BUG #14472: Backend crash​e​​s​ on array append for domains of array with constraint check

The following bug has been logged on the website:

Bug reference: 14472
Logged by: Marcos Castedo
Email address: marcos(dot)castedo(at)anachronics(dot)com
PostgreSQL version: 9.6.1
Operating system: Debian stretch
Description:

We have an issue related with bug #14414 reported on PostgreSQL 9.6.1.

Test case:

BEGIN;

CREATE OR REPLACE FUNCTION x_domain_test_check(integer[])
RETURNS boolean AS $$
BEGIN
RETURN true;
END;
$$ LANGUAGE plpgsql IMMUTABLE;

CREATE DOMAIN x_domain_test AS integer[]
CHECK(x_domain_test_check(value));

DO $$
DECLARE
v_test x_domain_test;
BEGIN
v_test := '{}'::x_domain_test;
v_test := v_test || 1; --SEGV on 9.6.1 with #14414 fixed
END;
$$;

ROLLBACK;

With 9.6.1 vanilla the test case fai​​l​s​ with SPI_connect error
(SPI_ERROR_CONNECT), but with ​the following patch applied (take​n​ from
#14414​'s​ fix on github) the backend crash​e​​s​ with "Segmentation
fault"​​.

--- postgresql-9.6.1/src/pl/plpgsql/src/pl_exec.c 2016-10-24
17:08:51.000000000 -0300
+++ postgresql-9.6.1-1/src/pl/plpgsql/src/pl_exec.c 2016-12-21
12:38:39.176980654 -0300
@@ -6102,6 +6102,8 @@ exec_cast_value(PLpgSQL_execstate *estat
ExprContext *econtext = estate->eval_econtext;
MemoryContext oldcontext;

+ SPI_push();
+
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

econtext->caseValue_datum = value;
@@ -6115,6 +6117,8 @@ exec_cast_value(PLpgSQL_execstate *estat
cast_entry->cast_in_use = false;

MemoryContextSwitchTo(oldcontext);
+
+ SPI_pop();
}
}