Re: Add returns_nonnull to infallible allocators

On 06.07.26 20:11, Tristan Partin wrote:
> On Mon Jul 6, 2026 at 6:10 PM UTC, Tristan Partin wrote:
>> Postgres memory allocators, by default, ERROR out on memory allocation
>> failures. An ERROR leads to a longjmp, which means that the caller of
>> the allocator will never see a NULL return value. We can explicitly let
>> the compiler know about this behavior by adding the returns_nonnull
>> attribute to the allocators that follow this behavior. Postgres does
>> support _extended versions of some of the allocators that take a flaks
>> argument. The caller can provide the MCXT_ALLOC_NO_OOM flag to these
>> allocators to request that they return NULL on allocation failure
>> instead of ERROR-ing out. The _extended allocators cannot be marked as
>> returns_nonnull because of that.
>>
>> By using returns_nonnull, we can help the compiler to optimize call
>> sites.

Your patch marks palloc_mul_extended() as pg_attribute_returns_nonnull,
which seems incorrect per the above description.

Also, per the discussion in the counted_by thread, lets put these new
attributes in their more correct position in front of the declaration.
(Note that several of these already use pg_nodiscard, which is also an
attribute.) That way we can also use the MSVC annotation _Ret_notnull_.