graph: prefer *.gv to *.dot

Reported by Hans Åberg.
https://lists.gnu.org/archive/html/help-bison/2019-02/msg00064.html

* src/files.c (spec_graph_file): Use `*.gv` when 3.4 or better,
otherwise `*.dot`.
* src/parse-gram.y (handle_require): Pretend we are already 3.4.
* doc/bison.texi: Adjust.
* tests/local.at, tests/output.at: Exercise this.

NEWS

@@ -2,6 +2,12 @@ GNU Bison NEWS
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
+** Changes
+
+  In conformance with the recommendations of the GraphViz team, if %require
+  "3.4" (or better) is specified, the option --graph generates a *.gv file
+  by default, instead of *.dot.
+
 ** New features
 
 *** Disabling output
@@ -14,6 +20,9 @@ GNU Bison NEWS
   A new example in C shows an simple infix calculator with a hand-written
   scanner (examples/c/calc).
 
+  A new example in C shows a reentrant parser (capable of recursive calls)
+  built with Flex and Bison (examples/c/reccalc).
+
 * Noteworthy changes in release 3.3.2 (2019-02-03) [stable]
 
 ** Bug fixes

doc/bison.texi

@@ -4795,10 +4795,16 @@ status 63).
 @end example
 
 Some deprecated behaviors are disabled for some required @var{version}:
-@table @code
-@item "3.2"
+@table @asis
+@item @code{"3.2"} (or better)
 The C++ deprecated files @file{position.hh} and @file{stack.hh} are no
 longer generated.
+
+@item @code{"3.4"} (or better)
+To comply with the
+@uref{https://marc.info/?l=graphviz-devel&m=129418103126092, recommendations
+of the GraphViz team}, use the @code{.gv} extension instead of @code{.dot}
+for the name of the generated DOT file.  @xref{Graphviz}.
 @end table
 
 
@@ -6137,12 +6143,12 @@ start: FILE for ERROR;
 @end example
 
 @noindent
-generates the definition of the symbols @code{TOK_FILE}, @code{TOK_for},
-and @code{TOK_ERROR} in the generated source files.  In particular, the
-scanner must use these prefixed token names, while the grammar itself
-may still use the short names (as in the sample rule given above).  The
-generated informational files (@file{*.output}, @file{*.xml},
-@file{*.dot}) are not modified by this prefix.
+generates the definition of the symbols @code{TOK_FILE}, @code{TOK_for}, and
+@code{TOK_ERROR} in the generated source files.  In particular, the scanner
+must use these prefixed token names, while the grammar itself may still use
+the short names (as in the sample rule given above).  The generated
+informational files (@file{*.output}, @file{*.xml}, @file{*.gv}) are not
+modified by this prefix.
 
 Bison also prefixes the generated member names of the semantic value union.
 @xref{Type Generation,, Generating the Semantic Value Type}, for more
@@ -9732,8 +9738,8 @@ to help them understand LR parsers.
 This file is generated when the @option{--graph} option is specified
 (@pxref{Invocation, , Invoking Bison}).  Its name is made by removing
 @samp{.tab.c} or @samp{.c} from the parser implementation file name, and
-adding @samp{.dot} instead.  If the grammar file is @file{foo.y}, the
-Graphviz output file is called @file{foo.dot}.  A DOT file may also be
+adding @samp{.gv} instead.  If the grammar file is @file{foo.y}, the
+Graphviz output file is called @file{foo.gv}.  A DOT file may also be
 produced via an XML file and XSLT processing (@pxref{Xml,,Visualizing your
 parser in multiple formats}).
 
@@ -10767,12 +10773,12 @@ described under the @samp{-v} and @samp{-d} options.
 
 @item -g [@var{file}]
 @itemx --graph[=@var{file}]
-Output a graphical representation of the parser's
-automaton computed by Bison, in @uref{http://www.graphviz.org/, Graphviz}
+Output a graphical representation of the parser's automaton computed by
+Bison, in @uref{http://www.graphviz.org/, Graphviz}
 @uref{http://www.graphviz.org/doc/info/lang.html, DOT} format.
-@code{@var{file}} is optional.
-If omitted and the grammar file is @file{foo.y}, the output file will be
-@file{foo.dot}.
+@code{@var{file}} is optional.  If omitted and the grammar file is
+@file{foo.y}, the output file will be @file{foo.gv} if the @code{%required}
+version is 3.4 or better, @file{foo.dot} otherwise.
 
