* src/module-env-27.h: Add new module functions to convert big
integers.

* src/emacs-module.h.in (emacs_mpz): Define if GMP is available.

* src/emacs-module.c (module_extract_big_integer)
(module_make_big_integer): New functions.
(initialize_environment): Use them.

* test/data/emacs-module/mod-test.c (Fmod_test_double): New test
function.
(emacs_module_init): Define it.

* test/src/emacs-module-tests.el (mod-test-double): New unit test.

* doc/lispref/internals.texi (Module Values): Document new functions.

Time values are a fundamental data type, and such conversions are hard
to implement within modules because of the various forms of time
values in Emacs Lisp.  Adding dedicated conversion functions can
significantly simplify module code dealing with times.

This approach uses nanosecond precision.  While Emacs in theory has
support for higher-precision time values, in practice most languages
and standards, such as POSIX, C, Java, and Go, have settled on
nanosecond-precision integers to represent time.

* src/emacs-module.h.in: Add header for struct timespec.

* src/module-env-27.h: Add module functions for time conversion.

* src/emacs-module.c (module_extract_time, module_make_time): New
functions.
(initialize_environment): Use them.

* test/data/emacs-module/mod-test.c (Fmod_test_add_nanosecond): New
test function.
(emacs_module_init): Define it.

* test/src/emacs-module-tests.el (mod-test-add-nanosecond/valid)
(mod-test-add-nanosecond/nil, mod-test-add-nanosecond/invalid): New
unit tests.

* doc/lispref/internals.texi (Module Values): Document time
conversion functions.

This reverts commit 64d0cd98.

Rationale: any font-related code and comments, even if unused
for decades, serves as important source of useful information
in an area of Emacs code that is notoriously under-documented.

Please do NOT remove this stuff until we have an active
expert in this are on board, who will then decide whether
this can be retired.

* configure.ac: Check cairo early.  Don't try Xft if cairo is used.
* lwlib/lwlib-utils.h [USE_CAIRO]: Include cairo.h and fontconfig.h.
(XftFont, XftDraw, XftColor, XGlyphInfo) [USE_CAIRO]: New typedefs.
(XftFontOpenName, XftFontClose, XftDrawCreate, XftDrawDestroy)
(XftDrawRect, XftDrawStringUtf8, XftTextExtentsUtf8) [USE_CAIRO]: New macros.
(crxft_font_open_name, crxft_font_close, crxft_draw_create)
(crxft_draw_rect, crxft_draw_string, crxft_text_extents) [USE_CAIRO]: New
externs.
* lwlib/lwlib-utils.c [USE_CAIRO]: Include math.h, cairo-ft.h, and
cairo-xlib.h.
(crxft_font_open_name, crxft_font_close, crxft_draw_create)
(crxft_set_source_color, crxft_draw_rect, crxft_draw_string)
(crxft_text_extents) [USE_CAIRO]: New Xft compatibility functions.
* lwlib/xlwmenuP.h [USE_CAIRO]: Include lwlib-utils.h.
* lwlib/xlwmenu.c (display_menu_item) [USE_CAIRO]: Call
cairo_surface_mark_dirty and cairo_surface_flush.
* lwlib/lwlib-Xaw.c [USE_CAIRO]: Include stdlib.h and lwlib-utils.h.
(draw_text) [USE_CAIRO]: Call cairo_surface_flush.
* src/xsettings.c [USE_CAIRO]: Include fontconfig.h
(apply_xft_settings) [!HAVE_XFT]: Don't call XftDefaultSubstitute or
XftDefaultSet.
* lwlib/lwlib-Xaw.c:
* lwlib/lwlib-int.h:
* lwlib/xlwmenu.c:
* lwlib/xlwmenuP.h:
* src/xrdb.c:
* src/xsettings.c:
* src/xterm.c: Replace all #ifdef HAVE_XFT with #if defined USE_CAIRO ||
defined HAVE_XFT.
* src/xfns.c (x_default_font_parameter): Replace #ifdef HAVE_XFT with #if
defined	USE_CAIRO || defined HAVE_XFT.

Enable lexical-binding.
(cl-print-compiled, cl-print-compiled-button): Declare.
(timer-list-mode): Add spacing to align the header.

These directives are in files that are compiled only if the
symbols are defined.
* src/gfilenotify.c: Remove unnecessary ‘#ifdef HAVE_GFILENOTIFY’.
* src/inotify.c: Remove unnecessary ‘#ifdef HAVE_INOTIFY’.
* src/kqueue.c: Remove unnecessary ‘#ifdef HAVE_KQUEUE’.

