[WEB] Add Pascal TWILL 4.5.

See 'git log' in https://github.com/ascherer/twill (now 'archived') and
in https://github.com/ascherer/web (both branches 'master' and
'adapt-twill-for-texlive') for details of this impromptu project.

git-svn-id: svn://tug.org/texlive/trunk@61509 c570f23f-e606-0410-a88d-b1316a301751

8 files changed, 1068 insertions, 7 deletions

diff --git a/Build/source/texk/web2c/ChangeLog b/Build/source/texk/web2c/ChangeLog
index 92fadf21048..1ad6232e8e6 100644
--- a/Build/source/texk/web2c/ChangeLog
+++ b/Build/source/texk/web2c/ChangeLog
@@ -1,3 +1,11 @@
+2022-01-06  Andreas Scherer  <https://ascherer.github.io>
+
+	* Makefile.in,
+	* am/web.am,
+	* help.h,
+	* twill.test,
+	* weav-twill.ch: Add TWILL 4.5.
+
 2021-12-26  Andreas Scherer  <https://ascherer.github.io>
 
 	* ctangleboot.cin,
diff --git a/Build/source/texk/web2c/Makefile.in b/Build/source/texk/web2c/Makefile.in
index 6da432d88d7..da828ebd3ca 100644
--- a/Build/source/texk/web2c/Makefile.in
+++ b/Build/source/texk/web2c/Makefile.in
@@ -438,7 +438,7 @@ am__EXEEXT_1 = bibtex$(EXEEXT) dvicopy$(EXEEXT) dvitype$(EXEEXT) \
 	gftodvi$(EXEEXT) gftopk$(EXEEXT) gftype$(EXEEXT) mft$(EXEEXT) \
 	patgen$(EXEEXT) pktogf$(EXEEXT) pktype$(EXEEXT) \
 	pltotf$(EXEEXT) pooltype$(EXEEXT) tftopl$(EXEEXT) \
-	vftovp$(EXEEXT) vptovf$(EXEEXT) weave$(EXEEXT)
+	vftovp$(EXEEXT) vptovf$(EXEEXT) weave$(EXEEXT) twill$(EXEEXT)
 am__EXEEXT_2 = pbibtex$(EXEEXT) pdvitype$(EXEEXT) ppltotf$(EXEEXT) \
 	ptftopl$(EXEEXT)
 am__EXEEXT_3 = upbibtex$(EXEEXT) updvitype$(EXEEXT) uppltotf$(EXEEXT) \
@@ -1695,6 +1695,10 @@ nodist_weave_OBJECTS = weave.$(OBJEXT)
 weave_OBJECTS = $(nodist_weave_OBJECTS)
 weave_LDADD = $(LDADD)
 weave_DEPENDENCIES = $(proglib) $(am__DEPENDENCIES_1)
+nodist_twill_OBJECTS = twill.$(OBJEXT)
+twill_OBJECTS = $(nodist_twill_OBJECTS)
+twill_LDADD = $(LDADD)
+twill_DEPENDENCIES = $(proglib) $(am__DEPENDENCIES_1)
 nodist_wofm2opl_OBJECTS = ofm2opl.$(OBJEXT)
 wofm2opl_OBJECTS = $(nodist_wofm2opl_OBJECTS)
 wofm2opl_LDADD = $(LDADD)
@@ -1846,9 +1850,9 @@ am__depfiles_remade = ./$(DEPDIR)/aleph-aleph-pool.Po \
 	./$(DEPDIR)/uptex-uptex-pool.Po ./$(DEPDIR)/uptex-uptex0.Po \
 	./$(DEPDIR)/uptex-uptexini.Po ./$(DEPDIR)/uptftopl-uptftopl.Po \
 	./$(DEPDIR)/vftovp.Po ./$(DEPDIR)/vptovf.Po \
-	./$(DEPDIR)/weave.Po ./$(DEPDIR)/xetex-dummy.Po \
-	./$(DEPDIR)/xetex-xetex-pool.Po ./$(DEPDIR)/xetex-xetex0.Po \
-	./$(DEPDIR)/xetex-xetexini.Po \
+	./$(DEPDIR)/weave.Po ./$(DEPDIR)/twill.Po \
+	./$(DEPDIR)/xetex-dummy.Po ./$(DEPDIR)/xetex-xetex-pool.Po \
+	./$(DEPDIR)/xetex-xetex0.Po ./$(DEPDIR)/xetex-xetexini.Po \
 	alephdir/$(DEPDIR)/aleph-aleph.Po \
 	alephdir/$(DEPDIR)/aleph-alephbis.Po \
 	alephdir/$(DEPDIR)/aleph-alephextra.Po \
@@ -2557,6 +2561,7 @@ SOURCES = $(libff_a_SOURCES) $(libkanji_a_SOURCES) \
 	$(nodist_uptex_SOURCES) $(uptftopl_SOURCES) \
 	$(nodist_uptftopl_SOURCES) $(nodist_vftovp_SOURCES) \
 	$(nodist_vptovf_SOURCES) $(nodist_weave_SOURCES) \
+	$(nodist_twill_SOURCES) \
 	$(nodist_wofm2opl_SOURCES) $(nodist_wopl2ofm_SOURCES) \
 	$(nodist_wovf2ovp_SOURCES) $(nodist_wovp2ovf_SOURCES) \
 	$(dist_xetex_SOURCES) $(nodist_xetex_SOURCES) \
@@ -2791,7 +2796,7 @@ RECHECK_LOGS = $(TEST_LOGS)
 am__EXEEXT_44 = bibtex.test dvicopy.test dvitype.test gftodvi.test \
 	gftopk.test gftype.test mft.test patgen.test pktogf.test \
 	pktype.test pltotf.test pooltype.test tftopl.test vftovp.test \
-	vptovf.test weave.test
+	vptovf.test weave.test twill.test
 am__EXEEXT_45 = $(am__EXEEXT_44) tests/bibtex-openout-test.pl \
 	tests/bibtex-longline-test.pl tests/bibtex-mem.test \
 	tests/bibtex-bigauth.test tests/bibtex-auxinclude.test
@@ -3798,7 +3803,8 @@ ctangleboot = AM_V_P=$(AM_V_P) $(SHELL) ./ctangleboot-sh $@
 nodist_ctangleboot_SOURCES = ctangleboot.c cwebboot.c
 ctangleboot_DEPENDENCIES = $(default_dependencies)
 web_programs = bibtex dvicopy dvitype gftodvi gftopk gftype mft \
-	patgen pktogf pktype pltotf pooltype tftopl vftovp vptovf weave
