Suppress complaints about leaks in function cache loading.

PL/pgSQL and SQL-function parsing leak some stuff into the long-lived
function cache context.  This isn't really a huge practical problem,
since it's not a large amount of data and the cruft will be recovered
if we have to re-parse the function.  It's not clear that it's worth
working any harder than the previous patch did to eliminate these
leak complaints, so instead silence them with a suppression rule.

This suppression rule also hides the fact that CachedFunction structs
are intentionally leaked in some cases because we're unsure if any
fn_extra pointers remain.  That might be nice to do something about
eventually, but it's not clear how.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/285483.1746756246@sss.pgh.pa.us

src/tools/valgrind.supp

@@ -194,3 +194,24 @@
    Memcheck:Addr8
    fun:pg_numa_touch_mem_if_required
 }
+
+
+# Memory-leak suppressions
+# Note that a suppression rule will silence complaints about memory blocks
+# allocated in matching places, but it won't prevent "indirectly lost"
+# complaints about blocks that are only reachable via the suppressed blocks.
+
+# Suppress complaints about stuff leaked during function cache loading.
+# Both the PL/pgSQL and SQL-function parsing processes generate some cruft
+# within the function's cache context, which doesn't seem worth the trouble
+# to get rid of.  Moreover, there are cases where CachedFunction structs
+# are intentionally leaked because we're unsure if any fn_extra pointers
+# remain.
+{
+   hide_function_cache_leaks
+   Memcheck:Leak
+   match-leak-kinds: definite,possible,indirect
+
+   ...
+   fun:cached_function_compile
+}