Warnings Cleanup in Hotspot

[Calvin Cheung]

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/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
>