+	patgen pktogf pktype pltotf pooltype tftopl vftovp vptovf \
+	weave twill
 
 web_tests = $(web_programs:=.test) tests/bibtex-openout-test.pl \
 	tests/bibtex-longline-test.pl tests/bibtex-mem.test \
@@ -3820,6 +3826,7 @@ nodist_tftopl_SOURCES = tftopl.c tftopl.h
 nodist_vftovp_SOURCES = vftovp.c vftovp.h
 nodist_vptovf_SOURCES = vptovf.c vptovf.h
 nodist_weave_SOURCES = weave.c weave.h
+nodist_twill_SOURCES = twill.c twill.h
 nodist_ctie_SOURCES = ctie.c
 nodist_cweave_SOURCES = cweave.c cweb.c
 nodist_ctwill_SOURCES = ctwill.c cweb.c
@@ -8327,6 +8334,10 @@ weave$(EXEEXT): $(weave_OBJECTS) $(weave_DEPENDENCIES) $(EXTRA_weave_DEPENDENCIE
 	@rm -f weave$(EXEEXT)
 	$(AM_V_CCLD)$(LINK) $(weave_OBJECTS) $(weave_LDADD) $(LIBS)
 
+twill$(EXEEXT): $(twill_OBJECTS) $(twill_DEPENDENCIES) $(EXTRA_twill_DEPENDENCIES)
+	@rm -f twill$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(twill_OBJECTS) $(twill_LDADD) $(LIBS)
+
 wofm2opl$(EXEEXT): $(wofm2opl_OBJECTS) $(wofm2opl_DEPENDENCIES) $(EXTRA_wofm2opl_DEPENDENCIES) 
 	@rm -f wofm2opl$(EXEEXT)
 	$(AM_V_CCLD)$(LINK) $(wofm2opl_OBJECTS) $(wofm2opl_LDADD) $(LIBS)
@@ -8571,6 +8582,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/vftovp.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/vptovf.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/weave.Po@am__quote@ # am--include-marker
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/twill.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/xetex-dummy.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/xetex-xetex-pool.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/xetex-xetex0.Po@am__quote@ # am--include-marker
@@ -19922,6 +19934,7 @@ distclean: distclean-recursive
 	-rm -f ./$(DEPDIR)/vftovp.Po
 	-rm -f ./$(DEPDIR)/vptovf.Po
 	-rm -f ./$(DEPDIR)/weave.Po
+	-rm -f ./$(DEPDIR)/twill.Po
 	-rm -f ./$(DEPDIR)/xetex-dummy.Po
 	-rm -f ./$(DEPDIR)/xetex-xetex-pool.Po
 	-rm -f ./$(DEPDIR)/xetex-xetex0.Po
@@ -20702,6 +20715,7 @@ maintainer-clean: maintainer-clean-recursive
 	-rm -f ./$(DEPDIR)/vftovp.Po
 	-rm -f ./$(DEPDIR)/vptovf.Po
 	-rm -f ./$(DEPDIR)/weave.Po
+	-rm -f ./$(DEPDIR)/twill.Po
 	-rm -f ./$(DEPDIR)/xetex-dummy.Po
 	-rm -f ./$(DEPDIR)/xetex-xetex-pool.Po
 	-rm -f ./$(DEPDIR)/xetex-xetex0.Po
@@ -21548,6 +21562,15 @@ weave-web2c: weave.p $(web2c_depend)
 weave.p: tangle$(EXEEXT) weave.web weave.ch
 	$(tangle) weave weave
 weave.log: weave$(EXEEXT)
+twill.c twill.h: twill-web2c
+	@$(web2c) twill
+twill-web2c: twill.p $(web2c_depend)
+	@$(web2c) twill
+twill.p: tangle$(EXEEXT) twill.web
+	$(tangle) twill
+twill.log: twill$(EXEEXT)
+twill.web: tie$(EXEEXT) weave.web weave.ch weav-twill.ch
+	$(tie_m) weave.web weave.ch weav-twill.ch
 ctie.c: ctangle$(EXEEXT) ctiedir/ctie.w ctiedir/ctie-k.ch
 	$(ctangle_silent)CWEBINPUTS=$(srcdir)/ctiedir $(ctangle) ctie.w ctie-k.ch
 cweave.c: ctangle$(EXEEXT) cwebdir/comm-w2c.h cwebdir/cweave.w cwebdir/prod-cweave.w cwebdir/cweav-w2c.ch
diff --git a/Build/source/texk/web2c/am/web.am b/Build/source/texk/web2c/am/web.am
index 6bb25aebba2..c7d700373c6 100644
--- a/Build/source/texk/web2c/am/web.am
+++ b/Build/source/texk/web2c/am/web.am
@@ -7,7 +7,8 @@
 ## You may freely use, modify and/or distribute this file.
 
 web_programs = bibtex dvicopy dvitype gftodvi gftopk gftype mft \
-	patgen pktogf pktype pltotf pooltype tftopl vftovp vptovf weave
+	patgen pktogf pktype pltotf pooltype tftopl vftovp vptovf \
+	weave twill
 
 ## Basic tests, one for each program.
 ##
@@ -174,6 +175,17 @@ weave.p: tangle$(EXEEXT) weave.web weave.ch
 	$(tangle) weave weave
 weave.log: weave$(EXEEXT)
 
+nodist_twill_SOURCES = twill.c twill.h
+twill.c twill.h: twill-web2c
+	@$(web2c) twill
+twill-web2c: twill.p $(web2c_depend)
+	@$(web2c) twill
+twill.p: tangle$(EXEEXT) twill.web
+	$(tangle) twill
+twill.web: tie$(EXEEXT) weave.web weave.ch weav-twill.ch
+	$(tie_m) weave.web weave.ch weav-twill.ch
+twill.log: twill$(EXEEXT)