 @item -x [@var{file}]
 @itemx --xml[=@var{file}]

src/files.c

@@ -342,7 +342,8 @@ compute_output_file_names (void)
   if (graph_flag)
     {
       if (! spec_graph_file)
-        spec_graph_file = concat2 (all_but_tab_ext, ".dot");
+        spec_graph_file = concat2 (all_but_tab_ext,
+                                   304 <= required_version ? ".gv" : ".dot");
       output_file_name_check (&spec_graph_file, false);
     }
 

src/parse-gram.c

@@ -3463,10 +3463,9 @@ handle_require (location const *loc, char const *version)
       return;
     }
   required_version = major * 100 + minor;
-  /* Pretend to be at least 3.2, even if we are only 3.1-211, as it
-     allows us to check features published in 3.2 while developping
-     3.2.  */
-  const char* api_version = "3.2";
+  /* Pretend to be at least 3.4, to check features published in 3.4
+     while developping it.  */
+  const char* api_version = "3.4";
   const char* package_version =
     strverscmp (api_version, PACKAGE_VERSION) > 0
     ? api_version : PACKAGE_VERSION;

src/parse-gram.y

@@ -958,10 +958,9 @@ handle_require (location const *loc, char const *version)
       return;
     }
   required_version = major * 100 + minor;
-  /* Pretend to be at least 3.2, even if we are only 3.1-211, as it
-     allows us to check features published in 3.2 while developping
-     3.2.  */
-  const char* api_version = "3.2";
+  /* Pretend to be at least 3.4, to check features published in 3.4
+     while developping it.  */
+  const char* api_version = "3.4";
   const char* package_version =
     strverscmp (api_version, PACKAGE_VERSION) > 0
     ? api_version : PACKAGE_VERSION;

tests/.gitignore

@@ -1,8 +1,6 @@
-/*.dot
 /*.output
 /atconfig
 /atlocal
-/autom4te.cache
 /bison
 /calc
 /calc.[chy]

tests/local.at

@@ -752,7 +752,7 @@ m4_define([AT_BISON_CHECK_XML],
   # Don't combine these Bison invocations since we want to be sure that
   # --report=all isn't required to get the full XML file.
   AT_BISON_CHECK_([[--report=all --report-file=xml-tests/test.output \
-             --graph=xml-tests/test.dot ]]AT_BISON_ARGS,
+             --graph=xml-tests/test.gv ]]AT_BISON_ARGS,
            [[0]], [ignore], [ignore])
   AT_BISON_CHECK_([[--xml=xml-tests/test.xml ]]AT_BISON_ARGS,
            [[0]], [ignore], [ignore])
@@ -761,7 +761,7 @@ m4_define([AT_BISON_CHECK_XML],
   AT_CHECK([[$XSLTPROC \
              `]]AT_QUELL_VALGRIND[[ bison --print-datadir`/xslt/xml2text.xsl \
              xml-tests/test.xml]], [[0]], [expout])
-  [sort xml-tests/test.dot > expout]
+  [sort xml-tests/test.gv > expout]
   AT_CHECK([[$XSLTPROC \
              `]]AT_QUELL_VALGRIND[[ bison --print-datadir`/xslt/xml2dot.xsl \
              xml-tests/test.xml | sort]], [[0]], [expout])

tests/output.at

@@ -76,6 +76,8 @@ AT_CHECK_OUTPUT([foo.y], [], [-dv -o foo.tab.c],
 
 AT_CHECK_OUTPUT([foo.y], [], [-dv -g --xml -y],
                 [y.dot y.output y.tab.c y.tab.h y.xml])
+AT_CHECK_OUTPUT([foo.y], [%require "3.4"], [-dv -g --xml -y],
+                [y.gv y.output y.tab.c y.tab.h y.xml])
 # With '-o y.tab.c', we expect 'y.output' etc. (for compatibility with Yacc).
 AT_CHECK_OUTPUT([foo.y], [], [-dv -g --xml -o y.tab.c],
                 [y.dot y.output y.tab.c y.tab.h y.xml])