Why does rebuilding programs with `cargo build-bpf` take so long in a workspace?

Question

Compared to the normal cargo build --release --workspace, rebuilding a program with cargo build-bpf (or sbf) ends up redoing quite a bit of work. If you have already built the workspace using cargo build, it caches that result and doesn't try to rebuild if nothing has changed.

Is there a reason cargo build-bpf doesn't have this same behavior? It appears to build each package in the workspace individually. Is there a reason for this? Is there a path forward that builds all the programs together like normal cargo builds instead of one at a time?

Answer 1

In normal cases, the build artifacts are cached, like with normal cargo.

For example, if you try to build the SPL token program at https://github.com/solana-labs/solana-program-library/tree/master/token/program twice, on the second round you'll see:

$ cargo build-sbf
    Finished release [optimized] target(s) in 0.24s

It could be that your program's transitive dependencies have different features enabled on the same crate, which forces multiple compilations of the same crate, which need to be recompiled on every subsequent build. This is a known "feature" of cargo, however.

Edit: sorry, I missed the "workspace" part of this. This is a bug with cargo build-sbf