# Ann: SWI-Prolog 8.5.16

**URL:** <https://swi-prolog.discourse.group/t/ann-swi-prolog-8-5-16/5749>\
**Category:** Releases\
**Created:** [September 7, 2022, 11:25am UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-5-16/5749 "2022-09-07T11:25:22Z")\
**Posts on this page:** 3\
**Page:** 1

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**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:** [September 7, 2022, 11:25am UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-5-16/5749/1 "2022-09-07T11:25:22Z")

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Dear SWI-Prolog user,

SWI-Prolog 8.5.16 is ready for download. It has been a long time, in  
part due to holidays and in part due to the many changes that made it  
hard to pick a good time for the release. Still, some work I rather had  
seen in 8.5.16 is not there yet. Notably I would have liked to see the  
work by @peter.ludemann on a new, more robust C++ interface that also  
covers a large part of the C API in 8.5.16. Unfortunately that needed to  
be posponed as we first need to fix some portability issues. Also the  
WASM version is not there where I had wished it would be. The Prolog  
WASM core is now fairly stable, but the JavaScript wrappers are not.  
Both the interface will change and the interface needs better error  
handling and testing. This is now targetted for 8.5.17.

Most work is on portability. Highlights:

- **Windows** version: various UTF-16 encoding issues, resolved many  
file system interaction issues: long paths, UTF-16 names, issues  
with Windows the C runtime library resolved by using the Win32  
API directly for a larger part of the code.
- **WASM** version: Core works fine. The meaningfull extensions are  
now included into the build. The applicable part of the test  
suite passes. JavaScript interface is still work in progress.
- Lots of changes to the package dependencies and configuration  
to improve support on restricted builds (notably single threaded).
- Fixes to engine and foreign _yield_.
- Several issues raised by the **Debian** maintainer (Lev). Hope  
to get 8.6.x into the next Debian release cycle.
- Fixed possible crash in crypto libraries by @maren

Due to the scope of the changes some regression is not unlikely. Please  
test and report.

```
Enjoy --- Jan

```

P.s. MacOS binaries will be available later today or tomorrow.  
Build machine is being updated …

# SWI-Prolog Changelog since version 8.5.15

- DOC: Fix typos, clarify return codes and error conditions for many  
foreign language interface functions (PL\_\*()).

- FIXED: If creating an atom fails due to invalid representation of the  
source text (e.g., invalid UTF-8 sequence) we now raise an exception.

- WASM: Using node we by default have no control over the terminal.  
Need to find out whether it is possible to make that work.

- TEST: Lower test recursion on systems with limited C stack

- WASM: Disabled IEEE754 tests as float rounding does not appear to be  
suported and many WASM float functions are imprecise.

- WASM: Do not support open(pipe(Command), …) as popen() is a dummy.

- FIXED: transaction/1 in single threaded version.

- ENHANCED: Simplify clause visibility rules with transactions.

- PORT: Windows: install a copy of libstdc++\*.dll while building and  
add this to the installer if INSTALL\_TESTS is active.

- PORT: Be more conservative with C stacks on WASM. Fixes dealing with  
cyclic terms in assert/1 and friends.

- BUILD: make\_library\_index/1 to silently ignore errors from  
use\_foreign\_library/1. This works around a dependency issue for  
building the INDEX.pl files during build. This is not ideal as in  
theory we could do exports conditionally based on what is in the  
foreign object. At this moment this does not happen.

- MODIFIED: qsave\_program/2 and compilation using `-c` to interpret the  
`--emulator=file`` flag (or emulator(Emulator) option) independently from the `–stand-alone`` option. This allows creating non-stand-alone  
executables that use a specific emulator path.

- TEST: When using `-DINSTALL_TESTS`, install foreign plugins that  
only support testing.

- DOC: Describe the design of the Windows file system interaction and  
its limitations.

- ENHANCED: Test Windows file identify using the device identifier to  
deal with links.

- TEST: Added more file name tests.

- FIXED: Windows: turned ‘$mark\_executable’/1 into a dummy as it does  
nothing meaningful anyway.

- FIXED: Windows opendir(), etc. emulation. Use more efficient file  
finding and avoid a possible inifinite loop.

- ENHANCED: expand\_file\_name/2: provide signal handling while expanding  
such that we can interrupt.

- FIXED: Windows working directory to use SetCurrentDirectoryW() for  
supporting longer path names.

- FIXED: Sprintf() for wide character strings with surrogate pairs.

- FIXED: Sprintf() for NULL char \* that have non-ASCII encoding.

