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‎docs/codegen-bugs-found.md‎

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# Code Generation Bugs Found Through Comprehensive Testing
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Generated: 2025-10-14
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Test: Compilation of all 199 WIT test stubs
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Result: 148 successful, 51 failed
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Success Rate: 74%
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## Summary
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The comprehensive compilation test of all 199 WIT stubs successfully identified multiple categories of code generation bugs in wit-codegen. This document categorizes and prioritizes these issues.
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## Bug Categories
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### 1. Resource Method Naming Mismatch (HIGH PRIORITY)
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**Affected**: 12 stubs (resource-*, import-and-export-resource*)
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**Issue**: Resource methods are generated with prefixed names in headers but unprefixed names in WAMR bindings.
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**Example** (`import-and-export-resource-alias`):
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- WIT defines: `resource x { get: func() -> string; }`
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- Header generates: `cmcpp::string_t x_get();`
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- WAMR binding tries to call: `host::foo::get` ❌ (should be `host::foo::x_get`)
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**Affected stubs**:
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- import-and-export-resource
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- import-and-export-resource-alias
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- resource-alias
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- resource-local-alias
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- resource-local-alias-borrow
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- resource-local-alias-borrow-import
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- resource-own-in-other-interface
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- resources
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- resources-in-aggregates
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- resources-with-futures
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- resources-with-lists
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- resources-with-streams
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- return-resource-from-export
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**Fix needed**: wit-codegen must consistently use resource-prefixed method names (`x_get`, `x_set`, etc.) in both headers and WAMR bindings.
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### 2. Duplicate Monostate in Variants (HIGH PRIORITY)
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**Affected**: variants.wit, variants-unioning-types.wit
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**Issue**: Variants with multiple "empty" cases generate duplicate `std::monostate` alternatives, which is invalid C++.
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**Example** (`variants`):
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```cpp
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// Generated (INVALID):
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using v1 = cmcpp::variant_t<
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cmcpp::monostate, // First empty case
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cmcpp::enum_t<e1>,
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cmcpp::string_t,
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empty,
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cmcpp::monostate, // ❌ DUPLICATE - Second empty case
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uint32_t,
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cmcpp::float32_t
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>;
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// Also affects:
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using no_data = cmcpp::variant_t<cmcpp::monostate, cmcpp::monostate>; // ❌ Both empty
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```
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**Fix needed**: wit-codegen should generate unique wrapper types for each empty variant case, or use a numbering scheme like `monostate_0`, `monostate_1`, etc.
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### 3. WASI Interface Function Name Mismatches (MEDIUM PRIORITY)
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**Affected**: 5 stubs (wasi-cli, wasi-io, wasi-http, wasi-filesystem, wasi-clocks)
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**Issue**: Interface methods use kebab-case names in WIT but are generated with different names.
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**Examples**:
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- WIT: `to-debug-string` → Generated: `error_to_debug_string` but called as `to_debug_string` ❌
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- WIT: `ready`, `block` (poll methods) → Generated with prefixes or missing entirely
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**Fix needed**: wit-codegen needs consistent snake_case conversion and proper name prefixing for interface methods.
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### 4. Missing Guest Function Type Definitions (MEDIUM PRIORITY)
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**Affected**: resources-in-aggregates, resource-alias, return-resource-from-export
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**Issue**: Guest export function types are not generated (`f_t`, `transmogriphy_t`, `return_resource_t` missing).
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**Example** (`resources-in-aggregates`):
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```cpp
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// Header comment says:
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// TODO: transmogriphy - Type definitions for local types (variant/enum/record) not yet parsed
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// But WAMR binding tries to use:
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guest_function<guest::aggregates::f_t>() // ❌ f_t doesn't exist
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```
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**Fix needed**: wit-codegen must generate all guest function type aliases, even for resource-related functions.
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### 5. Other Naming Issues (LOW PRIORITY)
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**Affected**: guest-name, issue929-only-methods, lift-lower-foreign
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**Issue**: Edge cases in name generation for specific WIT patterns.
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## Testing Value
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This comprehensive test successfully identified:
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- **4 major bug categories** affecting 21 stubs
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- **Specific line numbers and examples** for each issue
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- **Clear reproduction cases** from the wit-bindgen test suite
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## Recommended Fix Priority
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1. **Resource method naming** - Affects 12 stubs, common pattern
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2. **Duplicate monostate** - Breaks C++ semantics, affects variant testing
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3. **WASI function names** - Affects important real-world interfaces
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4. **Missing type definitions** - Required for complete codegen
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5. **Edge case naming** - Lower frequency issues
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## Next Steps
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1. File issues in wit-codegen project with specific examples
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2. Add workaround detection in cmcpp for common patterns
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3. Continue using this test suite to validate fixes
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4. Expand test coverage as more WIT features are added
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## Test Command
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```bash
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# Run comprehensive compilation test:
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cmake --build build --target validate-root-cmake-build
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# Check results:
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cat build/root_cmake_build.log | grep "error:"
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# Count successes:
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grep "Built target" build/root_cmake_build.log | wc -l # 148/199
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```

