Convert the core lexer and parser into fully reentrant code, by making use

of features added to flex and bison since this code was originally written.
This change doesn't in itself offer any new capability, but it's needed
infrastructure for planned improvements in plpgsql.

Another feature now available in flex is the ability to make it use palloc
instead of malloc, so do that to avoid possible memory leaks.  (We should
at some point change the other lexers likewise, but this commit doesn't
touch them.)

1 files changed, 50 insertions, 48 deletions

diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 1e7f93af536..cb8ff8a3394 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -14,7 +14,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parser.c,v 1.79 2009/07/12 17:12:34 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parser.c,v 1.80 2009/07/13 02:02:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -25,14 +25,6 @@
 #include "parser/parser.h"
 
 
-List	   *parsetree;			/* result of parsing is left here */
-
-static bool have_lookahead;		/* is lookahead info valid? */
-static int	lookahead_token;	/* one-token lookahead */
-static YYSTYPE lookahead_yylval;	/* yylval for lookahead token */
-static YYLTYPE lookahead_yylloc;	/* yylloc for lookahead token */
-
-
 /*
  * raw_parser
  *		Given a query in string form, do lexical and grammatical analysis.
@@ -42,22 +34,29 @@ static YYLTYPE lookahead_yylloc;	/* yylloc for lookahead token */
 List *
 raw_parser(const char *str)
 {
+	base_yyscan_t yyscanner;
+	base_yy_extra_type yyextra;
 	int			yyresult;
 
-	parsetree = NIL;			/* in case grammar forgets to set it */
-	have_lookahead = false;
+	/* initialize the flex scanner */
+	yyscanner = scanner_init(str, &yyextra);
+
+	/* filtered_base_yylex() only needs this much initialization */
+	yyextra.have_lookahead = false;
 
-	scanner_init(str);
-	parser_init();
+	/* initialize the bison parser */
+	parser_init(&yyextra);
 
-	yyresult = base_yyparse();
+	/* Parse! */
+	yyresult = base_yyparse(yyscanner);
 
-	scanner_finish();
+	/* Clean up (release memory) */
+	scanner_finish(yyscanner);
 
 	if (yyresult)				/* error */
 		return NIL;
 
-	return parsetree;
+	return yyextra.parsetree;
 }
 
 
@@ -69,25 +68,27 @@ raw_parser(const char *str)
  * passed string does represent one single string literal.
  *
  * We export this function to avoid having plpgsql depend on internal details
- * of the core grammar (such as the token code assigned to SCONST).  Note
- * that since the scanner isn't presently re-entrant, this cannot be used
- * during use of the main parser/scanner.
+ * of the core grammar (such as the token code assigned to SCONST).
  */
 char *
 pg_parse_string_token(const char *token)
 {
+	base_yyscan_t yyscanner;
+	base_yy_extra_type yyextra;
 	int			ctoken;
+	YYSTYPE		yylval;
+	YYLTYPE		yylloc;
 
-	scanner_init(token);
+	yyscanner = scanner_init(token, &yyextra);
 
-	ctoken = base_yylex();
+	ctoken = base_yylex(&yylval, &yylloc, yyscanner);
 
 	if (ctoken != SCONST)		/* caller error */
 		elog(ERROR, "expected string constant, got token code %d", ctoken);
 
-	scanner_finish();
+	scanner_finish(yyscanner);
 
-	return base_yylval.str;
+	return yylval.str;
 }
 
 
@@ -105,23 +106,24 @@ pg_parse_string_token(const char *token)
  * layer does.
  */
 int
-filtered_base_yylex(void)
+filtered_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, base_yyscan_t yyscanner)
 {
+	base_yy_extra_type *yyextra = pg_yyget_extra(yyscanner);
 	int			cur_token;
 	int			next_token;
 	YYSTYPE		cur_yylval;
 	YYLTYPE		cur_yylloc;
 
 	/* Get next token --- we might already have it */
-	if (have_lookahead)
+	if (yyextra->have_lookahead)
 	{
-		cur_token = lookahead_token;
-		base_yylval = lookahead_yylval;
-		base_yylloc = lookahead_yylloc;
-		have_lookahead = false;
+		cur_token = yyextra->lookahead_token;
+		*lvalp = yyextra->lookahead_yylval;
+		*llocp = yyextra->lookahead_yylloc;
+		yyextra->have_lookahead = false;
 	}
 	else
-		cur_token = base_yylex();
+		cur_token = base_yylex(lvalp, llocp, yyscanner);
 
 	/* Do we need to look ahead for a possible multiword token? */
 	switch (cur_token)
@@ -131,9 +133,9 @@ filtered_base_yylex(void)
 			/*
 			 * NULLS FIRST and NULLS LAST must be reduced to one token
 			 */
-			cur_yylval = base_yylval;
-			cur_yylloc = base_yylloc;
-			next_token = base_yylex();
+			cur_yylval = *lvalp;
+			cur_yylloc = *llocp;
+			next_token = base_yylex(lvalp, llocp, yyscanner);
 			switch (next_token)
 			{
 				case FIRST_P:
@@ -144,13 +146,13 @@ filtered_base_yylex(void)
 					break;
 				default:
 					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
+					yyextra->lookahead_token = next_token;
+					yyextra->lookahead_yylval = *lvalp;
+					yyextra->lookahead_yylloc = *llocp;
+					yyextra->have_lookahead = true;
 					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
+					*lvalp = cur_yylval;
+					*llocp = cur_yylloc;
 					break;
 			}
 			break;
@@ -160,9 +162,9 @@ filtered_base_yylex(void)
 			/*
 			 * WITH TIME must be reduced to one token
 			 */
-			cur_yylval = base_yylval;
-			cur_yylloc = base_yylloc;
-			next_token = base_yylex();
+			cur_yylval = *lvalp;
+			cur_yylloc = *llocp;
+			next_token = base_yylex(lvalp, llocp, yyscanner);
 			switch (next_token)
 			{
 				case TIME:
@@ -170,13 +172,13 @@ filtered_base_yylex(void)
 					break;
 				default:
 					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
+					yyextra->lookahead_token = next_token;
+					yyextra->lookahead_yylval = *lvalp;
+					yyextra->lookahead_yylloc = *llocp;
+					yyextra->have_lookahead = true;
 					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
+					*lvalp = cur_yylval;
+					*llocp = cur_yylloc;
 					break;
 			}
 			break;