Reland "[lldb][RPC] Upstream lldb-rpc-gen tool" (#146969)" Attempt 2 (#148996)

Second attempt at relanding the lldb-rpc-gen tool. This should fix 2
issues:

- An assert that was hitting when building on Linux. The assert would
hit in the server source emitter, specifically when attemping to
determine the storage size for a return type is that is a pointer, but
isn't a const char *, const char ** or void pointer.

The assert would hit when attempting to generate
SBAttachInfo::GetProcessPluginName, which returns a const char *
(meaning it shouldn't have been in the code block for the assert at
all). The reason that it was hitting the assert when generating this
function is that lldb_rpc_gen::TypeIsConstCharPtr was returning false
for this function even though it did return a const char *. This was
happening because when checking the return type for a const char *,
TypeIsConstCharPtr would only check that the underlying type was a
signed char. This failed on Linux (but was fine on Darwin), as the
underlying type also needs to be checked for being an unsigned char.

- Cross compiling support

The build for lldb-rpc-gen had no support for cross compiling and as
such, the sources generated for lldb-rpc-gen would get compiled too
early in phase 2 when cross compiling, before the Clang toolchain was
built and this led to an error when trying to include stdlib files. This
reland splits this build into 2 by building the tool first and then
compiling the sources in the second stage of the cross-compiled build.

Original PR Description:
This commit upstreams the lldb-rpc-gen tool, a ClangTool that generates
the LLDB RPC client and server interfaces. This tool, as well as LLDB
RPC itself is built by default. If it needs to be disabled, put
-DLLDB_BUILD_LLDBRPC=OFF in your CMake invocation.

https://discourse.llvm.org/t/rfc-upstreaming-lldb-rpc/85804

Original PR Link:
github.com/llvm/llvm-project/pull/138031

Author: chelcassanova

lldb/cmake/modules/LLDBConfig.cmake

@@ -323,4 +323,23 @@ else()
     set(LLDB_CAN_USE_DEBUGSERVER OFF)
 endif()
 
+# In a cross-compile build, we need to skip building the generated
+# lldb-rpc sources in the first phase of host build so that they can
+# get built using the just-built Clang toolchain in the second phase.
+if (NOT DEFINED LLDB_CAN_USE_LLDB_RPC_SERVER)
+  if ((CMAKE_CROSSCOMPILING OR LLVM_HOST_TRIPLE MATCHES "${LLVM_DEFAULT_TARGET_TRIPLE}") AND
+      CMAKE_SYSTEM_NAME MATCHES "AIX|Android|Darwin|FreeBSD|Linux|NetBSD|OpenBSD|Windows")
+    set(LLDB_CAN_USE_LLDB_RPC_SERVER ON)
+  else()
+    set(LLDB_CAN_USE_LLDB_RPC_SERVER OFF)
+  endif()
+endif()
+
+if (CMAKE_CROSSCOMPILING)
+  set(LLDB_BUILD_LLDBRPC OFF CACHE BOOL "")
+  get_host_tool_path(lldb-rpc-gen LLDB_RPC_GEN_EXE lldb_rpc_gen_exe lldb_rpc_gen_target)
+else()
+  set(LLDB_BUILD_LLDBRPC ON CACHE BOOL "")
+endif()
+
 include(LLDBGenerateConfig)

lldb/test/CMakeLists.txt

@@ -132,6 +132,10 @@ if(TARGET lldb-framework)
   add_lldb_test_dependency(lldb-framework)
 endif()
 
+if (LLDB_CAN_USE_LLDB_RPC_SERVER)
+  add_lldb_test_dependency(lldb-rpc-generate-sources)
+endif()
+
 # Add dependencies that are not exported targets when building standalone.
 if(NOT LLDB_BUILT_STANDALONE)
   add_lldb_test_dependency(
@@ -249,7 +253,8 @@ llvm_canonicalize_cmake_booleans(
   LLDB_TEST_SHELL_DISABLE_REMOTE
   LLDB_TOOL_LLDB_SERVER_BUILD
   LLDB_USE_SYSTEM_DEBUGSERVER
-  LLDB_IS_64_BITS)
+  LLDB_IS_64_BITS
+  LLDB_BUILD_LLDBRPC)
 