* src/font.c (LSTRING_HEADER_SIZE, LSTRING_GLYPH_SIZE, check_gstring)
(check_otf_features, otf_list, otf_tag_symbol, otf_open)
(font_otf_capability, generate_otf_features)
(font_otf_DeviceTable, font_otf_ValueRecord)
(font_otf_Anchor, Ffont_drive_otf, Ffont_otf_alternates)
(Fdraw_string, syms_of_font): Remove "experimental and not
tested much" code that has been "#if 0"-ed out for more than a
decade and which was getting in the way of maintenance.

This provides more debugging hints for callers.

* src/emacs-module.c (module_copy_string_contents): Use three-argument
form of args-out-of-range.

INT_TO_INTEGER is more obviously correct and means we don’t have to
worry about data type sizes and signedness.

* src/json.c (json_parse_error): Use INT_TO_INTEGER.  The tiny
performance gain of make_fixed_natnum isn’t worth the trouble then
signaling an error.

* lisp/autorevert.el
(auto-revert-notify-watch-descriptor-hash-list):
Rename to auto-revert--buffers-by-watch-descriptor.  Improved doc string.
(auto-revert-notify-rm-watch, auto-revert-notify-add-watch,
auto-revert-notify-handler): Use new name.

* doc/lispref/processes.texi (Asynchronous Processes):
(Accepting Output): Remote processes cannot use a pipe process for
stderr.

Thanks to Dmitry Gutov <dgutov@yandex.ru> for running many
benchmarks and for useful discussions.
* src/json.c (json_make_string): Speed up parsing of JSON
strings by optimizing the normal case of a valid UTF-8 string
being returned from libjansson.  (Bug#31138)

* test/src/json-tests.el (json-parse-string/null): Make JSON object
syntactically valid.  This test is supposed to check whether an
escaped null character causes an error, but without quoting the string
it would be syntactically invalid in any case.

* lisp/progmodes/cc-fonts.el (c-font-lock-complex-decl-prepare)
(c-font-lock-objc-methods) (c-font-lock-declarations, c-font-lock-enum-tail)
(c-font-lock-cut-off-declarators, c-font-lock-enclosing-decls): If the chunk
been fontified consists entirely of comments and strings, don't attempt to
perform the function's action.

* lisp/progmodes/cc-mode.el (c-before-change-check-unbalanced-strings): Don't
expand (c-new-BEG c-new-END) unnecessarily to the entire raw string being
fontified.
(c-fl-decl-start, c-fl-decl-end): When in a (raw or otherwise) string, don't
return a position outside of the string (which used to cause unneeded
fontification).

* lwlib/lwlib-int.h (struct _widget_instance) [HAVE_XFT]: Remove nr_xft_data.
* lwlib/lwlib-Xaw.c (find_xft_data, xaw_update_one_widget) [HAVE_XFT]: Loop
while widget member is not NULL instead of using nr_xft_data.
(xaw_destroy_instance) [HAVE_XFT]: Move xft_data release code from here ...
(destroy_xft_data) [HAVE_XFT]: ... to here.
(make_dialog) [HAVE_XFT]: Add destroy_xft_data as destroy callback for dialog.

* Makefile.in (top_distclean): Clean makefile as well as Makefile.
* configure.ac: If not using plain ‘make’, create a makefile
so that plain ‘make’ simply calls $(MAKE).

Stefan Monnier pointed out examples like (funcall `(closure
,(let ((cycle (list nil))) (setcdr cycle cycle)) () a)),
where the user can set Vinternal_interpreter_environment
indirectly.
* src/eval.c (Fsetq): Revert recent change, going back to Fassq.

* etc/DEBUG: Improve -gdwarf-N documentation.
Go into more detail about UndefinedBehaviorSanitizer.

* src/eval.c (Fsetq, eval_sub): Use assq_no_quit instead
of Fassq for a list that cannot contain cycles or be that long.

* src/conf_post.h (__has_attribute_warn_unused_result):
New macro for compilers lacking __has_attribute.
* src/systhread.h (__has_attribute): Remove ineffective define.
(ATTRIBUTE_WARN_UNUSED_RESULT): Work better on GCC 3.4 thru 4.