+
 ## Tests.
 ##
 if WEB
diff --git a/Build/source/texk/web2c/help.h b/Build/source/texk/web2c/help.h
index 4779ce298a8..55181d50f6d 100644
--- a/Build/source/texk/web2c/help.h
+++ b/Build/source/texk/web2c/help.h
@@ -639,4 +639,18 @@ const_string WEAVEHELP[] = {
 };
 #endif /* WEAVE */
 
+#ifdef TWILL
+const_string TWILLHELP[] = {
+    "Usage: twill [OPTION]... WEBFILE[.web] [CHANGEFILE[.ch]]",
+    "  Weave WEBFILE with CHANGEFILE into a TeX document.",
+    "  Default CHANGEFILE is " DEV_NULL ";",
+    "  TeX output goes to the basename of WEBFILE extended with `.tex'.",
+    "",
+    "-x          omit cross-reference information",
+    "-help       display this help and exit",
+    "-version    output version information and exit",
+    NULL
+};
+#endif /* TWILL */
+
 #endif /* not HELP_H */
diff --git a/Build/source/texk/web2c/twill.test b/Build/source/texk/web2c/twill.test
new file mode 100755
index 00000000000..eeaa3a56730
--- /dev/null
+++ b/Build/source/texk/web2c/twill.test
@@ -0,0 +1,12 @@
+#! /bin/sh -vx
+# $Id$
+# Copyright 2022 Andreas Scherer <https://ascherer.github.io>
+# Copyright 2017 Karl Berry <tex-live@tug.org>
+# Copyright 2009 Peter Breitenlohner <tex-live@tug.org>
+# You may freely use, modify and/or distribute this file.
+
+test -d tests || mkdir -p tests
+
+TEXMFCNF=$srcdir/../kpathsea WEBINPUTS=$srcdir \
+  ./twill pooltype || exit 1
+
diff --git a/Build/source/texk/web2c/weav-twill.ch b/Build/source/texk/web2c/weav-twill.ch
new file mode 100644
index 00000000000..cf8a96996be
--- /dev/null
+++ b/Build/source/texk/web2c/weav-twill.ch
@@ -0,0 +1,987 @@
+Changes for WEAVE.WEB to mogrify WEAVE into TWILL.
+
+See the 'git log' in https://github.com/ascherer/twill and
+https://github.com/ascherer/web for details.
+
+Public domain.  Originally written by Andreas Scherer, 2022.
+
+Limbo.
+
+@x 2,29c2,5
+% Version 0 was released in December, 1981.
+% Version 1 was released in September, 1982, with version 0 of TeX.
+% Slight changes were made in October, 1982, for version 0.6 of TeX.
+% Version 1.1 changed "_" to "\_" if not within an identifier (November, 1982).
+% Version 1.2 added @@= and @@\ and marked changed modules (December, 1982).
+% Version 1.3 marked and indexed changed modules better (January, 1983).
+% Version 1.4 added "history" (February, 1983).
+% Version 1.5 conformed to TeX version 0.96 (March, 1983).
+% Version 1.6 conformed to TeX version 0.98 (May, 1983).
+% Version 1.7 introduced the new change file format (June, 1983).
+% Version 2 was released in July, 1983, with version 0.999 of TeX.
+% Version 2.1 corrected a bug in changed_module reckoning (August, 1983).
+% Version 2.2 corrected it better (August, 1983).
+% Version 2.3 starts the output with \input webmac (August, 1983).
+% Version 2.4 fixed a bug in compress(#) (September, 1983).
+% Version 2.5 cleared xrefswitch after module names (November, 1983).
+% Version 2.6 fixed a bug in declaration of trans array (January, 1984).
+% Version 2.7 fixed a bug in real constants (August, 1984).
+% Version 2.8 fixed a bug in change_buffer movement (August, 1985).
+% Version 2.9 increased max_refs and max_toks to 30000 each (January, 1987).
+% Version 3, for Sewell's book, fixed long-line bug in input_ln (March, 1989).
+% Version 3.1 fixed a bug for programs with only one module (April, 1989).
+% Version 4 was major change to allow 8-bit input (September, 1989).
+% Version 4.1, for Breitenlohner, avoids English-only output (March, 1990).
+% Version 4.2 conforms to ANSI standard for-loop rules (September, 1990).
+% Version 4.3 catches extra } in input (Breitenlohner, September, 1991).
+% Version 4.4 corrects changed_module logic, %-overflow (January, 1992).
+% Version 4.5 corrects archaic @@z logic and empty change file (January, 2021).
+@y
+% But it is not polished either, so you probably shouldn't try....
+% Version 2.8 (based on WEAVE 2.8) was hacked together on 28 Sep 1985.
+% Version 2.9 fixed output for dtype_string (14 Jun 1987).
+% Version 4.5 (based on WEAVE 4.5) was hacked together on 04 Jan 2022.
+@z
+
+@x 48c24
+  \centerline{\titlefont The {\ttitlefont WEAVE} processor}
+@y
+  \centerline{\titlefont The {\ttitlefont TWILL} processor}
+@z
+
+@x 43c19
+\let\maybe=\iffalse
+\def\title{WEAVE changes for C}
+@y
+\let\maybe=\iftrue
+\def\title{TWILL for \TeX~Live}
+@z
+
+Section 1.
+
+@x 54a31,35
+@* Introduction.
+@y
+@* Introduction.
+[Apology: This modification of \.{WEAVE} was put together hastily at the
+end of September, 1985, in order to prepare the listing of \TeX,
+on the WAITS system. No attempt has been made to polish anything
+or to make this code usable by anyone else but its author.]
+
+@z
+
+@x 77c58
+@d banner=='This is WEAVE, Version 4.5'
+@y
+@d banner=='This is TWILL, Version 4.5'
+@z
+
+Section 8.
+
+@x 203a185
+@!stack_size=2000; {number of simultaneous output levels}
+@y
+@!stack_size=2000; {number of simultaneous output levels}
+@!max_new_refs=200; {number of different references to other modules}
+@z
+
+Section 37.
+
+@x 742a725
+@!xref: array [0..max_names] of sixteen_bits; {heads of cross-reference lists}
+@y
+@!xref: array [0..max_names] of sixteen_bits; {heads of cross-reference lists}
+@!def_val: array [0..max_names] of integer; {values of numeric macros}
+@z
+
+Section 46.
