We usually did this, but sometimes they were named after what they did,
rather than what they cleaned up.
There are still a few exceptions:
1. I didn't bother creating destroy_xxx wrappers for htable routines
which already existed.
2. Sometimes destructors really are used for side-effects (eg. to simply
mark that something was freed): these are clearer with boutique names.
3. Generally destructors are static, but they don't need to be: in some
cases we attach a destructor then remove it later, or only attach
to *some* cases. These are best with qualifiers in the destroy_<type>
name.
Suggested-by: @ZmnSCPxj
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Error code is inverted (which makes sense: who returns 'true' on
error?), and anyway there's a leak if we do error.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
`pay_index` has no valid value if not PAID anyway, so
we should correctly leave it uninitialized.
Analysis via valgrind will catch incorrect use of
uninitialized fields.
If we load it with a dummy 0 value, then an
incorrect use of `pay_index` whan invoice is not
PAID will not get caught by valgrind.