- FIXED: Windows implementation of size\_file/2 to use  
GetFileAttributesExW() because \_wstati64() cannot handle long file  
names.

- ENHANCED: Windows: Use more robust translation to Windows path  
names. Support long file names using the `"\\?\"` or `"\\?UNC\"`  
prefix.

- FIXED: Windows dlopen() emulation path handling.

- ENHANCED: fallback to the default mem functions in the GMP hooks…  
…when invoked out of the context of Prolog.

- FIXED: Windows conversion to UTF-16 file names to introduce surrogate  
pairs when needed.

- MODIFIED: expand\_file\_name/2 return entries in simple lexical order  
rather than using mbscoll(). The latter did not work anyway because  
the pattern and file names use UTF-8 rather than native multibyte.

- FIXED: existence checking on Windows for expand\_file\_name/2

- FIXED: Windows: do not canonicalize characters of file names \> 0xffff  
using towlower() as this function truncates to 16 bits. Assumes there  
are no letters with case above 0xffff.

- FIXED: Windows: translation of `wchar_t` to UTF-8 for surrogate  
pairs. Fixes e.g. `?- string_bytes('\U0001f600\U0001f604', L, utf8).`

- FIXED: Windows: ensure surrogate pairs to the console streams are in  
the same WriteConsoleW() call. This fixes writing Unicode code points \>  
0xffff to `user_error`. The patch also writes output to `user_error`  
in larger chunks. Note that the default Windows console does not handle  
surrogate pairs. The Windows Terminal does.

- DOC: Describe poor exceptions from failing file system operations.

- FIXED: Actually use overruled PATH\_MAX in uxnt.c emulation.

- DOC: rename\_file/2: updated docs.

- ADDED: Prolog flag `path_max` to get access to the manimum file name  
length on the OS.

- FIXED: string\_bytes/2 in mode (+,-) for UTF-16 encoding on  
Windows. Reported by Matthias Gondan.

- PORT: Emscripten updates: Move required settings to Emscripten.cmake  
and add support for GMP

- DOC: Make compile if library(shlib) is not present

- FIXED: Issue#1025: stream encoding wchar\_t not returned as stream  
property

- FIXED: Issue#1021: engine\_next/2 for a next answer when the previous  
return was due to a yield crashes.

- FIXED: WASM Issue#1023: sleep/1 no longer worked.

- BUILD: Dependency issue for building the library indexes. After  
comments and a hint by Matthias Gondan.

- TEST: Avoid more tests that depend on threads in single threaded  
version.

- WASM: library(readutil): use shared use\_foreign\_library/1.

- WASM: Include http into wasm version

- WASM: Activate STATIC\_EXTENSIONS and include (part of) the clib  
package.

- BUILD: Build option `cmake -DSTATIC_EXTENSIONS` which adds selected  
extensions (packages) to libswipl. In this scenario dynamic linking  
is disabled and use\_foreign\_library/1 is adjusted to call the already  
existing install function of the extension.

- WASM: Added calling JavaScript from Prolog, exchange DOM elements  
and adding scripts from Prolog.

- WASM: Renamed js\_call/1 to js\_run\_script/1 for consistency

- WASM: Avoid the need for a frame in Prolog.query(String).

- WASM: Provide Prolog.message\_to\_string()

- WASM: Allow a frame to discard all data

- WASM: Many changes to calling Prolog from JavaScript. These patches  
work to more high level interaction with Prolog from JavaScript.  
This work should be considered experimental.

- WASM: Perform UTF-8 decoding on output such that we can write Unicode.

- WASM: Handle sleep/1 using JavaScript setTimeout()

- WASM: Allow \_ in file names.

- WASM: Reduce auto-yield frequency and avoid the event loop when \< 20ms.

- WASM: Focus on input next/stop when requested.

- WASM: Set default package list to plunit, chr and clpqr

- WASM: Extended shell.html demo. Working asynchronous behavior, command  
line history and persistent files in localStorage and manage files.

- WASM: Many extensions to calling Prolog from JavaScript. Added support  
for (auto) yielding to achieve asynchronous behaviour in the browser.

- ADDED: heartbeat mechanism: by setting the Prolog flag `heartbeat`, the  
multifile predicate prolog:heartbeat/0 is called every _N_ inferences.

- FIXED: PL\_yield\_address() (foreign yielding) effectively popped one  
level of the foreign frame stack.

- WASM: Updated instructions in CMAKE.md. “Native friend” is no  
longer needed.