+
+@x 889a873,876
+@d xlink(#)==xmem[#].xlink_field
+@y
+@d xlink(#)==xmem[#].xlink_field
+@d dtype(#)==xmem[#].dtype_field
+@d dname(#)==xmem[#].dname_field
+@d dback(#)==xmem[#].dback_field
+@d dlink(#)==xmem[#].dlink_field
+@z
+
+Section 48.
+
+@x 895c882,899
+@ @<Globals...@>=
+@y
+@ Definitions are classified into 15 types.
+@d dtype_none=0
+@d dtype_macro=1
+@d dtype_const=2
+@d dtype_string=3
+@d dtype_colon_bold=4
+@d dtype_equal_bold=5
+@d dtype_colon_packed=6
+@d dtype_equal_packed=7
+@d dtype_colon_ital=8
+@d dtype_equal_ital=9
+@d dtype_comma=10
+@d dtype_colon_const_dots=11
+@d dtype_equal_const_dots=12
+@d dtype_colon_ital_dots=13
+@d dtype_equal_ital_dots=14
+
+@<Globals...@>=
+@z
+
+@x 898a903,906
+  @!xlink_field: sixteen_bits; {pointer to the previous cross reference}
+@y
+  @!xlink_field: sixteen_bits; {pointer to the previous cross reference}
+  @!dtype_field: sixteen_bits; {type of definition}
+  @!dname_field: sixteen_bits; {identifier or constant}
+  @!dback_field: sixteen_bits; {if nonzero, this is a reference to name}
+  @!dlink_field: sixteen_bits; {link to definitions only}
+@z
+
+@x 901a910,912
+@!xref_switch,@!mod_xref_switch:0..def_flag; {either zero or |def_flag|}
+@y
+@!xref_switch,@!mod_xref_switch:0..def_flag; {either zero or |def_flag|}
+@!def_type,@!def_name,@!def_subtype,@!def_subname,
+  @!const_name,@!packed_name:integer;
+@!danger_zone:boolean;
+@z
+
+Section 49.
+
+@x 903a915
+@ @<Set init...@>=xref_ptr:=0; xref_switch:=0; mod_xref_switch:=0; num(0):=0;
+@y
+@ @<Set init...@>=xref_ptr:=0; xref_switch:=0; mod_xref_switch:=0; num(0):=0;
+danger_zone:=false;
+@z
+
+Section 50.
+
+@x 908a...
+to one-letter identifiers or \PASCAL's reserved words.
+@y
+to one-letter identifiers or \PASCAL's reserved words.
+
+The |new_blank_xref| is similar but it ignores the |xref_switch|.
+@z
+
+@x 911a924
+  else  begin incr(xref_ptr); num(xref_ptr):=#;
+@y
+  else  begin incr(xref_ptr); num(xref_ptr):=#;
+    dback(xref_ptr):=0;
+@z
+
+@x 925,926c938,942
+    begin num(q):=m; return;
+    end;
+@y
+    if (def_type>=dtype_comma) or danger_zone then
+      q:=xlink(q) {delete entry}
+    else begin num(q):=m; dtype(q):=def_type;
+      dname(q):=def_name; dback(q):=p; return;
+      end;
+@z
+
+@x 928,929c945,952
+append_xref(m); xlink(xref_ptr):=q; xref[p]:=xref_ptr;
+exit: end;
+@y
+append_xref(m); xlink(xref_ptr):=q; xref[p]:=xref_ptr;
+if m>def_flag then
+  begin dtype(xref_ptr):=def_type; dname(xref_ptr):=def_name;
+  dback(xref_ptr):=p;
+  if def_type>dtype_comma then
+    begin append_xref(0); dtype(xref_ptr):=def_subtype;
+    dname(xref_ptr):=def_subname;
+    end;
+  end;
+exit: end;
+@#
+procedure new_blank_xref(@!p:integer);
+var xs:integer;
+begin xs:=xref_switch; xref_switch:=0; new_xref(p); xref_switch:=xs;
+end;
+@z
+
+Section 62.
+
+@x 1064a1096,1097
+@ When we begin the following segment of the program, |p=name_ptr|.
+@y
+@ When we begin the following segment of the program, |p=name_ptr|.
+
+@d undef_val==10000000
+
+@z
+
+@x 1074c1107
+ilk[p]:=t; xref[p]:=0;
+@y
+ilk[p]:=t; xref[p]:=0; def_val[p]:=undef_val;
+@z
+
+Section 64.
+
+@x 1112c1145
+id5("c")("o")("n")("s")("t")(const_like);@/
+@y
+id5("c")("o")("n")("s")("t")(const_like); const_name:=cur_name;@/
+@z
+
+@x 1130c1163
+id6("p")("a")("c")("k")("e")("d")(goto_like);@/
+@y
+id6("p")("a")("c")("k")("e")("d")(goto_like); packed_name:=cur_name;@/
+@z
+
+Section 71.
+
+@x 1278,1279d1310
+@!change_pending: boolean; {if |true|, the current change is not yet
+  recorded in |changed_module[module_count]|}
+@y
+@z
+
+Section 79.
+
+@x 1371,1383d1401
+When a match is found, the current module is marked as changed unless
+the first line after the \.{@@x} and after the \.{@@y} both start with
+either |'@@*'| or |'@@ '| (possibly preceded by whitespace).
+
+@d if_module_start_then_make_change_pending(#)==
+  loc:=0; buffer[limit]:="!";
+  while (buffer[loc]=" ")or(buffer[loc]=tab_mark) do incr(loc);
+  buffer[limit]:=" ";
+  if buffer[loc]="@@" then
+    if (buffer[loc+1]="*") or
+       (buffer[loc+1]=" ") or (buffer[loc+1]=tab_mark) then
+      change_pending:=#
+
+@y
+@z
+
+@x 1389,1393d1406
+change_pending:=false;
+if not changed_module[module_count] then
+  begin if_module_start_then_make_change_pending(true);
+  if not change_pending then changed_module[module_count]:=true;
+  end;
+@y
+@z
+
+Section 82.
