diff --git a/0001-Apply-fix-for-bad-path-in-clang-12.patch b/0001-Apply-fix-for-bad-path-in-clang-12.patch
new file mode 100644
index 0000000..0e0b6a6
--- /dev/null
+++ b/0001-Apply-fix-for-bad-path-in-clang-12.patch
@@ -0,0 +1,37 @@
+From 99a42933ac1cd839a19781f09d1b12b4bce27778 Mon Sep 17 00:00:00 2001
+From: Seth Foster <seth@opentrons.com>
+Date: Thu, 22 Jul 2021 16:28:24 -0400
+Subject: [PATCH] Apply fix for bad path in clang 12
+
+---
+ CMakeLists.txt | 9 ++++++++-
+ 1 file changed, 8 insertions(+), 1 deletion(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 923b4d9..e7ccfea 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,5 +1,4 @@
+ cmake_minimum_required(VERSION 3.4.3)
+-
+ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+   message(STATUS "IWYU: out-of-tree configuration")
+   set(IWYU_IN_TREE OFF)
+@@ -17,6 +16,14 @@ if (NOT IWYU_IN_TREE)
+   project(include-what-you-use)
+ 
+   find_package(LLVM CONFIG REQUIRED)
++
++  if (APPLE)
++    if (LLVM_VERSION_MAJOR EQUAL 12)
++      set_target_properties(LLVMSupport PROPERTIES
++        INTERFACE_LINK_LIBRARIES "m;ZLIB::ZLIB;curses;LLVMDemangle")
++    endif()
++  endif()
++
+   find_package(Clang CONFIG REQUIRED)
+ 
+   list(APPEND CMAKE_MODULE_PATH ${LLVM_DIR})
+-- 
+2.30.1 (Apple Git-130)
+
diff --git a/FindClang.cmake b/FindClang.cmake
index 3f157d0..7afd5a2 100644
--- a/FindClang.cmake
+++ b/FindClang.cmake
@@ -22,10 +22,12 @@ but other useful tools built on the clang frontend, such as clang-format and Cod
 
 Provides the variables
 - ``Clang_FOUND``: bool, true if found
-- ``Clang_EXECUTABLE``: the path to the clang frontend binary
+- ``Clang_EXECUTABLE``: the path to the clang (c) frontend binary
+- ``ClangXX_EXECUTABLE``: the path to the clang++ (c++) frontend binary
 - ``Clang_CLANGTIDY_EXECUTABLE``: the path to clang-tidy
 - ``Clang_CLANGFORMAT_EXECUTABLE``: the path to clang-format
 - ``Clang_CODECHECKER_EXECUTABLE``: the path to CodeChecker
+- ``Clang_DIRECTORY``: The path to the downloaded clang tree
 
 #]=======================================================================]
 
@@ -49,32 +51,39 @@ FetchContent_Declare(CLANG_LOCALINSTALL
   DOWNLOAD_DIR "${LOCALINSTALL_CLANG_DIR}/${CMAKE_HOST_SYSTEM_NAME}"
   URL "https://github.com/llvm/llvm-project/releases/download/llvmorg-${DL_CLANG_VERSION}/clang+llvm-${DL_CLANG_VERSION}-${CLANG_ARCHIVE}")
 
-FetchContent_GetProperties(CLANG_LOCALINSTALL
-  POPULATED CLANG_LOCALINSTALL_POPULATED)
-if(NOT CLANG_LOCALINSTALL_POPULATED)
+FetchContent_GetProperties(CLANG_LOCALINSTALL)
+if(NOT clang_localinstall_POPULATED)
   FetchContent_Populate(CLANG_LOCALINSTALL)
   message(STATUS "Downloaded new clang")
 endif()
 
 find_program(Clang_EXECUTABLE
   clang
-  PATHS ${CMAKE_SOURCE_DIR}/stm32-tools/clang/${CMAKE_HOST_SYSTEM_NAME}
-  PATH_SUFFIXES bin)
+  PATHS ${clang_localinstall_SOURCE_DIR}
+  PATH_SUFFIXES bin
+  NO_DEFAULT_PATH)
+
+find_program(ClangXX_EXECUTABLE
+  clang++
+  PATHS ${clang_localinstall_SOURCE_DIR}
+  PATH_SUFFIXES bin
+  NO_DEFAULT_PATH)
 
