This is the first release to benefit from much broader continuous integration testing, thanks to @davidtgoldblatt. Had we had this testing infrastructure in place for prior releases, it would have caught all of the most serious regressions fixed by this release.

New features:

• Add --disable-thp and the opt.thp mallctl to provide opt-out mechanisms for transparent huge page integration. (@jasone)
• Update zone allocator integration to work with macOS 10.12. (@glandium)
• Restructure *CFLAGS configuration, so that CFLAGS behaves typically, and EXTRA_CFLAGS provides a way to specify e.g. -Werror during building, but not during configuration. (@jasone, @ronawho)

Bug fixes:

• Fix DSS (sbrk(2)-based) allocation. This regression was first released in 4.3.0. (@jasone)
• Handle race in per size class utilization computation. This functionality was first released in 4.0.0. (@interwq)
• Fix lock order reversal during gdump. (@jasone)
• Fix/refactor tcache synchronization. This regression was first released in 4.0.0. (@jasone)
• Fix various JSON-formatted malloc_stats_print() bugs. This functionality was first released in 4.3.0. (@jasone)
• Fix huge-aligned allocation. This regression was first released in 4.4.0. (@jasone)
• When transparent huge page integration is enabled, detect what state pages start in according to the kernel's current operating mode, and only convert arena chunks to non-huge during purging if that is not their initial state. This functionality was first released in 4.4.0. (@jasone)
• Fix lg_chunk clamping for the --enable-cache-oblivious --disable-fill case. This regression was first released in 4.0.0. (@jasone, @428desmo)
• Properly detect sparc64 when building for Linux. (@glaubitz)