At the heart of BuildKit is LLB (Low-Level Build definition). Think of it as the LLVM IR of build systems. LLB is a binary protocol (protobuf) that describes a DAG of filesystem operations: run a command, copy files, mount a filesystem. It’s content-addressable, which means identical operations produce identical hashes, enabling aggressive caching.
This is not the only surprise in this article.
。关于这个话题，Line官方版本下载提供了深入分析
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if(h->ref--)return;