 find_program(Clang_CLANGFORMAT_EXECUTABLE
   clang-format
-  PATHS ${CMAKE_SOURCE_DIR}/stm32-tools/clang/${CMAKE_HOST_SYSTEM_NAME}
+  PATHS ${clang_localinstall_SOURCE_DIR}
   PATH_SUFFIXES bin
   NO_DEFAULT_PATH)
 
 find_program(Clang_CLANGTIDY_EXECUTABLE
   clang-tidy
-  PATHS ${CMAKE_SOURCE_DIR}/stm32-tools/clang/${CMAKE_HOST_SYSTEM_NAME}
-  PATH_SUFFIXES bin)
+  PATHS ${clang_localinstall_SOURCE_DIR}
+  PATH_SUFFIXES bin
+  NO_DEFAULT_PATH)
 
 find_program(Clang_CODECHECKER_EXECUTABLE
   CodeChecker
-  PATHS ${CMAKE_SOURCE_DIR}/stm32-tools/clang/${CMAKE_HOST_SYSTEM_NAME})
+  PATHS ${clang_localinstall_SOURCE_DIR})
 
 if (Clang_CODECHECKER_EXECUTABLE STREQUAL "Clang_CODECHECKER_EXECUTABLE_NOTFOUND")
   message(WARNING "Could not find codechecker, which is system-dependent. See https://codechecker.readthedocs.io/en/latest/#install-guide")
@@ -135,5 +144,7 @@ if (${INSTALLED_CLANG_VERSION} VERSION_LESS ${DL_CLANG_VERSION})
   endif()
 endif()
 
