Re: Add returns_nonnull to infallible allocators

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.

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--
Tristan Partin
PostgreSQL Contributors Team
AWS (https://aws.amazon.com)