function interface to parse Perl statement

yyparse() becomes reentrant.  The yacc stack and related resources
are allocated in yyparse(), rather than in lex_start(), and they are
localised to yyparse(), preserving their values from any outer parser.

yyparse() now takes a parameter which determines which production it
will parse at the top level.  New API function parse_fullstmt() uses this
facility to parse just a single statement.  The top-level single-statement
production that is used for this then messes with the parser's head so
that the parsing stops without seeing EOF, and any lookahead token seen
after the statement is pushed back to the lexer.

1 files changed, 26 insertions, 6 deletions

diff --git a/perly.c b/perly.c
index 3624ca3c04..3edf57da86 100644
--- a/perly.c
+++ b/perly.c
@@ -34,6 +34,9 @@ typedef unsigned short int yytype_uint16;
 typedef short int yytype_int16;
 typedef signed char yysigned_char;
 
+/* YYINITDEPTH -- initial size of the parser's stacks.  */
+#define YYINITDEPTH 200
+
 #ifdef DEBUGGING
 #  define YYDEBUG 1
 #else
@@ -195,7 +198,7 @@ S_clear_yystack(pTHX_  const yy_parser *parser)
     yy_stack_frame *ps     = parser->ps;
     int i = 0;
 
-    if (!parser->stack || ps == parser->stack)
+    if (!parser->stack)
 	return;
 
     YYDPRINTF ((Perl_debug_log, "clearing the parse stack\n"));
@@ -311,6 +314,8 @@ S_clear_yystack(pTHX_  const yy_parser *parser)
 	SvREFCNT_dec(ps->compcv);
 	ps--;
     }
+
+    Safefree(parser->stack);
 }
 
 
@@ -320,9 +325,9 @@ S_clear_yystack(pTHX_  const yy_parser *parser)
 
 int
 #ifdef PERL_IN_MADLY_C
-Perl_madparse (pTHX)
+Perl_madparse (pTHX_ int gramtype)
 #else
-Perl_yyparse (pTHX)
+Perl_yyparse (pTHX_ int gramtype)
 #endif
 {
     dVAR;
@@ -346,16 +351,31 @@ Perl_yyparse (pTHX)
 #ifndef PERL_IN_MADLY_C
 #  ifdef PERL_MAD
     if (PL_madskills)
-	return madparse();
+	return madparse(gramtype);
 #  endif
 #endif
 
     YYDPRINTF ((Perl_debug_log, "Starting parse\n"));
 
     parser = PL_parser;
-    ps = parser->ps;
 
-    ENTER;  /* force parser stack cleanup before we return */
+    ENTER;  /* force parser state cleanup/restoration before we return */
+    SAVEPPTR(parser->yylval.pval);
+    SAVEINT(parser->yychar);
+    SAVEINT(parser->yyerrstatus);
+    SAVEINT(parser->stack_size);
+    SAVEINT(parser->yylen);
+    SAVEVPTR(parser->stack);
+    SAVEVPTR(parser->ps);
+
+    /* initialise state for this parse */
+    parser->yychar = gramtype;
+    parser->yyerrstatus = 0;
+    parser->stack_size = YYINITDEPTH;
+    parser->yylen = 0;
+    Newx(parser->stack, YYINITDEPTH, yy_stack_frame);
+    ps = parser->ps = parser->stack;
+    ps->state = 0;
     SAVEDESTRUCTOR_X(S_clear_yystack, parser);
 
 /*------------------------------------------------------------.