When code depends on environment/build features (SIMD/FP16 availability, OpenCV versioned APIs, packing layout support, OS/ABI-specific macros), you must (1) gate the code at compile time with the correct macros and (2) reflect the real capability in the backend’s `support_*` flags so the framework won’t select an unsupported execution path. Apply this as a standard checklist: - Optional dependencies: wrap includes/usages in the correct version guards (e.g., `CV_MAJOR_VERSION`/`CV_MINOR_VERSION`). - SIMD/FP16 paths: guard the *whole* implementation and call sites with the precise feature expression (e.g., NEON + the required FP mode), not only `__ARM_NEON`. - Backend packing/layout: if a packing layout or axis is not implemented, disable it in `create_pipeline()` (e.g., set `support_packing = false` or the equivalent packing flags), and then you can remove/avoid unused unpacking glue. - OS/arch macros: prefer correct architecture detection macros for each platform target (e.g., consider `_WIN32` when detecting x64). Example patterns: ```cpp // 1) Version-gated optional headers #if (CV_MAJOR_VERSION >= 3) #include #endif // 2) SIMD/FP16 gated implementation #if defined(__ARM_NEON) && (__ARM_FP & 2) static int lstm_fp16(...){ /* fp16 NEON path */ } #endif // 3) Capability flags match implementation int InnerProduct_arm::create_pipeline(const Option& opt) { if (axis == 1) support_packing = false; // packing/layout not implemented for this axis return 0; } // 4) If you disable packing support, don’t keep unpacking logic around if (!support_vulkan_packing && !support_vulkan_any_packing) { // avoid selecting unpack/convert glue; only accept supported layouts } ``` This prevents build-breaks on unsupported platforms, avoids dead/incorrect code paths, and ensures runtime execution matches what the backend actually supports.