age_to*list functions crash the server (SIGSEGV) on array-shaped SQL literals

[hkjiang26]

AGE Version: apache/age master @ cfd3b63 (2026-08-14), extension 1.8.0, on PostgreSQL 18.6

Installation Method: Docker

API: SQL (psql)

Steps to reproduce

1. On a fresh database, run (no data required):

LOAD 'age';
SET search_path = ag_catalog, public;
SELECT ag_catalog.age_tobooleanlist('[true]');

All four age_to*list functions crash deterministically on array-shaped literal arguments (12 shapes verified):

Statement	Result
age_tobooleanlist('[true]'), ('[null]'), ('[true, null, false]')	SIGSEGV
age_tofloatlist('[true]'), ('[1]'), ('[null]')	SIGSEGV
age_tointegerlist('[true]'), ('[null]')	SIGSEGV
age_tostringlist('[true]'), ('[null]'), ('[1, null, "a"]')	SIGSEGV

Other array shapes ('[1]', '["a"]', '[1.5]' for the mismatched functions) give a bogus ERROR: toBooleanList() argument must resolve to a list or null instead — same root cause, non-crashing bit pattern.

Expected behavior

The Cypher equivalents work correctly and define the expected behavior:

SELECT * FROM cypher('g', $$ RETURN toBooleanList([true]) $$) AS (r agtype);
-- r = [true]

The SQL form should either return the same result or raise a clean error; it must never crash the backend.

Actual behavior

psql: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
psql: error: connection to server was lost

Server log (docker logs):

LOG:  client backend (PID 14030) was terminated by signal 11: Segmentation fault
LOG:  all server processes terminated; reinitializing

Root cause (in src/backend/utils/adt/agtype.c): type confusion at the SQL boundary. For VARIADIC "any" functions, PostgreSQL resolves an unknown-type literal to text (verified with the same-signature builtin json_build_array('[true]') → ["[true]"]), i.e. the function receives a text[] (ArrayType) datum, not agtype. The C functions read the argument with AG_GET_ARG_AGTYPE_P(0) without ever checking get_fn_expr_argtype(), so the text[] datum is reinterpreted as an agtype container. Depending on the literal's byte pattern the garbage either passes the AGT_ROOT_IS_ARRAY root check and crashes while iterating elements (the 12 shapes above), or fails it and produces the bogus argument must resolve to a list or null error ('[1]', '["a"]', '[1.5]'). Passing an explicit ::agtype cast works correctly — age_tobooleanlist('[true]'::agtype) returns [true] — and the explicit VARIADIC ARRAY[...] form hits the same reinterpretation. EXPLAIN (VERBOSE) of a crashing call also crashes the backend.

Cypher is safe: literal lists are built through agtype_build_list (null elements get real value slots) and the transform passes a typed agtype expression, so the C code never sees a text[]; the PREPARE/EXECUTE parameter path was verified safe as well. Trigger surface = AGE's public SQL API (shared-instance DoS, same class as the ? crash).