+set(Clang_DIRECTORY ${clang_localinstall_SOURCE_DIR})
+
 message(STATUS "Found clang-tidy at: ${Clang_CLANGTIDY_EXECUTABLE}")
 message(STATUS "Found clang-format at ${Clang_CLANGFORMAT_EXECUTABLE}")
diff --git a/FindIncludeWhatYouUse.cmake b/FindIncludeWhatYouUse.cmake
new file mode 100644
index 0000000..31aa0eb
--- /dev/null
+++ b/FindIncludeWhatYouUse.cmake
@@ -0,0 +1,103 @@
+#[=======================================================================[.rst:
+FindIncludeWhatYouUse.cmake
+---------------------------
+
+This module is intended for use with ``find_package`` and should not be imported on
+its own.
+
+It provides include-what-you-use (https://github.com/include-what-you-use/include-what-you-use/tree/clang_12),
+an add-on tool that ensures that all headers necessary to make a specific c++ file
+work are included and no headers that are not necessary are included.
+
+It will download (if necessary) the include-what-you-use source (there is no binary
+distribution provided) and compile it into the build directory. It will then create
+an appropriate invocation string in ``CMAKE_CXX_INCLUDE_WHAT_YOU_USE`` and
+``CMAKE_C_INCLUDE_WHAT_YOU_USE`` so that the tool will be run alongside compilation.
+
+The only necessary integration point should be calling
+``find_package(IncludeWhatYouUse)``.
+
+Provides the variables
+- ``IncludeWhatYouUse_FOUND``: bool, true if found
+- ``IncludeWhatYouUse_EXECUTABLE``: the path to the iwyu binary
+- ``CMAKE_CXX_INCLUDE_WHAT_YOU_USE``: internal variable with invocation command
+- ``CMAKE_C_INCLUDE_WHAT_YOU_USE``: internal variable with invocation command
+
+#]=======================================================================]
+
+find_package(Clang REQUIRED)
+find_package(Patch REQUIRED)
+
+set(LOCALINSTALL_IWYU_DIR "${CMAKE_SOURCE_DIR}/stm32-tools/iwyu")
+set(DL_IWYU_VERSION "0.16")
+
+message(STATUS "installing include-what-you-use ${DL_IWYU_VERSION} to ${LOCALINSTALL_IWYU_DIR}")
+
+FetchContent_Declare(IWYU_LOCALINSTALL
+  PREFIX "${LOCALINSTALL_IWYU_DIR}/${CMAKE_HOST_SYSTEM_NAME}"
+  # Patch does this: https://lists.llvm.org/pipermail/llvm-dev/2021-June/151554.html
+  PATCH_COMMAND ${Patch_EXECUTABLE} -i ${CMAKE_CURRENT_LIST_DIR}/0001-Apply-fix-for-bad-path-in-clang-12.patch
+  URL "https://include-what-you-use.org/downloads/include-what-you-use-${DL_IWYU_VERSION}.src.tar.gz")
+
+FetchContent_GetProperties(IWYU_LOCALINSTALL)
+
+if(NOT IWYU_LOCALINSTALL_POPULATED)
+  message(STATUS "Downloading iwyu")
+  FetchContent_Populate(IWYU_LOCALINSTALL)
+  FetchContent_GetProperties(IWYU_LOCALINSTALL)
+  message(STATUS "Downloaded iwyu")
+  message(STATUS "configuring iwyu for build ${iwyu_localinstall_BINARY_DIR} from ${iwyu_localinstall_SOURCE_DIR}")
+
+  execute_process(
+    COMMAND ${CMAKE_COMMAND} -DCMAKE_C_COMPILER=${Clang_EXECUTABLE} -DCMAKE_CXX_COMPILER=${ClangXX_EXECUTABLE} -DCMAKE_PREFIX_PATH=${Clang_DIRECTORY} -DCMAKE_VERBOSE_MAKEFILE=1 ${iwyu_localinstall_SOURCE_DIR}
+    COMMAND_ECHO STDOUT
+    WORKING_DIRECTORY ${iwyu_localinstall_BINARY_DIR}
+    COMMAND_ERROR_IS_FATAL ANY)
+  message(STATUS "building iwyu")
+  execute_process(
+    COMMAND make
+    COMMAND_ECHO STDOUT
+    WORKING_DIRECTORY ${iwyu_localinstall_BINARY_DIR}
+    COMMAND_ERROR_IS_FATAL ANY)
+  message(STATUS "built to ${iwyu_localinstall_BINARY_DIR}")
+endif()
+find_program(IncludeWhatYouUse_EXECUTABLE
+  include-what-you-use
+  PATHS ${iwyu_localinstall_BINARY_DIR}/bin
+  NO_DEFAULT_PATH
+  REQUIRED)
+set(IncludeWhatYouUse_FOUND TRUE)
+set(IncludeWhatYouUse_DIRECTORY ${iwyu_localinstall_BINARY_DIR})
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Gnu")
+  # If the compiler is gcc, then we need to make sure that iwyu (which uses
+  # clang to function) is using the appropriate standard library and system
+  # headers
+  find_library(
+    LIBSTDCPP
+    NAMES "libstdc++" "stdc++"
+    REQUIRED
+    HINTS /usr/local/lib)
+  find_path(
+    LIBSTDCPP_INC
+    NAMES array
+    HINTS /usr/local/include
+    REQUIRED
+    )
+  find_path(
+    LIBSTDCPP_BITS
+    NAMES "c++config.h"
+    HINTS /usr/local/include
+    REQUIRED
+    )
+
+  cmake_path(GET ${LIBSTDCPP_BITS} PARENT_PATH syspath)
+  set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE
+    "${IncludeWhatYouUse_EXECUTABLE}"
+    -stdlib=libstdc++
+    -stdlib++-isystem=${LIBSTDCPP_INC}
+    -cxx-isystem${syspath}
+    )
+else()
+  set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE "${IncludeWhatYouUse_EXECUTABLE}")
+endif()
+set(CMAKE_C_INCLUDE_WHAT_YOU_USE "${IncludeWhatYouUse_EXECUTABLE}")