Update ChangeLog for 4.0.1.

ChangeLog

@@ -4,39 +4,62 @@ brevity.  Much more detail can be found in the git revision history:
 
     https://github.com/jemalloc/jemalloc
 
-* 4.0.1 (XXX)
+* 4.0.1 (September 15, 2015)
+
+  This is a bugfix release that is somewhat high risk due to the amount of
+  refactoring required to address deep xallocx() problems.  As a side effect of
+  these fixes, xallocx() now tries harder to partially fulfill requests for
+  optional extra space.  Note that a couple of minor heap profiling
+  optimizations are included, but these are better thought of as performance
+  fixes that were integral to disovering most of the other bugs.
+
+  Optimizations:
+  - Avoid a chunk metadata read in arena_prof_tctx_set(), since it is in the
+    fast path when heap profiling is enabled.  Additionally, split a special
+    case out into arena_prof_tctx_reset(), which also avoids chunk metadata
+    reads.
+  - Optimize irallocx_prof() to optimistically update the sampler state.  The
+    prior implementation appears to have been a holdover from when
+    rallocx()/xallocx() functionality was combined as rallocm().
 
   Bug fixes:
+  - Fix TLS configuration such that it is enabled by default for platforms on
+    which it works correctly.
   - Fix arenas_cache_cleanup() and arena_get_hard() to handle
     allocation/deallocation within the application's thread-specific data
     cleanup functions even after arenas_cache is torn down.
-  - Don't bitshift by negative amounts when encoding/decoding run sizes in chunk
-    header maps.  This affected systems with page sizes greater than 8 KiB.
-  - Rename index_t to szind_t to avoid an existing type on Solaris.
-  - Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to
-    match glibc and avoid compilation errors when including both
-    jemalloc/jemalloc.h and malloc.h in C++ code.
+  - Fix xallocx() bugs related to size+extra exceeding HUGE_MAXCLASS.
   - Fix chunk purge hook calls for in-place huge shrinking reallocation to
     specify the old chunk size rather than the new chunk size.  This bug caused
     no correctness issues for the default chunk purge function, but was
     visible to custom functions set via the "arena.<i>.chunk_hooks" mallctl.
-  - Fix TLS configuration such that it is enabled by default for platforms on
-    which it works correctly.
-  - Fix heap profiling to distinguish among otherwise identical sample sites
+  - Fix heap profiling bugs:
+    + Fix heap profiling to distinguish among otherwise identical sample sites
       with interposed resets (triggered via the "prof.reset" mallctl).  This bug
       could cause data structure corruption that would most likely result in a
       segfault.
-  - Fix xallocx() bugs related to size+extra exceeding HUGE_MAXCLASS.
-  - Fix irealloc_prof() to prof_alloc_rollback() on OOM.
-  - Make one call to prof_active_get_unlocked() per allocation event, and use
+    + Fix irealloc_prof() to prof_alloc_rollback() on OOM.
+    + Make one call to prof_active_get_unlocked() per allocation event, and use
       the result throughout the relevant functions that handle an allocation
       event.  Also add a missing check in prof_realloc().  These fixes protect
       allocation events against concurrent prof_active changes.
-  - Fix ixallocx_prof() to pass usize_max and zero to ixallocx_prof_sample() in
-    the correct order.
-  - Fix prof_realloc() to call prof_free_sampled_object() after calling
+    + Fix ixallocx_prof() to pass usize_max and zero to ixallocx_prof_sample()
+      in the correct order.
+    + Fix prof_realloc() to call prof_free_sampled_object() after calling
       prof_malloc_sample_object().  Prior to this fix, if tctx and old_tctx were
       the same, the tctx could have been prematurely destroyed.
+  - Fix portability bugs:
+    + Don't bitshift by negative amounts when encoding/decoding run sizes in
+      chunk header maps.  This affected systems with page sizes greater than 8
+      KiB.
+    + Rename index_t to szind_t to avoid an existing type on Solaris.
+    + Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to
+      match glibc and avoid compilation errors when including both
+      jemalloc/jemalloc.h and malloc.h in C++ code.
+    + Don't assume that /bin/sh is appropriate when running size_classes.sh
+      during configuration.
+    + Consider __sparcv9 a synonym for __sparc64__ when defining LG_QUANTUM.
+    + Link tests to librt if it contains clock_gettime(2).
 
 * 4.0.0 (August 17, 2015)