Ann: SWI-Prolog 8.1.27

[jan]

Dear SWI-Prolog user,

SWI-Prolog 8.1.27 is ready for download. This is mostly a bug fixing,
portability and build/installation release. Highlights:

• Allow (and by default do) linking to Google tcmalloc as an
  alternative to the system malloc() routines. Tcmalloc seems to
  provide much better memory reuse, notably on programs that create
  many threads and a lot of garbage atoms and clauses. It works
  poorly for stack allocation and temporary allocation of large
  chunks. These are now handled using mmap() directly. Currently
  Unix only.

• There is a new predicate thread_idle/2 that can be wrapped
  around a goal that will make the calling thread idle for some
  time, e.g., waiting for a new message or activity on a stream.
  This predicate releases resources to the system before waiting.

• A lot of new statistics and size properties have been added
  to various object types to get better insight in memory use.

• With help from Lev Lamberov and Keri Haris atomic data management
  has been switched to the newer GCC __atomic* built-ins. This
  notably facilitates 32-bit platforms that lack 64 bit atomic
  instructions (e.g. 32-bit MIPS)

• Matt Lilley fixed OpenSSL issues: failing test using OpenSSL
  1.1.1e (timeout handling) and too short test certificates
  causing most tests to fail on Debian 10.3 (Buster) and probably
  many other systems.

• Several new build and test options.

  Enjoy — Jan

SWI-Prolog Changelog since version 8.1.26

• FIXED: Possible wrong NaN from the nexttoward/1 function.

• PORT: 1.0**NaN is not always 1.0 in all C versions.

• MODIFIED: float_fractional_part/1 and float_integer_part/1 functions
  to return standard NaN (fix) or raise an exception if float_undefined
  is set to error.

• INSTALL: When installing tests, add them to the optional component
  “Tests”

• TEST: Fixed test thread/thr_local_1.pl.

• FIXED: Ensure we have a universal NaN that is 1.5NaN. This test
  failed on mipsel.

• TEST: Fixed test_clause_gc.pl test as this can run out of stack since
  we combine the stacks.

• TEST: Provide test_tmp_dir search path when running installed tests
  such that they can run without writing in the test directory.

• TEST: remove protocol(x) from thread_agc test.

• DOC: Provide pldoc_to_tex flag when generating LaTeX, so code can
  decide to avoid loading dependencies that may not be present.

• PORT: Replace GCC _sync* functions by more recent _atomic*
  primitives to improve portability.

• DOC: PL_initialise() referred to old libpl.dll. Gerhard Groehner.

• ENHANCED: Use temporary allocation for buffers and discard large
  buffers when making them empty.

• ENHANCED: Use new tmp_malloc() for segstacks (used as temporary store
  for many operations that iterate over complex terms).

• CLEANUP: No longer allocate array for built-in atoms. This array is
  no longer used (saves 85Kbytes memory).

• INSTALL: Added CMake option SWIPL_INSTALL_IN_SHARE=ON to install
  architecture indepedent files in <prefix>/share/swipl/. Currently
  only used for the documentation and examples. Future versions may
  also place the library here. Lev Lamberov, Debian maintainer.

• ADDED: statistics/2 threads_peak to get an indication of the highest
  level of concurrency reached.

• CLEANUP: Move notion of highest thread id to global data structure.

• ADDED: thread_property/2: size(Bytes) property

• ADDED: statistics/2: atom_space and functor_space to get the used
  memory.

• ADDED: module_property/2: size(-Bytes)

• ADDED: predicate_property/2: size(-Bytes)

• FIXED: Added meta-predicate declaration for thread_idle/2.

• FIXED: Stack alloc statistics

• ENHANCED: Use new mmap() based allocation more generally for large
  temporary allocations. Currently used by findall/3 and friends.
  There are more candidates where this can help, such as buffers and
  stacks for cycle detection, enumerating large terms, etc.

• BUILD: Install the manual index as part of the documentation
  installation. Lev Lamberov.

• ENHANCED: Use mmap() based allocation for the stacks such that we
  can release these to the OS if we use an allocator that is not well
  suited for huge temporary stack allocations.

• ADDED: trie_property/2, statistics properties to access the IDG size.

• ADDED: check_installation/0: check for tcmalloc.

• PORT: Make tcmalloc setup work on MacOS. Signalled by Paulo Moura.

• PORT: Use our internal PL_dlsym() and work without tcmalloc

• ADDED: thread_idle/2 and, when linked to tcmalloc, malloc_property/1
  and set_malloc/1.

• ADDED: Detect tcmalloc() and link swipl using this if provided.

• PORT: Added CMake script to find tcmalloc

Package archive

• BUILD: Doc build depends on package itself.

Package bdb

• TEST: use test_tmp_dir to find a writeable place for the test output.

• FIXED: If a database cannot be opened it is still around as a current
  database and closing it (explicitly or at the end of the process)
  crashes.

Package clib

• PORT: Another use of extern environ that blocks MacOS 10.6.

Package http

• DOC: Avoid building docs to load SSL

• ENHANCED: Use new thread_idle/2 to wait for a new HTTP message.

• ENHANCED: library(http/http_unix_daemon): use thread_idle/2 while
  waiting for a maintenance event to reduce resource usage.

Package pcre

• DOC: Clarify re_matchsub/4.

Package semweb

• TEST: Avoid creating g1.rec for a normal test run.

• PORT: Use GCC __atomic instructions.

Package ssl

• TEST: Recreate the test certificates with 2048 bit keys since later
  versions of Debian (at least) will no longer accept 1024-bit keys

• FIXED: Timeout handling with OpenSSL 1.1.1e and later. Resolved by
  Matt Lilley.

• TEST: Document failing server test when using OpenSSL 1.1.1e

• FIXED: ssl_context/3: declare new cacerts option

• ENHANCED: avoid blocking if the SSL server tests fails.

• TEST: Cleanup test module (unneeded path handling, redundant newlines
  in debug/3 messages).

Package zlib

• TEST: Search for a writable directory for test_tmp_dirthe test files
  based on the (new) test_tmp_dir path alias.