From ff88db91036fed10dedb9e38786506d0460bd7dd 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 c0825ae6790..8b2e61d27e0 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -3889,8 +3889,14 @@ 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;
@@ -3909,11 +3915,7 @@ 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 f9690c64957..28b23cdc678 100644
--- a/src/bin/pgbench/t/001_pgbench_with_server.pl
+++ b/src/bin/pgbench/t/001_pgbench_with_server.pl
@@ -633,6 +633,56 @@ SELECT :v0, :v1, :v2, :v3;
 }
 	});
 
+# test nested \if constructs
+$node->pgbench(
+	'--no-vacuum --client=1 --transactions=1',
+	0,
+	[qr{actually processed}],
+	[qr{^$}],
+	'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);'