Date: Sun, 5 Apr 2020 19:54:19 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org,
	Robert Haas <robertmhaas@gmail.com>
Subject: Re: CLOBBER_CACHE_ALWAYS regression instability
Message-ID: <20200405235419.GA24134@alvherre.pgsql>
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On 2020-Apr-05, Tom Lane wrote:

> What I wish we had was alloca(), so you don't need a FUNC_MAX_ARGS-sized
> array to parse a two-argument function call.  Too bad C99 didn't add
> that.  (But some sniffing around suggests that an awful lot of systems
> have it anyway ... even MSVC.  Hmmm.)

Isn't it the case that you can create an inner block with a constant
whose size is determined by a containing block's variable?  I mean as in
the attached, which refuses to compile because of our -Werror=vla -- but
if I remove it, it compiles fine and works in my system.


-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9c3b6ad916..415ea17c68 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -103,7 +103,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	Node	   *first_arg = NULL;
 	int			nargs;
 	int			nargsplusdefs;
-	Oid			actual_arg_types[FUNC_MAX_ARGS];
 	Oid		   *declared_arg_types;
 	List	   *argnames;
 	List	   *argdefaults;
@@ -115,6 +114,9 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	char		aggkind = 0;
 	ParseCallbackState pcbstate;
 
+	{
+		Oid		actual_arg_types[list_length(fargs)];
+
 	/*
 	 * If there's an aggregate filter, transform it using transformWhereClause
 	 */
@@ -888,6 +890,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	/* if it returns a set, remember it for error checks at higher levels */
 	if (retset)
 		pstate->p_last_srf = retval;
+	}
 
 	return retval;
 }

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