X2WinRpcAdapter: remote Windows debugging over FlatBuffers RPC

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "vendor/flatbuffers"]
+	path = vendor/flatbuffers
+	url = https://github.com/google/flatbuffers.git

CMakeLists.txt

@@ -30,6 +30,32 @@ if (NOT BN_INTERNAL_BUILD)
 	message("CMAKE_PREFIX_PATH is: ${CMAKE_PREFIX_PATH}")
 endif()
 
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# FlatBuffers is used for the x2win RPC protocol. Its C++ runtime is header-only (see
+# FlatBuffers_Library_SRCS in vendor/flatbuffers/CMakeLists.txt -- every entry is a .h, no .cpp),
+# so unlike Protobuf/Abseil (formerly vendored here for the same protocol, since removed) there's
+# no compiled static lib whose CRT/ABI settings need to match whatever links against it -- only
+# flatc (the schema compiler) is an actual build-time binary. That's what let x2winstub drop its
+# MSVC-ABI-pinned toolchain requirement for MinGW-w64 once the protocol finished migrating over.
+# flatbuffers_generate_headers() (used by core/CMakeLists.txt and x2winstub/CMakeLists.txt) comes
+# from vendor/flatbuffers/CMake/BuildFlatBuffers.cmake, which flatbuffers' own CMakeLists.txt
+# already include()s, so no separate include() is needed here the way protobuf-generate.cmake was.
+set(FLATBUFFERS_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+set(FLATBUFFERS_INSTALL OFF CACHE BOOL "" FORCE)
+set(FLATBUFFERS_BUILD_FLATC ON CACHE BOOL "" FORCE)
+add_subdirectory(vendor/flatbuffers)
+
+# Generated once here and shared via target_link_libraries(... x2win_fbs) from both
+# core/CMakeLists.txt and x2winstub/CMakeLists.txt, rather than calling
+# flatbuffers_generate_headers() separately from each (which would define two CMake targets
+# both named "x2win_fbs" and fail to configure -- target names must be unique project-wide).
+flatbuffers_generate_headers(
+    TARGET x2win_fbs
+    SCHEMAS ${CMAKE_SOURCE_DIR}/protocol/x2win.fbs
+)
+
 add_subdirectory(core)
 add_subdirectory(api)
 
@@ -58,6 +84,7 @@ endif()
 # WinDbg installer CLI (standalone, spawned by debuggercore API)
 if(WIN32)
 	add_subdirectory(installer)
+	add_subdirectory(x2winstub)
 endif()
 
 # Documentation validation target

build.md

@@ -22,9 +22,14 @@ git checkout dev
 
 - Build the debugger
 
+  FlatBuffers (needed for `X2WinRpcAdapter`'s wire protocol) is vendored as a git submodule
+  under `vendor/` and built as part of this project's own CMake configure/build -- no separate
+  install step needed, just make sure submodules are cloned (`--recurse-submodules` below, or
+  `git submodule update --init --recursive` after the fact).
+
 ```bash
 # Get the source
-git clone https://github.com/Vector35/debugger.git
+git clone --recurse-submodules https://github.com/Vector35/debugger.git
 
 # Do an out-of-source build
 mkdir -p build

core/CMakeLists.txt

@@ -38,6 +38,8 @@ file(GLOB ADAPTER_SOURCES CONFIGURE_DEPENDS
 		adapters/esrevenadapter.h
 		adapters/lldbcoredumpadapter.cpp
 		adapters/lldbcoredumpadapter.h
+		adapters/x2winrpcadapter.cpp
+		adapters/x2winrpcadapter.h
 	)
 
 if(WIN32)
@@ -212,6 +214,26 @@ else()
 			)
 endif()
 
+# FlatBuffers for the x2win RPC protocol (protocol/x2win.fbs), generated once at the top-level
+# CMakeLists.txt and shared with x2winstub/CMakeLists.txt.
+#
+# Deliberately not target_link_libraries(debuggercore x2win_fbs): every other
+# target_link_libraries() call on debuggercore in this file uses the plain (no PUBLIC/PRIVATE)
+# signature, and CMake forbids mixing plain and keyword signatures for the same target anywhere
+# in the project -- so a PRIVATE-only x2win_fbs link isn't an option here. Plain/public would
+# instead propagate x2win_fbs's generated-header "source" to every downstream consumer of
+# debuggercore (ui, cli), which fails to configure because that generated file, from their
+# directory scope, isn't recognized as a build product (GENERATED doesn't propagate cross-directory
+# pre-CMake 3.20 semantics). Depending on the include dir + generation step directly sidesteps
+# target_link_libraries entirely, so it stays private to debuggercore without touching the
+# project's existing plain-signature convention.
+add_dependencies(debuggercore GENERATE_x2win_fbs)
+target_include_directories(debuggercore PRIVATE
+    ${CMAKE_BINARY_DIR}/x2win_fbs
+    ${CMAKE_SOURCE_DIR}/vendor/flatbuffers/include
+)
+
+
 if (WIN32)
 	add_custom_command(TARGET debuggercore PRE_LINK
 		COMMAND ${CMAKE_COMMAND} -E echo "Copying DbgEng DLLs"