Re: jsonapi: scary new warnings with LTO enabled

> On 17 Apr 2025, at 00:12, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Daniel Gustafsson <daniel(at)yesql(dot)se> writes:
>>> On 16 Apr 2025, at 23:42, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> I'm not sure
>>> how other than giving up on stack allocation of JsonLexContexts,
>>> though, especially if we consider the jsonapi API frozen. But seeing
>>> that there are only three such call sites and none of them seem in the
>>> least performance-critical, maybe we should just do that?
>
>> I can't see any other option really, and there is no performance angle really
>> so that should be safe. Since I committed at least one of these, let me know
>> if you want me to tackle it.
>
> The only alternative I can see that might stop the warning is if we
> can find a way to make it clearer to the optimizer that the FREE()
> isn't reached. But I'm not sure about a trustworthy way to make that
> happen. Maybe it'd work to change the signature of freeJsonLexContext
> (or perhaps better, add a separate entry point) so that the caller is
> passing a bool constant that controls whether to free the struct.
> We could have an Assert that compares that to the state of the
> JSONLEX_FREE_STRUCT flag to catch mistakes. This seems kind of messy
> though.

Yeah, that seems messy enough that someone down the line will go "why on earth"
and we'll have to revisit this discussion. It can probably be made to work but
I doubt it will be worth it compared to allocating on the heap.

--
Daniel Gustafsson