 # Configure the individual test suites.
 add_subdirectory(API)

lldb/test/Shell/RPC/Generator/Inputs/SBDummy.h

@@ -0,0 +1,9 @@
+RUN: %lldb-rpc-gen --output-dir=%t %S/../Inputs/SBDummy.h
+
+RUN: ls %t | FileCheck %s
+
+# We're just making sure that the tool emits the class names,
+# methods and skipped methods file in the output directory.
+CHECK: SBAPI.def
+CHECK: SBClasses.def
+CHECK: SkippedMethods.txt

lldb/test/Shell/RPC/Generator/Tests/CheckRPCGenToolByproducts.test

@@ -0,0 +1,3 @@
+# All tests for the tool need lldb-rpc-gen to be built.
+if not config.lldb_has_lldbrpc:
+   config.unsupported = True

lldb/test/Shell/RPC/Generator/lit.local.cfg

@@ -156,6 +156,16 @@ def use_lldb_substitutions(config):
             extra_args=["platform"],
             unresolved="ignore",
         ),
+        ToolSubst(
+            "%lldb-rpc-gen",
+            command=FindTool("lldb-rpc-gen"),
+            # We need the LLDB build directory root to pass into the tool, not the test build root.
+            extra_args=[
+                "-p " + config.lldb_build_directory + "/..",
+                '--extra-arg="-resource-dir=' + config.clang_resource_dir + '"',
+            ],
+            unresolved="ignore",
+        ),
         "lldb-test",
         "lldb-dap",
         ToolSubst(

lldb/test/Shell/helper/toolchain.py

@@ -33,6 +33,7 @@ config.lldb_build_directory = "@LLDB_TEST_BUILD_DIRECTORY@"
 config.have_lldb_server = @LLDB_TOOL_LLDB_SERVER_BUILD@
 config.lldb_system_debugserver = @LLDB_USE_SYSTEM_DEBUGSERVER@
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
+config.lldb_has_lldbrpc = @LLDB_BUILD_LLDBRPC@
 # The shell tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-shell")
 config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-shell")

lldb/test/Shell/lit.site.cfg.py.in

@@ -10,6 +10,12 @@ add_subdirectory(lldb-fuzzer EXCLUDE_FROM_ALL)
 
 add_lldb_tool_subdirectory(lldb-instr)
 add_lldb_tool_subdirectory(lldb-dap)
+if (LLDB_BUILD_LLDBRPC)
+  add_lldb_tool_subdirectory(lldb-rpc-gen)
+endif()
+if (LLDB_CAN_USE_LLDB_RPC_SERVER)
+  add_subdirectory(lldb-rpc)
+endif()
 
 if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
   add_lldb_tool_subdirectory(darwin-debug)

lldb/tools/CMakeLists.txt

@@ -0,0 +1,23 @@
+add_lldb_tool(lldb-rpc-gen
+    RPCCommon.cpp
+    server/RPCServerHeaderEmitter.cpp
+    server/RPCServerSourceEmitter.cpp
+    lldb-rpc-gen.cpp
+
+    CLANG_LIBS
+      clangAST
+      clangBasic
+      clangCodeGen
+      clangFrontend
+      clangLex
+      clangRewrite
+      clangSerialization
+      clangTooling
+
+    LINK_COMPONENTS
+      Support
+  )
+
+if (NOT DEFINED LLDB_RPC_GEN_EXE)
+  set(LLDB_RPC_GEN_EXE $<TARGET_FILE:lldb-rpc-gen> CACHE STRING "Executable that generates lldb-rpc-server")
+endif()