merge branch 'maint'

* upstream/maint:
  maint: post-release administrivia
  version 3.5.3
  news: update for 3.5.3
  yacc.c: make sure we properly propagated the user's number for error
  diagnostics: don't crash because of repeated definitions of error
  style: initialize some struct members
  diagnostics: beware of zero-width characters
  diagnostics: be sure to close the styling when lines are too short
  muscles: fix incorrect decoding of $
  code: be robust to reference with invalid tags
  build: fix typo
  doc: update recommandation for libtextstyle
  style: comment changes
  examples: use consistently the GFDL header for readmes
  style: remove useless declarations
  typo: succesful -> successful
  README: point to tests/bison, and document --trace
  gnulib: update
  maint: post-release administrivia

tests/diagnostics.at

@@ -37,15 +37,15 @@ AT_BISON_OPTION_PUSHDEFS
 
 AT_DATA_GRAMMAR([[input.y]], [$2])
 
+AT_DATA([experr], [$4])
+
 # For some reason, literal ^M in the input are removed and don't end
 # in `input.y`.  So use the two-character ^M represent it, and let
 # Perl insert real CR characters.
-if grep '\^M' input.y >/dev/null; then
-  AT_PERL_REQUIRE([-pi -e 's{\^M}{\r}gx' input.y])
+if $EGREP ['\^M|\\[0-9][0-9][0-9]'] input.y experr >/dev/null; then
+  AT_PERL_REQUIRE([-pi -e 's{\^M}{\r}g;s{\\(\d{3}|.)}{$v = $[]1; $v =~ /\A\d+\z/ ? chr($v) : $v}ge' input.y experr])
 fi
 
-AT_DATA([experr], [$4])
-
 AT_CHECK([LC_ALL="$locale" $5 bison -fcaret --color=debug -Wall input.y], [$3], [], [experr])
 
 # When no style, same messages, but without style.
@@ -152,6 +152,65 @@ input.y: <warning>warning:</warning> fix-its can be applied.  Rerun with option
 ]])
 
 
+
+## ------------------------------------- ##
+## Line is too short, and then you die.  ##
+## ------------------------------------- ##
+
+# We trust the "#line", since that's what allows us to quote the
+# actual source from which the gramar file was generated.  But #line
+# can also be wrong, and point to a line which is shorter that the bad
+# one.  In which case we can easily forget to close the styling.
+#
+# Be sure to have #line point to a line long enough to open the
+# styling, but not enough to close it.
+
+AT_TEST([[Line is too short, and then you die]],
+[[// Beware that there are 9 lines inserted before (including this one).
+#line 12
+%token foo 123
+%token foo 123123
+%token foo 123
+%%
+exp:
+]],
+[1],
+[[input.y:13.8-10: <warning>warning:</warning> symbol foo redeclared [<warning>-Wother</warning>]
+   13 | %token <warning>foo</warning> 123
+      |        <warning>^~~</warning>
+input.y:12.8-10: <note>note:</note> previous declaration
+   12 | %token <note>foo</note> 123123
+      |        <note>^~~</note>
+input.y:13.12-17: <error>error:</error> redefining user token number of foo
+   13 | %token foo <error>123</error>
+      |            <error>^~~~~~</error>
+input.y:14.8-10: <warning>warning:</warning> symbol foo redeclared [<warning>-Wother</warning>]
+   14 | %%
+      |        <warning>^~~</warning>
+input.y:12.8-10: <note>note:</note> previous declaration
+   12 | %token <note>foo</note> 123123
+      |        <note>^~~</note>
+]])
+
+
+## ----------------------- ##
+## Zero-width characters.  ##
+## ----------------------- ##
+
+# We used to open twice the styling for characters that have a
+# zero-width on display (e.g., \005).
+
+AT_TEST([[Zero-width characters]],
+[[%%
+exp: an\005error.
+]],
+[1],
+[[input.y:10.8: <error>error:</error> invalid character: '\\005'
+   10 | exp: an<error>\005</error>error.
+      |        <error>^</error>
+]])
+
+
 ## -------------------------------------- ##
 ## Tabulations and multibyte characters.  ##
 ## -------------------------------------- ##
@@ -262,7 +321,7 @@ input.y:10.1-27: <error>error:</error> %define variable 'error2' is not used
 ## ----------------- ##
 
 # Carriage-return used to count as a newline in the scanner, and not
-# in diagnostics.  Resulting in all sort of nice bugs.
+# in diagnostics.  Resulting in all kinds of nice bugs.
 
 AT_TEST([[Carriage return]],
 [[^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M^M