# Ann: SWI-Prolog 8.1.20 **URL:** https://swi-prolog.discourse.group/t/ann-swi-prolog-8-1-20/1699 **Category:** Releases **Created:** [January 4, 2020, 1:06pm UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-1-20/1699 "2020-01-04T13:06:21Z") **Posts on this page:** 1 **Page:** 1
### Author: ![jan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/jan/32/4_2.png) [@jan](https://swi-prolog.discourse.group/u/jan) #### Post date: [January 4, 2020, 1:06pm UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-1-20/1699/1 "2020-01-04T13:06:21Z")
Dear SWI-Prolog user, First of all, a good 2020! I’ve uploaded SWI-Prolog 8.1.20. This version does not bring not a lot of novel stuff, but it does address many important issues. Highlights: - Fixed a number of issues affecting Pengines and SWISH that boosts the stability of SWISH. - Avoid goal\_failed(http\_process/4) messages in the HTTP server. These were caused by the remote closing the connection before reading the entire document with a specific timing. - A number of patches deal with handling multiple interactive toplevel loops (in threads). This mostly concerns I/O and thread management from C. These support the new [libssh](https://www.swi-prolog.org/pack/list?p=libssh) pack that allows for secure login to a Prolog process, providing a full shell including command line editing, history, interrupt (^C), color support, and redirect of the output of shell commands. - Keri Harris found and fixed a possible asserting failure related to clause garbage collection. - There is a new library(intercept), resulting from the discussion on error handling on this forum. This is based on Ciao’s design. - The JPL .jar files now support Java 7 and up (used to depend on the Java version of the build machine, which varied between platforms). - pack\_install/1 and friends can now deal with CMake based add-ons, running cmake if there is a CMakeLists.txt file in the toplevel of the pack. See the libssh pack for an example. - Several contributed patches to the docs and tests by Boris Vassilev and C. M. Sperberg-McQueen. # SWI-Prolog Changelog since version 8.1.19 - BUILD: Use `-DJAVA_COMPATIBILITY=ON` for building Windows and MacOS binaries - FIXED: clause\_info/5 for `x==X`. @since d65c713cb2507a62b64d860a30246e05279bc522 - FIXED: clause\_info/5: avoid false binding if the arguments of =/2 are reversed. - ADDED: library(intercept): provide Ciao compatible intercept/signal API. - ADDED: prolog\_frame\_attribute/3: attribute `parent_goal(Next)` to allow enumeration of parent goals. Needed for the new library(intercept). - TEST: tests for library(dcg/high\_order) - DOC: Correct a few typos, supply leading zeroes in ISO 8601-style dates - FIXED: clause GC may mark indexes as dirty even though they do not include clauses being deleted - MODIFIED: The debug utility mutex\_statistics/0 now prints its output to `current_output` such that it can be redirected and ends up in the new SSH consoles. - ADDED: thread\_alias/1 to give a thread an alias name after creation. - FIXED: PL\_thread\_attach\_engine() if this call fails, do not leave the thread-local variable pointing at the destroyed local data. - FIXED: Handle ‘e’ in the debugger from a thread. Now safely terminates the thread using abort/0. - ENHANCED: Properly handle console mode management if we are communicating with multiple TTY devices. This is needed to support the new `libssh` package. - FIXED: on\_signal/3 not to fail if the signal is bound to a handler in a different module. - DOC: Updated and clarified documentation for on\_signal/3. - MODIFIED: on\_signal/2 now interprets `debug` as reserved handler name, triggering the default ^C handler. - ENHANCED: library(prolog\_colour): qualified tabling declarations and avoid type error warnings on partially instantiated predicate indicators in declarations. The latter is a bit dubious as it will indicate variables in e.g. `:- dynamic p/N` just as singleton. It does however avoid a screaming warning when using dynamic in runtime calls from a computed arity. - ENHANCED: CMake based packs to run `ctest` if the project defines tests. - ADDED: Support configuration and building of foreign packs using CMake. This is triggered if the pack root directory contains `CMakeLists.txt`. - MODIFIED: shell/1,2: if the `user_input`, `user_output` and `user_error` streams are connected to a file descriptors, `dup()` these to the process’ standard streams. This allows running shell commands and get the output in the expected place using the upcoming embedded SSH server. - FIXED: set\_prolog\_IO/3: make sure the file\_no(N) stream property is relayed properly. ## Package clib - FIXED: process\_create/3: `stderr` was sent to `stdout`. Reported by Jos Deroo. @since 9ea716e2c90fc359f03b1a838d9b764ca683608f - MODIFIED: process\_create/3: `std` I/O now uses the file handles underlying `user_input`, `user_output` and `user_error` rather than the hard coded 0,1,2. This allows using process\_create/3 with standard handles in secondary consoles. ## Package http - ENHANCED: Do not print errors to the console for sending files where the client aborts the connection before completion. - FIXED: Avoid goal\_failed(http\_process/4 messages, possible if sending the main message results in a broken pipe error. ## Package libedit - FIXED: el\_wrapped/1: avoid ignoring a possible exception. - FIXED: el\_unwrap/1: avoid ignoring a possible exception. ## Package pengines - FIXED: Avoid a race condition between a terminating Pengine and using its module for reading the next event arriving through HTTP. Access to the temporary module being destroyed is illegal.