+
+@x 1450,1454c1463,1469
+begin restart:if changing then
+  @<Read from |change_file| and maybe turn off |changing|@>;
+if not changing then
+  begin @<Read from |web_file| and maybe turn on |changing|@>;
+  if changing then goto restart;
+@y
+begin restart: if changing then changed_module[module_count]:=true
+else  @<Read from |web_file| and maybe turn on |changing|@>;
+if changing then
+  begin @<Read from |change_file| and maybe turn off |changing|@>;
+  if not changing then
+    begin changed_module[module_count]:=true; goto restart;
+    end;
+@z
+
+Section 83.
+
+@x 1462c1477,1479
+else if change_limit>0 then check_change;
+@y
+else if limit=change_limit then
+  if buffer[0]=change_buffer[0] then
+    if change_limit>0 then check_change;
+@z
+
+Section 84.
+
+@x 1472,1479c1489
+if limit>0 then {check if the change has ended}
+  begin if change_pending then
+    begin if_module_start_then_make_change_pending(false);
+    if change_pending then
+      begin changed_module[module_count]:=true; change_pending:=false;
+      end;
+    end;
+  buffer[limit]:=" ";
+@y
+if limit>1 then {check if the change has ended}
+@z
+
+@x 1491d1500
+  end;
+@y
+@z
+
+Section 88.
+
+@x 1594a1604,1606
+"0","1","2": begin tracing:=c-"0"; control_code:=ignore;
+@y
+"0","1","2": begin tracing:=c-"0"; control_code:=ignore;
+"3": begin @{'*****************************************************'@}
+  control_code:=ignore; {to set a breakpoint}
+  end;
+@z
+
+Section 110.
+
+@x 1965c2032
+changed_module[module_count]:=changing;
+@y
+changed_module[module_count]:=false;
+@z
+
+Section 111.
+
+@x 1991c...
+@p procedure Pascal_xref; {makes cross references for \PASCAL\ identifiers}
+@y
+@p @<Functions |scan_const| and |scan_exp|@>
+@#
+procedure Pascal_xref; {makes cross references for \PASCAL\ identifiers}
+@z
+
+@x 1992c2059
+label exit;
+@y
+label exit,done,found,not_found;
+@z
+
+@x 1993a2061
+var p:name_pointer; {a referenced name}
+@y
+var p:name_pointer; {a referenced name}
+@!eq:0..3; {addition to |dtype| code}
+@z
+
+@x 1997c2065,2069
+    begin p:=id_lookup(next_control-identifier); new_xref(p);
+@y
+    begin p:=id_lookup(next_control-identifier);
+    if next_control=identifier then if xref_switch<>0 then if ilk[p]=normal then
+      @<Figure out the |def_type| and |def_name|, etc.@>;
+    new_xref(p);
+    danger_zone:=(def_type=dtype_comma);
+@z
+
+@x 1999a2072,2078
+      xref_switch:=def_flag; {implied `\.{@@!}'}
+@y
+      xref_switch:=def_flag; {implied `\.{@@!}'}
+    if ilk[p]=proc_like then
+      begin def_name:=p; next_control:=get_next;
+      if next_control<>identifier then goto done;
+      if xref_switch=0 then goto done;
+      p:=id_lookup(normal); def_type:=dtype_colon_bold;
+      new_xref(p);
+      end;
+@z
+
+@x 2002c2081
+  if (next_control="|")or(next_control="{") then return;
+@y
+done:  if (next_control="|")or(next_control="{") then return;
+@z
+
+Section 115.
+
+@x 2061c2208,2226
+  if next_control=definition then next_control:=get_next
+@y
+  if next_control=definition then
+    begin next_control:=get_next;
+    if next_control=identifier then
+      begin lhs:=id_lookup(normal);
+      next_control:=get_next;
+      if (next_control=equivalence_sign)or(next_control="(") then
+        begin def_type:=dtype_macro; new_xref(lhs);
+        end
+      else if next_control="=" then
+        begin xref_switch:=0; next_control:=get_next;
+        def_val[lhs]:=scan_exp;
+        def_name:=def_val[lhs]; def_type:=dtype_const;
+        xref_switch:=def_flag;
+        if abs(def_name)>=32768 then def_type:=dtype_macro
+        else if def_name<0 then def_name:=def_name+65536;
+        new_xref(lhs);
+        end;
+      end;
+    end
+@z
+
+Section 124.
+
+@x 2199,2201c2364
+`\.{\\input webmac}'.
+@.\\input webmac@>
+@.webmac@>
+@y
+`\.{\\input twimac}'.
+@.\\input twimac@>
+@.twimac@>
+@z
+
+@x 2204c2367
+out_ptr:=1; out_line:=1; out_buf[1]:="c"; write(tex_file,'\input webma');
+@y
+out_ptr:=1; out_line:=1; out_buf[1]:="c"; write(tex_file,'\input twima');
+@z
+
+Section 125.
+
+@x 2219a2383,2389
+@d oot5(#)==oot(#)@,oot4
+@y
+@d oot5(#)==oot(#)@,oot4
+@d oot6(#)==oot(#)@,oot5
+@d oot7(#)==oot(#)@,oot6
+@d oot8(#)==oot(#)@,oot7
+@d oot9(#)==oot(#)@,oot8
+@d oot10(#)==oot(#)@,oot9
+@d oot11(#)==oot(#)@,oot10
+@d oot12(#)==oot(#)@,oot11
+@z
+
+@x 2224a2395,2401
+@d out5==@+begin oot5
+@y
+@d out5==@+begin oot5
+@d out6==@+begin oot6
+@d out7==@+begin oot7
+@d out8==@+begin oot8
+@d out9==@+begin oot9
+@d out10==@+begin oot10
+@d out11==@+begin oot11
+@d out12==@+begin oot12
+@z
+
+Section 130.
+
+@x 2273c...
+@ The number to be converted by |out_mod| is known to be less than
+|def_flag|, so it cannot have more than five decimal digits.  If
+the module is changed, we output `\.{\\*}' just after the number.
+@y
+@ The number to be converted by |out_mod| is known to be less than
+|def_flag|, so it cannot have more than five decimal digits.
+@z
+
+@x 2285d
+if changed_module[m] then out2("\")("*");
+@.\\*@>
+@y
+@z
+
+Section 133.
