ran this on a more recent build of HS (I
>>> was using something very, very old), and I got a few more
>>> warnings (including a couple that actually looked as if
>>> they would impact functionality). Thoughts on this?
>>>
>>> diff --git a/make/linux/makefiles/gcc.make
>>> b/make/linux/makefiles/gcc.make
>>> --- a/make/linux/makefiles/gcc.make
>>> +++ b/make/linux/makefiles/gcc.make
>>> @@ -126,7 +126,7 @@
>>> # Compiler warnings are treated as errors
>>> WARNINGS_ARE_ERRORS = -Werror
>>> -WARNING_FLAGS = -Wpointer-arith -Wsign-compare -Wundef
>>> -Wunused-function
>>> +WARNING_FLAGS = -Wpointer-arith -Wsign-compare -Wundef
>>> -Wunused-function -Wunused-value
>>> # Since GCC 4.3, -Wconversion has changed its meanings
>>> to warn these implicit
>>> # conversions which might affect the values. Only enable
>>> it in earlier versions.
>>> diff --git a/src/share/vm/c1/c1_IR.cpp
>>> b/src/share/vm/c1/c1_IR.cpp
>>> --- a/src/share/vm/c1/c1_IR.cpp
>>> +++ b/src/share/vm/c1/c1_IR.cpp
>>> @@ -506,7 +506,7 @@
>>> _loop_map(0, 0), // initialized later with
>>> correct size
>>> _compilation(c)
>>> {
>>> - TRACE_LINEAR_SCAN(2, "***** computing linear-scan
>>> block order");
>>> + TRACE_LINEAR_SCAN(2, tty->print_cr("***** computing
>>> linear-scan block order"));
>>> init_visited();
>>> count_edges(start_block, NULL);
>>> @@ -683,7 +683,7 @@
>>> }
>>> void
>>> ComputeLinearScanOrder::assign_loop_depth(BlockBegin*
>>> start_block) {
>>> - TRACE_LINEAR_SCAN(3, "----- computing loop-depth and
>>> weight");
>>> + TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing
>>> loop-depth and weight"));
>>> init_visited();
>>> assert(_work_list.is_empty(), "work list must be empty
>>> before processing");
>>> @@ -868,7 +868,7 @@
>>> }
>>> void ComputeLinearScanOrder::compute_order(BlockBegin*
>>> start_block) {
>>> - TRACE_LINEAR_SCAN(3, "----- computing final block order");
>>> + TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing
>>> final block order"));
>>> // the start block is always the first block in the
>>> linear scan order
>>> _linear_scan_order = new BlockList(_num_blocks);
>>> diff --git a/src/share/vm/code/nmethod.cpp
>>> b/src/share/vm/code/nmethod.cpp
>>> --- a/src/share/vm/code/nmethod.cpp
>>> +++ b/src/share/vm/code/nmethod.cpp
>>> @@ -2602,7 +2602,8 @@
>>> relocation_begin()-1+ip[1]);
>>> for (; ip < index_end; ip++)
>>> tty->print_cr(" (%d ?)", ip[0]);
>>> - tty->print_cr(" @" INTPTR_FORMAT ":
>>> index_size=%d", ip, *ip++);
>>> + tty->print_cr(" @" INTPTR_FORMAT ":
>>> index_size=%d", ip, *ip);
>>> + ip++;
>>> tty->print_cr("reloc_end @" INTPTR_FORMAT ":", ip);
>>> }
>>> }
>>> diff --git a/src/share/vm/memory/cardTableModRefBS.cpp
>>> b/src/share/vm/memory/cardTableModRefBS.cpp
>>> --- a/src/share/vm/memory/cardTableModRefBS.cpp
>>> +++ b/src/share/vm/memory/cardTableModRefBS.cpp
>>> @@ -395,7 +395,7 @@
>>> }
>>> // Touch the last card of the covered region to show
>>> that it
>>> // is committed (or SEGV).
>>> - debug_only(*byte_for(_covered[ind].last());)
>>> + debug_only((void) (*byte_for(_covered[ind].last()));)
>>> debug_only(verify_guard();)
>>> }
>>> diff --git a/src/share/vm/memory/universe.cpp
>>> b/src/share/vm/memory/universe.cpp
>>> --- a/src/share/vm/memory/universe.cpp
>>> +++ b/src/share/vm/memory/universe.cpp
>>> @@ -532,7 +532,9 @@
>>> if (vt) vt->initialize_vtable(false, CHECK);
>>> if (ko->oop_is_instance()) {
>>> InstanceKlass* ik = (InstanceKlass*)ko;
>>> - for (KlassHandle s_h(THREAD, ik->subklass()); s_h()
>>> != NULL; s_h = (THREAD, s_h()->next_sibling())) {
>>> + for (KlassHandle s_h(THREAD, ik->subklass());
>>> + s_h() != NULL;
>>> + s_h = KlassHandle(THREAD, s_h()->next_sibling())) {
>>> reinitialize_vtable_of(s_h, CHECK);
>>> }
>>> }
>>> diff --git a/src/share/vm/runtime/sharedRuntime.cpp
>>> b/src/share/vm/runtime/sharedRuntime.cpp
>>> --- a/src/share/vm/runtime/sharedRuntime.cpp
>>> +++ b/src/share/vm/runtime/sharedRuntime.cpp
>>> @@ -2733,7 +2733,7 @@
>>> // ResourceObject, so do not put any ResourceMarks in
>>> here.
