Short-circuit commonly called witness functions so that they only
execute in debug builds, and remove equivalent guards from mutex
functions.  This avoids pointless code execution in
witness_assert_lockless(), which is typically called twice per
allocation/deallocation function invocation.

Inline commonly called witness functions so that optimized builds can
completely remove calls as dead code.

Fix in place huge reallocation to update the chunk counters that are
used for triggering gdump profiles.

b2c0d632 (Add witness, a simple online
locking validator.) caused a broad propagation of tsd throughout the
internal API, but tsd_fetch() was designed to fail prior to tsd
bootstrapping.  Fix this by splitting tsd_t into non-nullable tsd_t and
nullable tsdn_t, and modifying all internal APIs that do not critically
rely on tsd to take nullable pointers.  Furthermore, add the
tsd_booted_get() function so that tsdn_fetch() can probe whether tsd
bootstrapping is complete and return NULL if not.  All dangerous
conversions of nullable pointers are tsdn_tsd() calls that assert-fail
on invalid conversion.

This is a broader application of optimizations to malloc() and free() in
f4a0f32d (Fast-path improvement:
reduce # of branches and unnecessary operations.).

This resolves #321.

If the OS overcommits:
- Commit all mappings in pages_map() regardless of whether the caller
  requested committed memory.
- Linux-specific: Specify MAP_NORESERVE to avoid
  unfortunate interactions with heuristic overcommit mode during
  fork(2).

This resolves #193.

This makes the numbers reported in the leak report summary closely match
those reported by jeprof.

This resolves #356.

This resolves #367.

Link libjemalloc against librt if clock_gettime(2) is in librt rather
than libc, as for versions of glibc prior to 2.17.

This resolves #349.

Depending on virtual memory resource limits, it is necessary to attempt
allocating three maximally sized objects to trigger OOM rather than just
two, since the maximum supported size is slightly less than half the
total virtual memory address space.

This fixes a test failure that was introduced by
0c516a00 (Make *allocx() size class
overflow behavior defined.).

This resolves #379.

Split arena_choose() into arena_[i]choose() and use arena_ichoose() for
arena lookup during internal allocation.  This fixes huge_palloc() so
that it always succeeds during extent node allocation.

This regression was introduced by
66cd9535 (Do not allocate metadata via
non-auto arenas, nor tcaches.).

This assures that side effects of internal allocation don't impact
tests.

This regression was caused by 8f683b94
(Make opt_narenas unsigned rather than size_t.).

Fix bitmap_sfu() to shift by LG_BITMAP_GROUP_NBITS rather than
hard-coded 6 when using linear (non-USE_TREE) bitmap search.  In
practice this affects only 64-bit systems for which sizeof(long) is not
8 (i.e. Windows), since USE_TREE is defined for 32-bit systems.

This regression was caused by b8823ab0
(Use linear scan for small bitmaps).

This resolves #368.

Move chunk_dalloc_arena()'s implementation into chunk_dalloc_wrapper(),
so that if the dalloc hook fails, proper decommit/purge/retain cascading
occurs.  This fixes three potential chunk leaks on OOM paths, one during
dss-based chunk allocation, one during chunk header commit (currently
relevant only on Windows), and one during rtree write (e.g. if rtree
node allocation fails).

Merge chunk_purge_arena() into chunk_purge_default() (refactor, no
change to functionality).

Stack corruption happens in x64 bit

This resolves #347.

Depending on virtual memory resource limits, it is necessary to attempt
allocating three maximally sized objects to trigger OOM rather than just
two, since the maximum supported size is slightly less than half the
total virtual memory address space.

This fixes a test failure that was introduced by
0c516a00 (Make *allocx() size class
overflow behavior defined.).

This resolves #379.

Fix witness to clear its list of owned mutexes in the child if
platform-specific malloc_mutex code re-initializes mutexes rather than
unlocking them.