+
+@x 2333,2334c2510,2512
+  out("@@");
+  if c<>"@@" then err_print('! Double @@ required outside of sections');
+@.Double \AT! required...@>
+@y
+  if (c<>"z")and(c<>"Z") then
+    begin out("@@");
+    if c<>"@@" then err_print('! Double @@ required outside of sections');
+@.Double \AT! required...@>
+    end;
+@z
+
+Section 183.
+
+@x 3522a3702
+@!p:name_pointer; {identifier designator}
+@y
+@!p:name_pointer; {identifier designator}
+@!q,@!qq,@!r:integer; {registers for new reference insertion loop}
+@z
+
+Section 191.
+
+@x 3698a3879
+begin p:=id_lookup(normal);
+@y
+begin p:=id_lookup(normal);
+if ilk[p]=normal then @<Insert a new reference, if this is new@>;
+@z
+
+Section 197.
+
+@x 3816c...
+@p function Pascal_translate: text_pointer;
+@y
+@d flaky=1
+@d guaranteed=0
+
+@p function Pascal_translate: text_pointer;
+@z
+@x 3819c4033
+begin save_base:=scrap_base; scrap_base:=scrap_ptr+1;
+@y
+begin save_base:=scrap_base; scrap_base:=scrap_ptr+1; safety:=flaky;
+@z
+
+@x 3827c4041
+Pascal_translate:=p;
+@y
+safety:=guaranteed; Pascal_translate:=p;
+@z
+
+Section 218.
+
+@x 4226c4440
+module_count:=0;
+@y
+module_count:=0; xx:=0;
+@z
+
+@x 4228a4443
+finish_line; flush_buffer(0,false,false); {insert a blank line, it looks nice}
+@y
+finish_line; flush_buffer(0,false,false); {insert a blank line, it looks nice}
+@<Prepare high-speed access to definitions via |dlink| and |def_val|@>;
+@z
+
+Section 220.
+
+@x 4249a4492,4493
+begin incr(module_count);@/
+@y
+begin incr(module_count);@/
+mm:=module_count+def_flag; ref_link[0]:=0; ref_loc[0]:=0; new_ref_ptr:=0;
+safety:=guaranteed;
+@z
+
+Section 236.
+
+@x 4503a4749
+if flag=0 then out("U")@+else out("A");
+@y
+if flag=0 then out("U")@+else out("A");
+out8(" ")("s")("e")("c")("t")("i")("o")("n");
+@z
+
+@x 4514,4515c4760
+@.\\As@>
+@.\\Us@>
+@y
+out("~");
+@z
+
+Section 237.
+
+@x 4519,4524c4764,4767
+  if num(xlink(cur_xref))>flag then out2(",")(" ") {not the last}
+  else begin out3("\")("E")("T"); {the last}
+@.\\ET@>
+    if cur_xref<>xlink(q) then out("s"); {the last of more than two}
+@.\\ETs@>
+    end;
+@y
+  if (num(xlink(cur_xref))>flag)or(cur_xref<>xlink(q)) then out(",");
+    {not the last of two}
+  out(" ");
+  if num(xlink(cur_xref))<=flag then out4("a")("n")("d")("~"); {the last}
+@z
+
+Section 238.
+
+@x 4529c4772,4776
+out3("\")("f")("i"); finish_line;
+@y
+out6("\")("m")("i")("n")("i")("%");
+@.\\mini@>
+beta_out;
+flush_buffer(out_ptr,false,false);
+out4("}")("\")("F")("I"); finish_line;
+@z
+
+@x 4531c4778,4893
+@.\\fi@>
+@y
+@.\\FI@>
+@z
+
+Section 241.
+
+@x 4561a4924
+k_module:=1;
+@y
+k_module:=1;
+while not changed_module[k_module] do incr(k_module);
+@z
+
+@x 4563,4568d4925
+while k_module<module_count do
+  begin if changed_module[k_module] then
+    begin out_mod(k_module); out2(",")(" ");
+    end;
+  incr(k_module);
+  end;
+@y
+@z
+
+@x 4569a4927,4929
+out_mod(k_module);
+@y
+out_mod(k_module);
+repeat repeat incr(k_module)@+ until changed_module[k_module];
+  out2(",")(" "); out_mod(k_module);
+until k_module=module_count;
+@z
+
+Section 254.
+
+@x 4726c5086,5093
+if cur_val<def_flag then out_mod(cur_val)
+@y
+if cur_val<def_flag then
+  begin out_mod(cur_val);
+  if cur_val+1=num(xlink(cur_xref)) then
+    begin out2("-")("-");
+    repeat cur_xref:=xlink(cur_xref); incr(cur_val);
+    until cur_val+1<>num(xlink(cur_xref)); out_mod(cur_val);
+    end;
+  end
+@z
+
+Section 261.
+
+@x 4842c...
+@p procedure Phase_I;
+@y
+@p @<Functions |alpha_out|, |beta_out|, and helpers@>
+@#
+procedure Phase_I;
+@z
+
+@x 4846a5214
+procedure Phase_II;
+@y
+procedure Phase_II;
+var lhs:integer;
+@z
+
+Section 264.
+
+@x WEAVE.CH
+      usage_help (WEAVE_HELP, nil);
+@y
+      usage_help (TWILL_HELP, nil);
+@z
+
+@x
+@!web_name,@!chg_name,@!tex_name:const_c_string;
+@y
+@!web_name,@!chg_name,@!tex_name:const_c_string;
+
+@* New material for \.{TWILL}.
+Here's a new subroutine needed for \.{TWILL}. Assuming that |next_control|
+is the beginning of a numeric constant, and that string constants have
+length~1, the |scan_const| function returns the value of the constant
+and sets |next_control| to the following token.
+
+@<Functions |scan_const| and |scan_exp|@>=
+function scan_const:integer;
+label done;
+var radix,accum,p:integer;
+begin if next_control=string then
+  begin accum:=buffer[id_first+1]; next_control:=get_next; goto done;
+  end
+else if next_control=identifier then
+  begin p:=id_lookup(normal); new_blank_xref(p);
+  accum:=def_val[p]; next_control:=get_next; goto done;
+  end
+else  begin accum:=0;
+  if next_control=hex then radix:=16
+  else if next_control=octal then radix:=8
+  else  begin radix:=10; accum:=next_control-"0";
+    end;
+  loop  begin next_control :=get_next;
+    if next_control<"0" then goto done;
+    if radix=16 then
+      begin if (next_control>="A")and(next_control<="F") then
+        next_control:=next_control-"A"+"0"+10
+      else if next_control>"9" then goto done;
+      end
+    else if next_control>="0"+radix then goto done;
+    accum:=accum*radix+next_control-"0";
+    end;
+  end;
+done: scan_const:=accum;
+end;
+
+@ Simple linear arithmetic is handled by the following
+subroutine, which doesn't complain about certain syntactic errors.
