Consider adding a bpf-entrypoint feature to enable the entrypoint

[joncinque]

Problem

As noted at https://github.com/paladin-bladesmith/sol-stake-view-program/pull/5/files#r1699203567, there are some competing ways of defining certain program features and then using them.

In this case, some programs specify a bpf-entrypoint feature, which enables the entrypoint for program builds. Historically, programs have used the no-entrypoint feature to disable the entrypoint, which is an antipattern for crate features, which should typically add functionality rather than remove.

Proposed Solution

Come up with a standard and use it here!

cc @febo @buffalojoec

[buffalojoec]

I think the additive bpf-entrypoint feature is probably a good standard. Optionally we could try to pack a few things into platform tools, like automatically detecting this feature when building with cargo build-sbf and/or allowing some custom crate type (ie. crate-type = ["sbf"]) that could abstract some of the entrypoint boilerplate.

I also think we should consider renaming the feature to sbf-entrypoint. 😅

[lorisleiva]

Hey guys, am I right to say this would be for Solana 2.0+? If so, we already have that information when we generate the template so we can add that flag for Solana 2.0+ only. Wdyt?

[joncinque]

There's nothing specific to Solana v2, it's whether we want to create a new convention that will make it easier to share program crates. With that said, this might not be such a big issue when we start generating and publishing client crates.