* data/Makefile.am (dist_pkgdata_DATA): Add push.c.

* data/c.m4 (YYPUSH): New.
(b4_push_if): New macro.  Use it instead of #ifdef YYPUSH.
* src/getargs.c (push_parser): New var.
* src/getargs.h (push_parser): New declaration.
* src/output.c (prepare): Add macro insertion of `push_flag'.
* src/parse-gram.y (PERCENT_PUSH_PARSER): New token.
(prologue_declaration): Parse %push-parser.
* src/scan-gram.l: Scan new PERCENT_PUSH_PARSER token.
* tests/calc.at (_AT_CHECK_CALC_ERROR): Add "Return" and "Now" to
list of removed lines from the traces observed.
(AT_CHECK_CALC_LALR): Added push parser tests.

src/getargs.c

@@ -59,6 +59,7 @@ bool error_verbose = false;
 bool nondeterministic_parser = false;
 bool glr_parser = false;
 bool pure_parser = false;
+bool push_parser = false;
 
 int report_flag = report_none;
 int trace_flag = trace_none;

src/getargs.h

@@ -53,6 +53,11 @@ extern bool glr_parser;
 
 extern bool pure_parser;
 
+/* PUSH_PARSER is true if should generate a parser that is capable of being
+   called asynchronously.  Is must be pure and reentrant.  */
+
+extern bool push_parser;
+
 /* NONDETERMINISTIC_PARSER is true iff conflicts are accepted.  This
    is used by the GLR parser, and might be used in BackTracking
    parsers too.  */

src/output.c

@@ -585,6 +585,7 @@ prepare (void)
   MUSCLE_INSERT_BOOL ("error_verbose_flag", error_verbose);
   MUSCLE_INSERT_BOOL ("locations_flag", locations_flag);
   MUSCLE_INSERT_BOOL ("pure_flag", pure_parser);
+  MUSCLE_INSERT_BOOL ("push_flag", push_parser);
   MUSCLE_INSERT_BOOL ("synclines_flag", !no_lines_flag);
   MUSCLE_INSERT_BOOL ("tag_seen_flag", tag_seen);
   MUSCLE_INSERT_BOOL ("yacc_flag", yacc_flag);

src/parse-gram.y

@@ -156,6 +156,7 @@ static int current_prec = 0;
   PERCENT_OUTPUT          "%output"
   PERCENT_PARSE_PARAM     "%parse-param"
   PERCENT_PURE_PARSER     "%pure-parser"
+  PERCENT_PUSH_PARSER     "%push-parser"
   PERCENT_REQUIRE	  "%require"
   PERCENT_SKELETON        "%skeleton"
   PERCENT_START           "%start"
@@ -248,6 +249,7 @@ prologue_declaration:
 | "%output" "=" STRING          { spec_outfile = $3; }
 | "%parse-param" "{...}"	{ add_param ("parse_param", $2, @2); }
 | "%pure-parser"                { pure_parser = true; }
+| "%push-parser"                { push_parser = true; }
 | "%require" STRING             { version_check (&@2, $2); }
 | "%skeleton" STRING            { skeleton = $2; }
 | "%start-header" braceless     { muscle_code_grow ("start_header", $2, @2); }

src/scan-gram.l

@@ -188,6 +188,7 @@ splice	 (\\[ \f\t\v]*\n)*
   "%prec"                 	    return PERCENT_PREC;
   "%printer"              	    return PERCENT_PRINTER;
   "%pure"[-_]"parser"     	    return PERCENT_PURE_PARSER;
+  "%push"[-_]"parser"		    return PERCENT_PUSH_PARSER;
   "%require"              	    return PERCENT_REQUIRE;
   "%right"                	    return PERCENT_RIGHT;
   "%skeleton"             	    return PERCENT_SKELETON;