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Expose a stable native API for class and property access - #789
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t-kalinowski wants to merge 5 commits into
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t-kalinowski wants to merge 5 commits into
t-kalinowski wants to merge 5 commits into
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Register S7_get_class and S7_get_prop for native consumers, with a public C/C++ header and documented signatures for other bindings. Reuse S7's class lookup and property getters so consumers do not depend on storage details. Add compiled consumer tests and document the API contract. Closes #788
Provide shared function pointers initialized once by S7_init_api() in the consumer's DLL initialization routine. Register the existing accessors directly and remove the forwarding wrappers and per-call name validation. Document scalar, non-missing property names as a caller precondition. Update the compiled consumer tests to initialize the API once and use it from both C and C++.
Compare class lookup, stored properties, and a custom getter through the native API and through cached R calls evaluated from C. Batch 1000 accesses per timing sample, verify returned values, and save timings and build metadata for comparisons across fresh R sessions.
t-kalinowski
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October 20, 2026 18:23
hadley
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Oct 21, 2026
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I don't really have any strong feelings here, but I added a few questions as they occurred to me
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| #' S7 provides a stable native API for retrieving class definitions and reading | ||
| #' properties without depending on how S7 stores them. |
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| #' S7 provides a stable native API for retrieving class definitions and reading | |
| #' properties without depending on how S7 stores them. | |
| #' S7 provides a stable native API for retrieving class definitions and reading | |
| #' properties. |
| #' S7 provides a stable native API for retrieving class definitions and reading | ||
| #' properties without depending on how S7 stores them. | ||
| #' | ||
| #' * `SEXP S7_get_class(SEXP object)` returns the stored S7 class definition, or |
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get_class() or class_get()? Is one or the other more C like?
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| #' static SEXP object_value(SEXP object) { | ||
| #' SEXP name = PROTECT(Rf_mkString("value")); | ||
| #' SEXP value = S7_get_prop(object, name); | ||
| #' UNPROTECT(1); | ||
| #' return value; | ||
| #' } |
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Would it make the example clearer to put this in a separate file, like you would typically?
| local_dev_S7_lib(frame = frame) | ||
| if (is.null(lib)) { | ||
| dir.create(lib <<- tempfile("S7-native-api-")) | ||
| install.packages( |
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Does this make the tests substantially slower?
| local_native_api <- local({ | ||
| lib <- NULL | ||
| function(frame = parent.frame()) { | ||
| local_dev_S7_lib(frame = frame) |
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Native extensions currently need to depend on S7's internal representation or call back into R to inspect objects. This adds a stable native API for retrieving S7 class definitions and reading properties through their getters.
S7_get_class()returns the stored S7 class definition, resolving shared class references, orR_NilValuewhen there is none.S7_get_prop()reads a property with the same getter and storage behavior asprop(). A non-missing scalar character name is a caller precondition.S7-init.hin their initialization source file, callS7_init_api()during DLL initialization, and includeS7.helsewhere. Calls use shared function pointers without per-call initialization checks.R_GetCCallable().The registered entry points use the existing C implementations directly. Documentation describes the two function contracts and includes a complete example of initialization and property access. A compiled consumer fixture exercises C, C++, direct registered lookup, and repeated header inclusion. The benchmark compares native access with evaluating cached and namespace-qualified R calls.
Local results from bench/native-api.R, using R 4.6.1 on an Apple M4 Max with clang
-O2:Rf_eval()Times are per access: the median of session medians from three fresh R sessions, with 1,000 accesses per C loop. R functions and complete call objects are cached before timing, and all paths repeatedly access the same object. Parsing and call construction are excluded.
Evaluating a namespace-qualified
S7::prop()call takes 0.32 µs for a stored property versus 0.063 µs through the native API (5.1x faster). Getters still execute R code. Class lookup also avoids the general classification logic in R'sS7_class().Closes #788.