>>> char *s = sig->as_C_string();
>>> int len = (int)strlen(s);
>>> - *s++; len--; // Skip opening paren
>>> + s++; len--; // Skip opening paren
>>> char *t = s+len;
>>> while( *(--t) != ')' ) ; // Find close paren
>>> diff --git a/src/share/vm/services/diagnosticArgument.cpp
>>> b/src/share/vm/services/diagnosticArgument.cpp
>>> --- a/src/share/vm/services/diagnosticArgument.cpp
>>> +++ b/src/share/vm/services/diagnosticArgument.cpp
>>> @@ -232,7 +232,7 @@
>>> } else {
>>> _value._time = 0;
>>> _value._nanotime = 0;
>>> - strcmp(_value._unit, "ns");
>>> + strcpy(_value._unit, "ns");
>>> }
>>> }
>>> diff --git a/src/share/vm/utilities/taskqueue.hpp
>>> b/src/share/vm/utilities/taskqueue.hpp
>>> --- a/src/share/vm/utilities/taskqueue.hpp
>>> +++ b/src/share/vm/utilities/taskqueue.hpp
>>> @@ -340,8 +340,12 @@
>>> if (dirty_n_elems == N - 1) {
>>> // Actually means 0, so do the push.
>>> uint localBot = _bottom;
>>> - // g++ complains if the volatile result of the
>>> assignment is unused.
>>> - const_cast<E&>(_elems[localBot] = t);
>>> + // g++ complains if the volatile result of the
>>> assignment is
>>> + // unused, so we cast the volatile away. We cannot
>>> cast directly
>>> + // to void, because gcc treats that as not using the
>>> result of the
>>> + // assignment. However, casting to E& means that we
>>> trigger an
>>> + // unused-value warning. So, we cast the E& to void.
>>> + (void) const_cast<E&>(_elems[localBot] = t);
>>> OrderAccess::release_store(&_bottom,
>>> increment_index(localBot));
>>> TASKQUEUE_STATS_ONLY(stats.record_push());
>>> return true;
>>> @@ -397,7 +401,12 @@
>>> return false;
>>> }
>>> - const_cast<E&>(t = _elems[oldAge.top()]);
>>> + // g++ complains if the volatile result of the
>>> assignment is
>>> + // unused, so we cast the volatile away. We cannot
>>> cast directly
>>> + // to void, because gcc treats that as not using the
>>> result of the
>>> + // assignment. However, casting to E& means that we
>>> trigger an
>>> + // unused-value warning. So, we cast the E& to void.
>>> + (void) const_cast<E&>(t = _elems[oldAge.top()]);
>>> Age newAge(oldAge);
>>> newAge.increment();
>>> Age resAge = _age.cmpxchg(newAge, oldAge);
>>> @@ -640,8 +649,12 @@
>>> uint dirty_n_elems = dirty_size(localBot, top);
>>> assert(dirty_n_elems < N, "n_elems out of range.");
>>> if (dirty_n_elems < max_elems()) {
>>> - // g++ complains if the volatile result of the
>>> assignment is unused.
>>> - const_cast<E&>(_elems[localBot] = t);
>>> + // g++ complains if the volatile result of the
>>> assignment is
>>> + // unused, so we cast the volatile away. We cannot
>>> cast directly
>>> + // to void, because gcc treats that as not using the
>>> result of the
>>> + // assignment. However, casting to E& means that we
>>> trigger an
>>> + // unused-value warning. So, we cast the E& to void.
>>> + (void) const_cast<E&>(_elems[localBot] = t);
>>> OrderAccess::release_store(&_bottom,
>>> increment_index(localBot));
>>> TASKQUEUE_STATS_ONLY(stats.record_push());
>>> return true;
>>> @@ -665,7 +678,12 @@
>>> // This is necessary to prevent any read below from
>>> being reordered
>>> // before the store just above.
>>> OrderAccess::fence();
>>> - const_cast<E&>(t = _elems[localBot]);
>>> + // g++ complains if the volatile result of the
>>> assignment is
>>> + // unused, so we cast the volatile away. We cannot
>>> cast directly
>>> + // to void, because gcc treats that as not using the
>>> result of the
>>> + // assignment. However, casting to E& means that we
>>> trigger an
>>> + // unused-value warning. So, we cast the E& to void.
>>> + (void) const_cast<E&>(t = _elems[localBot]);
>>> // This is a second read of "age"; the "size()" above
>>> is the first.
>>> // If there's still at least one element in the queue,
>>> based on the
>>> // "_bottom" and "age" we've read, then there can be
>>> no interference with
>>>
>>>
>>>
>>
>>
>
More information about the hotspot-runtime-dev
mailing list