Borrow deferred containers instead of copying them - #167
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json_compiler stored each deferred named child by value, so a container nested d levels deep was copied d times over: compile_container() recursed into the copy and deferred its children the same way. On a memory-constrained target that dominated the cost of a compile - it was most of why one needed roughly 16x the source JSON in heap. The source document outlives the whole compile. It is the caller's json, reached by reference through compile() -> compile_container() -> handle_container_metadata(), so a pointer is safe and the copy was never serving a purpose. Measured on an ESP32-S3 across a range of story sizes, peak heap fell from 16.4x the source size to 12.05x. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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json_compilerstored each deferred named child by value (std::tuple<json, std::string>), so a container nested d levels deep was copied d times over:compile_container()recursed into the copy and deferred its children the same way.The source document outlives the whole compile — it is the caller's
json, reached by reference throughcompile()→compile_container()→handle_container_metadata()— so a pointer is safe and the copy was never serving a purpose.Measured
On an ESP32-S3, peak heap for a compile fell from 16.4x the source JSON's size to 12.05x. On a memory-constrained target that was most of what made compiling on-device impractical; it matters less on a desktop, but it is pure overhead everywhere.
ctestpasses and 77 real stories compile to byte-identical output.