Although the lisp.h macros really need improvement,
INTEGER_TO_INT is not the right way to go about it, as it
causes conversion from intmax_t to uintmax_t and back again,
which can cause a signal if the value is negative.
* src/lisp.h (INTEGER_TO_INT, ranged_integer_to_int)
(ranged_integer_to_uint): Remove, reverting recent changes to
this file.
* src/json.c (lisp_to_json): Revert to previous code,
as the change messes up with uintmax_t<->intmax_t conversion.

* lisp/autorevert.el (auto-revert-notify-handler):
When getting a `stopped' event, deal with it for the buffers it applies to,
rather than for all buffers in auto-revert mode.

This reverts commit e9e807e9,
which is no longer necessary as `file-notify-rm-watch' has been
made robust against reentry.

Allow file-notify callbacks to call `file-notify-rm-watch', harmlessly,
after receiving a `stopped' event without triggering recursion.

* lisp/filenotify.el (file-notify--watch): Note that `callback' can be nil.
(file-notify--rm-descriptor): Set the `callback' field to nil before
sending `stopped'.
(file-notify-rm-watch): Don't do anything if the `callback' field is nil.

This is similar to CONS_TO_INTEGER.  The inverse (INT_TO_INTEGER)
already exists.

* src/lisp.h (INTEGER_TO_INT): New macro.
(ranged_integer_to_int, ranged_integer_to_uint): New
functions.

* src/json.c (lisp_to_json): Use helper macro.

* doc/lispref/processes.texi (Asynchronous Processes): Document
existence and properties of the standard error process.
(Accepting Output): Document that one has to accept output from the
standard error process separately.

* emacs-module.c (module_make_string): Use make_unibyte_string, which
doesn’t require its argument to be null-terminated.  Since it always
returns a heap-allocated string, we don’t have to copy it any more
while decoding.
(module_decode): New helper function.

Factor out conversions into helper functions to provide a simpler
interface.

* src/emacs-module.c (module_encode, module_decode_copy): New helper
functions.
(module_make_function, module_copy_string_contents)
(module_make_string): Use them.

For discussion, see thread starting at:
https://lists.gnu.org/archive/html/emacs-devel/2019-04/msg00316.html
* doc/lispref/customize.texi (Composite Types): Do not overspecify
:match-alternatives predicates.
* doc/lispref/eval.texi (Intro Eval): Anchor definition of "side
effect" for cross-referencing...
* doc/lispref/functions.texi (What Is a Function): ...from here.
Define what a pure function is.
* doc/lispref/internals.texi (Writing Emacs Primitives): Describe
currently preferred approach to marking primitives as pure and
side-effect-free.
* doc/lispref/symbols.texi (Standard Properties): Expand description
of pure and side-effect-free properties.

Now that CATCHER_ALL catches signals as well, we can simplify
MODULE_HANDLE_NONLOCAL_EXIT a bit.

* src/emacs-module.c (MODULE_SETJMP, MODULE_SETJMP_1): Remove.
(MODULE_HANDLE_NONLOCAL_EXIT): Inline MODULE_SETJMP and
MODULE_SETJMP_1.

* test/lisp/net/tramp-tests.el (tramp-test32-shell-command):
Check for backward compatibility.
(tramp-test33-environment-variables): Apply a better check for
unset variable.

* etc/DEBUG: Modernize for AddressSanitizer etc.
* etc/NEWS: Defer to etc/DEBUG for this.

It doesn’t work anymore, and these days ‘gcc -fsanitize=address’
does a better job anyway.
* configure.ac: Remove the option.
* configure.ac (ac_xmalloc_overrun, XMALLOC_OVERRUN_CHECK):
* src/alloc.c (XMALLOC_OVERRUN_CHECK_OVERHEAD)
(XMALLOC_OVERRUN_CHECK_SIZE, XMALLOC_OVERRUN_SIZE_SIZE)
(xmalloc_overrun_check_header, xmalloc_overrun_check_trailer)
(xmalloc_put_size, xmalloc_get_size, overrun_check_malloc)
(overrun_check_realloc, overrun_check_free):
Remove.  All uses removed.
* etc/NEWS: Mention this.

* configure.ac: Remove the option.
* configure.ac (ac_gc_check_cons_list, GC_CHECK_CONS_LIST):
* src/alloc.c (check_cons_list) [GC_CHECK_CONS_LIST]:
* src/lisp.h (lisp_h_check_cons_list, check_cons_list):
Remove.  All uses removed.
* etc/NEWS: Mention this.