Make pgbench's expression lexer reentrant.

This is a necessary preliminary step for making it play with psqlscan.l
given the way I set up the lexer input-buffer sharing mechanism in commit
0ea9efbe9ec1bf07.

I've not tried to make it *actually* reentrant; there's still some static
variables laying about.  But flex thinks it's reentrant, and that's what
counts.

In support of that, fix exprparse.y to pass through the yyscan_t from the
caller.  Also do some minor code beautification, like not casting away
const.

1 files changed, 52 insertions, 31 deletions

diff --git a/src/bin/pgbench/exprscan.l b/src/bin/pgbench/exprscan.l
index fc7615f5585..00cb74d7dad 100644
--- a/src/bin/pgbench/exprscan.l
+++ b/src/bin/pgbench/exprscan.l
@@ -7,6 +7,8 @@
  * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
+ * src/bin/pgbench/exprscan.l
+ *
  *-------------------------------------------------------------------------
  */
 
@@ -16,16 +18,27 @@ static int	yyline = 0, yycol = 0;
 /* Handles to the buffer that the lexer uses internally */
 static YY_BUFFER_STATE scanbufhandle;
 static char *scanbuf;
-static int	scanbuflen;
 
 /* context information for error reporting */
-static char *expr_source = NULL;
+static const char *expr_source = NULL;
 static int expr_lineno = 0;
-static char *expr_full_line = NULL;
-static char *expr_command = NULL;
+static const char *expr_full_line = NULL;
+static const char *expr_command = NULL;
 static int expr_col = 0;
+
+/*
+ * Work around a bug in flex 2.5.35: it emits a couple of functions that
+ * it forgets to emit declarations for.  Since we use -Wmissing-prototypes,
+ * this would cause warnings.  Providing our own declarations should be
+ * harmless even when the bug gets fixed.
+ */
+extern int	expr_yyget_column(yyscan_t yyscanner);
+extern void expr_yyset_column(int column_no, yyscan_t yyscanner);
+
 %}
 
+/* Except for the prefix, these options should match psqlscan.l */
+%option reentrant
 %option 8bit
 %option never-interactive
 %option nodefault
@@ -42,6 +55,15 @@ space			[ \t\r\f]
 
 %%
 
+%{
+		/*
+		 * Force flex into the appropriate start state ... which, for this
+		 * case, is always INITIAL.  This ensures that we can transition
+		 * between different lexers sharing the same yyscan_t.
+		 */
+		BEGIN(INITIAL);
+%}
+
 "+"				{ yycol += yyleng; return '+'; }
 "-"				{ yycol += yyleng; return '-'; }
 "*"				{ yycol += yyleng; return '*'; }
@@ -69,77 +91,76 @@ space			[ \t\r\f]
 
 [\n]			{ yycol = 0; yyline++; }
 
-{space}+		{ yycol += yyleng; /* ignore */ }
+{space}+		{ yycol += yyleng; /* otherwise ignore */ }
 
 .				{
 					yycol += yyleng;
 					syntax_error(expr_source, expr_lineno, expr_full_line, expr_command,
 								 "unexpected character", yytext, expr_col + yycol);
-					/* dead code, exit is called from syntax_error */
-					return CHAR_ERROR;
+					/* NOTREACHED, exit is called from syntax_error */
+					return 0;
 				}
 %%
 
 void
-expr_yyerror_more(const char *message, const char *more)
+expr_yyerror_more(yyscan_t yyscanner, const char *message, const char *more)
 {
 	syntax_error(expr_source, expr_lineno, expr_full_line, expr_command,
 				 message, more, expr_col + yycol);
 }
 
 void
-yyerror(const char *message)
+yyerror(yyscan_t yyscanner, const char *message)
 {
-	expr_yyerror_more(message, NULL);
+	expr_yyerror_more(yyscanner, message, NULL);
 }
 
 /*
  * Called before any actual parsing is done
  */
-void
+yyscan_t
 expr_scanner_init(const char *str, const char *source,
-				  const int lineno, const char *line,
-				  const char *cmd, const int ecol)
+				  int lineno, const char *line,
+				  const char *cmd, int ecol)
 {
+	yyscan_t yyscanner;
 	Size	slen = strlen(str);
 
-	/* save context informations for error messages */
-	expr_source = (char *) source;
-	expr_lineno = (int) lineno;
-	expr_full_line = (char *) line;
-	expr_command = (char *) cmd;
-	expr_col = (int) ecol;
+	/* Set up yyscan_t */
+	yylex_init(&yyscanner);
+
+	/* save context information for error messages */
+	expr_source = source;
+	expr_lineno = lineno;
+	expr_full_line = line;
+	expr_command = cmd;
+	expr_col = ecol;
 
 	/* reset error pointers for this scan */
 	yycol = yyline = 0;
 
 	/*
-	 * Might be left over after error
-	 */
-	if (YY_CURRENT_BUFFER)
-		yy_delete_buffer(YY_CURRENT_BUFFER);
-
-	/*
 	 * Make a scan buffer with special termination needed by flex.
 	 */
-	scanbuflen = slen;
 	scanbuf = pg_malloc(slen + 2);
 	memcpy(scanbuf, str, slen);
 	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2, yyscanner);
 
-	BEGIN(INITIAL);
+	return yyscanner;
 }
 
 
 /*
- * Called after parsing is done to clean up after seg_scanner_init()
+ * Called after parsing is done to clean up after expr_scanner_init()
  */
 void
-expr_scanner_finish(void)
+expr_scanner_finish(yyscan_t yyscanner)
 {
-	yy_delete_buffer(scanbufhandle);
+	yy_delete_buffer(scanbufhandle, yyscanner);
 	pg_free(scanbuf);
+	yylex_destroy(yyscanner);
+
 	expr_source = NULL;
 	expr_lineno = 0;
 	expr_full_line = NULL;