- WASM: Pass `-s ALLOW_MEMORY_GROWTH=1` to allow for bigger stacks.

- WASM: libswipl should not be a dynamic library on emscripten

- WASM: Attempt to support threads. Compiles, but doesn’t work on  
either Firefox or node.

- WASM: Addes js\_call/1 to call JavaScript

- WIP: trying to deal with reading.

- WASM: added `ttymode()` to Prolog JavaScript API.

- WASM: Minimal running example.

- CLEANUP: Type safety of property enumerators

- CLEANUP: get rid of function pointers without declared arguments.

- WASM: Make init argv default

- WASM: Put file system as /swipl and make this the Prolog home.

- WASM: Avoid absolute path messages when linking swipl-web

- FIXED: autoloading: read the module header using operators from the  
system module to avoid user operator declarations to cause a failure  
reading this.

- ENHANCED: Performance tuneup - reduce number of arithmetic operations  
for pivot - replace one call to lists:member/2 with memberchk/2

- ENHANCED: Optimize nth1/3 using ‘$seek\_list’/4

- DOC: Add =\> to the operator table.

## Package RDF

- PORT: Make library(rdf\_write) work without the RDF db.

## Package bdb

- PORT: Support static linking

## Package chr

- WASM: Install generated files in `wasm-preload`

## Package clib

- TEST: Synchronize libraries included and tests included. Also includes  
library(filesex) into the Emscripten version.

- PORT: Windows executable files may not have read access if they are  
a _reparse point_.

- FIXED: relative\_file\_name(Dir, SameDir, Rel) to return Rel as `.`  
rather than `''`.

- TEST: Disable tests that need threads on the single threaded version.

- WASM: Re-group plugins to make it easier to select only those that  
do not depend on OS features.

- PORT: Replace old K&R declarations

## Package http

- TEST: Synchronize installed and tested packages.

- DOC: http\_open/3: missing docs due to empty line.

- WASM: Provide a stripped down version for the WASM target, currently  
providing the library(http/html\_write), the json and stream library.

- ADDED: Mime type mappsing from `.data` to  
`application/octet-stream`.

- ADDED: MIME type rules: added .wasm → application/wasm.

## Package ltx2htm

- PORT: Allow for static linking

## Package mqi

- DOC: hard links to swipl manual

- DOC: hard links to swipl manual the “section references” do not get  
connected properly

- FIXED: Residual constraints on variables are now returned in a special  
binding variable called ‘$residuals’ MQI Prolog change only, no  
changes to the language clients (e.g. the swiplserver Python library)  
are required.

```plaintext
result = client.query("member(X, [A, B, C]),
put_attr(X, my_module, x).")
[{'$residuals': [{'args': ['A', 'my_module', 'x'],
'functor': 'put_attr'}], 'X': 'A', 'A': 'A', 'B':
'_', 'C': '_'},
{'$residuals': [{'args': ['B', 'my_module', 'x'],
'functor': 'put_attr'}], 'X': 'B', 'A': '_', 'B':
'B', 'C': '_'},
{'$residuals': [{'args': ['C', 'my_module', 'x'],
'functor': 'put_attr'}], 'X': 'C', 'A': '_', 'B':
'_', 'C': 'C'}] == result

```

- FIXED: If exceptions happen during serialization to JSON, MQI will  
now send an exception message instead of hanging

## Package semweb

- TEST: Make tests work in restricted single threaded version.

- BUILD: add cmake dependency

- PORT: Make the turtle and ntriples readers and writers load without  
library(semweb/rdf\_db). Still issues using them.

- PORT: Do build build `library(semweb/rdf_db)` in single threaded  
mode. In this mode the semweb only provides the turtle and ntriple  
readers and writers.

## Package sgml

- CLEANUP: Avoid function pointers with incomplete prototypes and make  
the install function follow the conventions to allow for statically  
linked extensions.

## Package ssl

- FIXED: Zero the PL\_CRYPTO\_HASH\_CONTEXT struct on first allocation

## Package xpce

- TEST: Create files and directories in temp.

- PORT: Avoid using Windows stat()

## Package zlib

- TEST: Disable socket based tests if sockets are not supported.

---

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**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\
**Post date:** [September 7, 2022, 11:37am UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-5-16/5749/2 "2022-09-07T11:37:09Z")

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Did you want to include #wasm\_demo in the announcement?

---

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**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:** [September 7, 2022, 12:09pm UTC](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-5-16/5749/3 "2022-09-07T12:09:22Z")

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Not necessarily. It’s been advertised enough.