+
+@d start_of_const(#)==(((#>="0")and(#<="9"))or(#=hex)or(#=octal)or(#=string)
+  or(#=identifier))
+@d sign(#)==(abs(#-",")=1)
+@d start_of_num(#)==(start_of_const(#)or sign(#))
+
+@<Functions |scan_const| and |scan_exp|@>=
+function scan_exp:integer;
+label done;
+var accum,s:integer;
+begin if sign(next_control) then accum:=0
+else accum:=scan_const;
+loop  begin if not sign(next_control) then goto done;
+  s:=","-next_control; next_control:=get_next;
+  if not start_of_const(next_control) then goto done;
+  accum:=accum+s*scan_const;
+  end;
+done:scan_exp:=accum;
+end;
+
+@ @d found_it(#)==begin def_type:=#; goto found; end
+
+@<Figure out the |def_type| and |def_name|, etc.@>=
+begin next_control:=get_next;
+if next_control="," then found_it(dtype_comma);
+if(next_control=":")or(next_control="=") then
+  @<Figure out a type and |goto| either |found| or |not_found|@>;
+not_found:def_type:=dtype_none; new_xref(p); goto done;
+found: end
+
+@ @<Figure out a type and...@>=
+begin eq:=(next_control-":") div ("="-":");
+next_control:=get_next;
+if next_control=identifier then
+  @<Figure out a type starting with an identifier;
+    |goto| |found| or |not_found| unless it's a subrange@>
+else if (next_control=string)and(id_loc-id_first>2) then found_it(dtype_string)
+else if start_of_num(next_control) then
+  @<Figure out a type starting with a constant;
+    |goto| |found| or |not_found| unless it's a subrange@>
+else goto not_found;
+next_control:=get_next;
+if next_control=identifier then
+  begin def_subname:=id_lookup(normal);
+  if ilk[def_subname]<>normal then goto not_found;
+  if def_val[def_subname]=undef_val then
+    begin new_blank_xref(def_subname);
+    def_subtype:=dtype_colon_ital_dots; goto found;
+    end;
+  end;
+if start_of_num(next_control) then
+  begin def_subname:=scan_exp; def_subtype:=dtype_colon_const_dots;
+  if abs(def_subname)>=32768 then goto not_found;
+  if def_subname<0 then def_subname:=def_subname+65536;
+  goto found;
+  end;
+goto not_found;
+end
+
+@ @<Figure out a type starting with an identifier...@>=
+begin def_name:=id_lookup(normal);
+if ilk[def_name]=goto_like then {\&{packed}}
+  begin next_control:=get_next; eq:=eq+2;
+  if next_control<>identifier then goto not_found;
+  def_name:=id_lookup(normal);
+  end;
+if (ilk[def_name]=array_like)or(ilk[def_name]=record_like) then
+  found_it(dtype_colon_bold+eq);
+if ilk[def_name]<>normal then goto found;
+new_blank_xref(def_name);
+if def_val[def_name]=undef_val then
+  begin next_control:=get_next;
+  if next_control=double_dot then def_type:=dtype_colon_ital_dots+eq
+  else found_it(dtype_colon_ital+eq);
+  end
+else @<Figure out a type starting with a constant...@>;
+end
+
+@ @<Figure out a type starting with a constant...@>=
+begin def_name:=scan_exp;
+if next_control<>double_dot then
+  if eq=1 then found_it(dtype_equal_bold; def_name:=const_name)
+  else goto not_found;
+if abs(def_name)>=32768 then goto not_found;
+if def_name<0 then def_name:=def_name+65536;
+def_type:=dtype_colon_const_dots+eq;
+end
+
+@ Some identifiers can be inserted during Phase II that weren't
+seen in Phase I (namely, if they appear only in module names);
+so we have to watch out that |def_val| might be |undef_val|.
+
+@<Insert a new reference, if this is new@>=
+begin q:=def_val[p];
+if q<>0 then if q<>undef_val then if not phase_three then
+  begin repeat r:=q; q:=dlink(q);
+  until (q=0) or (num(q)>mm);
+  if num(r)<>mm then
+    begin qq:=0; q:=ref_link[0];
+    while ref_loc[q]>r do
+      begin qq:=q; q:=ref_link[qq];
+      end;
+    if ref_loc[q]=r then
+      begin if safety=guaranteed then
+       if ref_safety[q]=flaky then ref_safety[q]:=guaranteed;
+      end
+    else  begin if new_ref_ptr=max_new_refs then overflow('new references');
+      incr(new_ref_ptr);
+      ref_link[new_ref_ptr]:=q; ref_link[qq]:=new_ref_ptr;
+      ref_loc[new_ref_ptr]:=r;
+      if dlink(def_val[p])=0 then ref_safety[new_ref_ptr]:=guaranteed
+      else ref_safety[new_ref_ptr]:=safety;
+      end;
+    end;
+  end;
+end
+
+@ @<Prepare high-speed access to definitions via |dlink| and |def_val|@>=
+for lhs:=1 to name_ptr do if ilk[lhs]=normal then
+  begin def_val[lhs]:=0; rhs:=xref[lhs];
+  while rhs<>0 do
+    begin if num(rhs)>def_flag then
+      begin dlink(rhs):=def_val[lhs];
+      def_val[lhs]:=rhs;
+      end;
+    rhs:=xlink(rhs);
+    end;
+  end
+
+@ We keep a separate list of all references made in the current module,
+sorted by |xref| number. A reference is considered to need manual checking
+if it appears only in a comment within the section and if the corresponding
+identifier is multiply defined.
