Log Message:
Updated jemalloc to 4.2.1.

Provided by Jonathan Buschmann in PR 51302.

* 4.2.1 (June 8, 2016)

  Bug fixes:
  - Fix bootstrapping issues for configurations that require allocation during
    tsd initialization (e.g. --disable-tls).  (@cferris1000, @jasone)
  - Fix gettimeofday() version of nstime_update().  (@ronawho)
  - Fix Valgrind regressions in calloc() and chunk_alloc_wrapper().  (@ronawho)
  - Fix potential VM map fragmentation regression.  (@jasone)
  - Fix opt_zero-triggered in-place huge reallocation zeroing.  (@jasone)
  - Fix heap profiling context leaks in reallocation edge cases.  (@jasone)

* 4.2.0 (May 12, 2016)

  New features:
  - Add the arena.<i>.reset mallctl, which makes it possible to discard all of
    an arena's allocations in a single operation.  (@jasone)
  - Add the stats.retained and stats.arenas.<i>.retained statistics.  (@jasone)
  - Add the --with-version configure option.  (@jasone)
  - Support --with-lg-page values larger than actual page size.  (@jasone)

  Optimizations:
  - Use pairing heaps rather than red-black trees for various hot data
    structures.  (@djwatson, @jasone)
  - Streamline fast paths of rtree operations.  (@jasone)
  - Optimize the fast paths of calloc() and [m,d,sd]allocx().  (@jasone)
  - Decommit unused virtual memory if the OS does not overcommit.  (@jasone)
  - Specify MAP_NORESERVE on Linux if [heuristic] overcommit is active, in order
    to avoid unfortunate interactions during fork(2).  (@jasone)

  Bug fixes:
  - Fix chunk accounting related to triggering gdump profiles.  (@jasone)
  - Link against librt for clock_gettime(2) if glibc < 2.17.  (@jasone)
  - Scale leak report summary according to sampling probability.  (@jasone)

* 4.1.1 (May 3, 2016)

  This bugfix release resolves a variety of mostly minor issues, though the
  bitmap fix is critical for 64-bit Windows.

  Bug fixes:
  - Fix the linear scan version of bitmap_sfu() to shift by the proper amount
    even when sizeof(long) is not the same as sizeof(void *), as on 64-bit
    Windows.  (@jasone)
  - Fix hashing functions to avoid unaligned memory accesses (and resulting
    crashes).  This is relevant at least to some ARM-based platforms.
    (@rkmisra)
  - Fix fork()-related lock rank ordering reversals.  These reversals were
    unlikely to cause deadlocks in practice except when heap profiling was
    enabled and active.  (@jasone)
  - Fix various chunk leaks in OOM code paths.  (@jasone)
  - Fix malloc_stats_print() to print opt.narenas correctly.  (@jasone)
  - Fix MSVC-specific build/test issues.  (@rustyx, @yuslepukhin)
  - Fix a variety of test failures that were due to test fragility rather than
    core bugs.  (@jasone)

* 4.1.0 (February 28, 2016)

  This release is primarily about optimizations, but it also incorporates a lot
  of portability-motivated refactoring and enhancements.  Many people worked on
  this release, to an extent that even with the omission here of minor changes
  (see git revision history), and of the people who reported and diagnosed
  issues, so much of the work was contributed that starting with this release,
  changes are annotated with author credits to help reflect the collaborative
  effort involved.

  New features:
  - Implement decay-based unused dirty page purging, a major optimization with
    mallctl API impact.  This is an alternative to the existing ratio-based
    unused dirty page purging, and is intended to eventually become the sole
    purging mechanism.  New mallctls:
    + opt.purge
    + opt.decay_time
    + arena.<i>.decay
    + arena.<i>.decay_time
    + arenas.decay_time
    + stats.arenas.<i>.decay_time
    (@jasone, @cevans87)
  - Add --with-malloc-conf, which makes it possible to embed a default
    options string during configuration.  This was motivated by the desire to
    specify --with-malloc-conf=purge:decay , since the default must remain
    purge:ratio until the 5.0.0 release.  (@jasone)
  - Add MS Visual Studio 2015 support.  (@rustyx, @yuslepukhin)
  - Make *allocx() size class overflow behavior defined.  The maximum
    size class is now less than PTRDIFF_MAX to protect applications against
    numerical overflow, and all allocation functions are guaranteed to indicate
    errors rather than potentially crashing if the request size exceeds the
    maximum size class.  (@jasone)
  - jeprof:
    + Add raw heap profile support.  (@jasone)
    + Add --retain and --exclude for backtrace symbol filtering.  (@jasone)

  Optimizations:
  - Optimize the fast path to combine various bootstrapping and configuration
    checks and execute more streamlined code in the common case.  (@interwq)
  - Use linear scan for small bitmaps (used for small object tracking).  In
    addition to speeding up bitmap operations on 64-bit systems, this reduces
    allocator metadata overhead by approximately 0.2%.  (@djwatson)
  - Separate arena_avail trees, which substantially speeds up run tree
    operations.  (@djwatson)
  - Use memoization (boot-time-computed table) for run quantization.  Separate
    arena_avail trees reduced the importance of this optimization.  (@jasone)
  - Attempt mmap-based in-place huge reallocation.  This can dramatically speed
    up incremental huge reallocation.  (@jasone)

  Incompatible changes:
  - Make opt.narenas unsigned rather than size_t.  (@jasone)

  Bug fixes:
  - Fix stats.cactive accounting regression.  (@rustyx, @jasone)
  - Handle unaligned keys in hash().  This caused problems for some ARM systems.
    (@jasone, @cferris1000)
  - Refactor arenas array.  In addition to fixing a fork-related deadlock, this
    makes arena lookups faster and simpler.  (@jasone)
  - Move retained memory allocation out of the default chunk allocation
    function, to a location that gets executed even if the application installs
    a custom chunk allocation function.  This resolves a virtual memory leak.
    (@buchgr)
  - Fix a potential tsd cleanup leak.  (@cferris1000, @jasone)
  - Fix run quantization.  In practice this bug had no impact unless
    applications requested memory with alignment exceeding one page.
    (@jasone, @djwatson)
  - Fix LinuxThreads-specific bootstrapping deadlock.  (Cosmin Paraschiv)
  - jeprof:
    + Don't discard curl options if timeout is not defined.  (@djwatson)
    + Detect failed profile fetches.  (@djwatson)
  - Fix stats.arenas.<i>.{dss,lg_dirty_mult,decay_time,pactive,pdirty} for
    --disable-stats case.  (@jasone)