From ff9dc96f370aa33a5c1c578c43c598473705d82f Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 15 Dec 2024 14:14:15 -0500
Subject: [PATCH] pgbench: fix misprocessing of some nested \if constructs.

An \if command appearing within a false (not-to-be-executed) \if
branch was incorrectly treated the same as \elif.  This could allow
statements within the inner \if to be executed when they should
not be.  Also the missing inner \if stack entry would result in an
assertion failure (in assert-enabled builds) when the final \endif
is reached.

Report and patch by Michail Nikolaev.  Back-patch to all
supported branches.

Discussion: https://postgr.es/m/CANtu0oiA1ke=SP6tauhNqkUdv5QFsJtS1p=aOOf_iU+EhyKkjQ@mail.gmail.com
---
 src/bin/pgbench/pgbench.c                    | 16 ++++---
 src/bin/pgbench/t/001_pgbench_with_server.pl | 50 ++++++++++++++++++++
 2 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index 47467c32dd8..36282a99bb6 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -3879,8 +3879,14 @@ advanceConnectionState(TState *thread, CState *st, StatsData *agg)
 						switch (conditional_stack_peek(st->cstack))
 						{
 							case IFSTATE_FALSE:
-								if (command->meta == META_IF ||
-									command->meta == META_ELIF)
+								if (command->meta == META_IF)
+								{
+									/* nested if in skipped branch - ignore */
+									conditional_stack_push(st->cstack,
+														   IFSTATE_IGNORED);
+									st->command++;
+								}
+								else if (command->meta == META_ELIF)
 								{
 									/* we must evaluate the condition */
 									st->state = CSTATE_START_COMMAND;
@@ -3899,11 +3905,7 @@ advanceConnectionState(TState *thread, CState *st, StatsData *agg)
 									conditional_stack_pop(st->cstack);
 									if (conditional_active(st->cstack))
 										st->state = CSTATE_START_COMMAND;
-
-									/*
-									 * else state remains in
-									 * CSTATE_SKIP_COMMAND
-									 */
+									/* else state remains CSTATE_SKIP_COMMAND */
 									st->command++;
 								}
 								break;
diff --git a/src/bin/pgbench/t/001_pgbench_with_server.pl b/src/bin/pgbench/t/001_pgbench_with_server.pl
index 956e290f3ef..65ffa4468f3 100644
--- a/src/bin/pgbench/t/001_pgbench_with_server.pl
+++ b/src/bin/pgbench/t/001_pgbench_with_server.pl
@@ -668,6 +668,56 @@ SELECT :v0, :v1, :v2, :v3;
 }
 	});
 
+# test nested \if constructs
+$node->pgbench(
+	'--no-vacuum --client=1 --exit-on-abort --transactions=1',
+	0,
+	[qr{actually processed}],
+	[qr{^$}],
+	'nested ifs',
+	{
+		'pgbench_nested_if' => q(
+			\if false
+				SELECT 1 / 0;
+				\if true
+					SELECT 1 / 0;
+				\elif true
+					SELECT 1 / 0;
+				\else
+					SELECT 1 / 0;
+				\endif
+				SELECT 1 / 0;
+			\elif false
+				\if true
+					SELECT 1 / 0;
+				\elif true
+					SELECT 1 / 0;
+				\else
+					SELECT 1 / 0;
+				\endif
+			\else
+				\if false
+					SELECT 1 / 0;
+				\elif false
+					SELECT 1 / 0;
+				\else
+					SELECT 'correct';
+				\endif
+			\endif
+			\if true
+				SELECT 'correct';
+			\else
+				\if true
+					SELECT 1 / 0;
+				\elif true
+					SELECT 1 / 0;
+				\else
+					SELECT 1 / 0;
+				\endif
+			\endif
+		)
+	});
+
 # random determinism when seeded
 $node->safe_psql('postgres',
 	'CREATE UNLOGGED TABLE seeded_random(seed INT8 NOT NULL, rand TEXT NOT NULL, val INTEGER NOT NULL);'