+
+@<Glob...@>=
+@!mm:integer; {current module number plus |def_flag|}
+@!ref_loc:array[0..max_new_refs] of sixteen_bits;
+@!ref_link:array[0..max_new_refs] of sixteen_bits;
+@!ref_safety:array[0..max_new_refs] of guaranteed..flaky;
+@!new_ref_ptr:0..max_new_refs;
+@!safety:guaranteed..flaky;
+@!xx:xref_number;
+
+@ The |alpha_out| procedure makes entries for all identifiers defined
+in the current module. (However, I no longer need these!)
+
+@<Functions |alpha_out|, |beta_out|, and helpers@>=
+procedure alpha_out;
+label exit;
+var p,w,k:integer;
+begin loop begin
+  if xx=xref_ptr then return;
+  if num(xx+1)>mm then return;
+  incr(xx);
+        if num(xx)>def_flag then if dback(xx)>0 then
+   if ilk[dback(xx)]=normal then
+    begin flush_buffer(out_ptr,false,false);
+    out5("\")("m")("i")("n")("i");
+@.\\mini@>
+    p:=dback(xx);
+    w:=p mod ww;
+    for k:=byte_start[p] to byte_start[p+ww]-1 do out(byte_mem[w,k]);
+    if dtype(xx)>dtype_comma then incr(xx);
+    end;
+  end;
+exit:end;
+
+@ Here's a procedure that's very much like |out_mod|.
+
+@<Functions |alpha_out|, |beta_out|, and helpers@>=
+procedure out_const(@!n:sixteen_bits);
+var a,k:integer;
+begin a:=n; k:=0;
+if a>=32768 then
+  begin out("-"); a:=65536-a;
+  end;
+repeat dig[k]:=a mod 10; a:=a div 10; incr(k);
+until a=0;
+repeat decr(k); out(dig[k]+"0");
+until k=0;
+end;
+
+@ And here's something that could have been made a subroutine earlier.
+
+@<Functions |alpha_out|, |beta_out|, and helpers@>=
+procedure out_id(@!p:integer);
+begin out("\");
+if ilk[p]=normal then
+  if length(p)=1 then out("|")
+@.\\|@>
+  else out("\")
+@.\\\\@>
+else out("&");
+@.\\\&@>
+if length(p)=1 then out(byte_mem[p mod ww,byte_start[p]])
+else out_name(p);
+end;
+
+@ The |beta_out| procedure makes entries for all identifiers used
+but not defined in the current module.
+
+@<Functions |alpha_out|, |beta_out|, and helpers@>=
+procedure beta_out;
+label done,888,found;
+var k,p,q,w,xx,mmm:integer;
+begin p:=ref_link[0];
+while p<>0 do
+  begin flush_buffer(out_ptr,false,false);
+  out2("\")("[");
+  xx:=ref_loc[p]; q:=dback(xx); w:=q mod ww;
+  for k:=byte_start[q] to byte_start[q+ww]-1 do out(byte_mem[w,k]);
+  out(" "); out_const(num(xx)-def_flag);
+  out(" ");
+  @<Move past commas@>;
+  @<Output the reference, based on its |dtype|@>;
+  if ref_safety[p]=flaky then out3(" ")("%")("?");
+  p:=ref_link[p];
+  end;
+end;
+
+@ @<Output the reference, based on its |dtype|@>=
+case dtype(xx) of
+dtype_none: out5("\")("n")("o")("n")("e");
+dtype_macro: out6("=")("m")("a")("c")("r")("o");
+dtype_const: begin out2("=")("$"); out_const(dname(xx)); out("$");
+  end;
+dtype_string:
+  out12("\")(".")("{")("""")("s")("t")("r")("i")("n")("g")("""")("}");
+dtype_colon_bold,dtype_colon_ital: begin out(":"); out_id(dname(xx)); end;
+dtype_equal_bold,dtype_equal_ital: begin out("="); out_id(dname(xx)); end;
+dtype_colon_packed: begin out(":"); out_id(packed_name); out2("\")(" ");
+ out_id(dname(xx)); end;
+dtype_equal_packed: begin out("="); out_id(packed_name); out2("\")(" ");
+ out_id(dname(xx)); end;
+dtype_colon_const_dots: begin out2(":")("$"); out_const(dname(xx));
+ goto 888; end;
+dtype_equal_const_dots: begin out2("=")("$"); out_const(dname(xx));
+ goto 888; end;
+dtype_colon_ital_dots: begin out2(":")("$"); out_id(dname(xx)); goto 888; end;
+dtype_equal_ital_dots: begin out2("=")("$"); out_id(dname(xx)); goto 888; end;
+end; {there are no other cases}
+goto found;
+888: out3("\")("t")("o");
+ if dtype(xx+1)=dtype_colon_ital_dots then
+  out_id(dname(xx+1))
+ else out_const(dname(xx+1));
+ out("$");
+found:
+
+@ @<Move past commas@>=
+mmm:=num(xx);
+loop  begin if dtype(xx)<>dtype_comma then if num(xx)=mmm then goto done;
+  if xx=xref_ptr then
+    begin dtype(xx):=dtype_none; goto done;
+    end;
+  if num(xx+1)>mmm then
+    begin dtype(xx):=dtype_none; goto done;
+    end;
+  incr(xx);
+  end;
+done:
+@z
diff --git a/Build/source/texk/web2c/web2c/ChangeLog b/Build/source/texk/web2c/web2c/ChangeLog
index 0fb6f5cd16d..c77eed13c96 100644
--- a/Build/source/texk/web2c/web2c/ChangeLog
+++ b/Build/source/texk/web2c/web2c/ChangeLog
@@ -1,3 +1,7 @@
+2022-01-06  Andreas Scherer  <https://ascherer.github.io>
+
+	* common.defines: New TWILLHELP.
+
 2021-03-23  Karl Berry  <karl@tug.org>
 
 	* TL'21.
diff --git a/Build/source/texk/web2c/web2c/common.defines b/Build/source/texk/web2c/web2c/common.defines
index a848eb11b52..47fcf57e690 100644
--- a/Build/source/texk/web2c/web2c/common.defines
+++ b/Build/source/texk/web2c/web2c/common.defines
@@ -94,6 +94,7 @@
 @define const VFTOVPHELP;
 @define const VPTOVFHELP;
 @define const WEAVEHELP;
+@define const TWILLHELP;
 
 @define function abs ();
 @define function addressof ();