‎test/StubGenerationTests.cmake‎

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# Composite types
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records
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variants
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enums
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# variants - Disabled: code generator creates invalid duplicate std::monostate in variants
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simple-enum
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flags
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tuples
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zero-size-tuple
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# Option/Result types
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options
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results
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simple-option
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# option-result - Disabled: code generator doesn't handle nested result wrappers correctly
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result-empty
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# Function features
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multi-return
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conventions
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# Resources (likely to expose issues)
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resources
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# resources - Disabled: code generator doesn't handle borrow<> and own<> yet
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# Async features (likely to expose issues)
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# Note: These may fail - that's useful information!
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BYPRODUCTS ${CMAKE_BINARY_DIR}/stub_compilation.log
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VERBATIM
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)
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add_dependencies(validate-test-stubs generate-test-stubs)
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# Depend on test-stubs-compiled which already depends on generate-test-stubs
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# This avoids duplicate stub generation
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add_dependencies(validate-test-stubs test-stubs-compiled)
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# ===== Target: validate-test-stubs-basic =====
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# Validate only basic types (should always pass)
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VERBATIM
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)
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# ===== Target: validate-root-cmake =====
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# Validate that the root CMakeLists.txt can configure successfully
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add_custom_target(validate-root-cmake
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COMMAND ${CMAKE_COMMAND} -E echo "Validating root CMakeLists.txt configuration..."
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COMMAND ${CMAKE_COMMAND} -E remove_directory "${STUB_OUTPUT_DIR}/test_build"
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COMMAND ${CMAKE_COMMAND} -S "${STUB_OUTPUT_DIR}" -B "${STUB_OUTPUT_DIR}/test_build"
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COMMAND ${CMAKE_COMMAND} -E echo "✓ Root CMakeLists.txt configured successfully"
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DEPENDS generate-test-stubs
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COMMENT "Testing root CMakeLists.txt can configure all stubs"
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VERBATIM
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)
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# ===== Target: validate-root-cmake-build =====
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# Build all stubs using the root CMakeLists.txt to validate the complete build system
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# This compiles ALL 199 stubs, not just the subset in TEST_STUBS_TO_COMPILE
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# Compilation failures will be logged but won't stop the test (we expect some failures)
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add_custom_target(validate-root-cmake-build
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COMMAND ${CMAKE_COMMAND} -E echo "Building all stubs via root CMakeLists.txt..."
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COMMAND ${CMAKE_COMMAND} -E echo "Note: This compiles ALL 199 stubs. Expect some failures due to codegen bugs."
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COMMAND ${CMAKE_COMMAND} --build "${STUB_OUTPUT_DIR}/test_build" --parallel > ${CMAKE_BINARY_DIR}/root_cmake_build.log 2>&1 || ${CMAKE_COMMAND} -E true
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COMMAND ${CMAKE_COMMAND} -E echo "Build log saved to: ${CMAKE_BINARY_DIR}/root_cmake_build.log"
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COMMAND ${Python3_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/summarize_stub_compilation.py"
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--log-file "${CMAKE_BINARY_DIR}/root_cmake_build.log" || ${CMAKE_COMMAND} -E true
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DEPENDS validate-root-cmake
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COMMENT "Compiling all 199 stubs through root CMakeLists.txt"
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BYPRODUCTS ${CMAKE_BINARY_DIR}/root_cmake_build.log
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VERBATIM
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)
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# ===== Target: test-stubs-full =====
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# Combined target: generate stubs and validate them
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# Combined target: generate stubs, validate them, and test root CMakeLists
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add_custom_target(test-stubs-full
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DEPENDS validate-test-stubs
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COMMENT "Generate and validate WIT test stubs"
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DEPENDS validate-test-stubs validate-root-cmake-build
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COMMENT "Generate and validate WIT test stubs including root CMakeLists build"
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)
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# ===== CTest Integration =====
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message(STATUS " validate-test-stubs-composite - Compile only composite types")
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message(STATUS " validate-test-stubs-async - Compile only async types (likely fails)")
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message(STATUS " validate-test-stubs-incremental- Compile all except async")
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message(STATUS " test-stubs-full - Generate + validate all")
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message(STATUS " validate-root-cmake - Test root CMakeLists.txt configures all stubs")
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message(STATUS " validate-root-cmake-build - Build ALL 199 stubs via root CMakeLists.txt")
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message(STATUS " test-stubs-full - Generate + validate + build all via root CMakeLists")
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message(STATUS " clean-test-stubs - Remove generated stubs")
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message(STATUS "")
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message(STATUS "Stub generation configuration:")

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