diff --git a/CMakeLists.txt b/CMakeLists.txt
index a26fe2e2..bbb23dec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,11 +89,7 @@ set_target_properties(nlohmann_json::nlohmann_json PROPERTIES INTERFACE_INCLUDE_
 enable_testing()
 
 add_subdirectory(tools/kwgen)
-add_subdirectory(src/parser)
-add_subdirectory(src/ir)
-add_subdirectory(src/llvm)
-add_subdirectory(src/js)
-add_subdirectory(src/frontend)
+add_subdirectory(src)
 add_subdirectory(tests)
 
 configure_package_config_file(
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
new file mode 100644
index 00000000..121817df
--- /dev/null
+++ b/src/CMakeLists.txt
@@ -0,0 +1,25 @@
+# Copyright (c) 2023 Roberto Raggi <roberto.raggi@gmail.com>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+# the Software, and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+add_subdirectory(lib)
+add_subdirectory(parser)
+add_subdirectory(ir)
+add_subdirectory(llvm)
+add_subdirectory(js)
+add_subdirectory(frontend)
diff --git a/src/frontend/CMakeLists.txt b/src/frontend/CMakeLists.txt
index 509c9409..d2cb9d25 100644
--- a/src/frontend/CMakeLists.txt
+++ b/src/frontend/CMakeLists.txt
@@ -40,7 +40,8 @@ if(EMSCRIPTEN)
 endif()
 
 if (CMAKE_SYSTEM_NAME STREQUAL "WASI")
-    target_compile_definitions(cxx PUBLIC JSON_HAS_FILESYSTEM=0)
+    target_compile_definitions(cxx PRIVATE JSON_HAS_FILESYSTEM=0)
+    target_compile_definitions(cxx PRIVATE CXX_NO_FILESYSTEM)
 endif()
 
 if (CXX_INSTALL_TOOLS)
diff --git a/src/frontend/cxx/cli.cc b/src/frontend/cxx/cli.cc
index cc8946c6..b7a9c79b 100644
--- a/src/frontend/cxx/cli.cc
+++ b/src/frontend/cxx/cli.cc
@@ -214,6 +214,8 @@ auto CLI::positionals() const -> std::vector<std::string> {
 }
 
 void CLI::parse(int& argc, char**& argv) {
+  app_name = argv[0];
+
   for (int i = 1; i < argc;) {
     const std::string arg(argv[i++]);
 
diff --git a/src/frontend/cxx/cli.h b/src/frontend/cxx/cli.h
index df5d96e0..94190219 100644
--- a/src/frontend/cxx/cli.h
+++ b/src/frontend/cxx/cli.h
@@ -50,6 +50,7 @@ class CLI {
  public:
   CLI();
 
+  std::string app_name;
   bool opt_ast_dump = false;
   bool opt_ir_dump = false;
   bool opt_dM = false;
diff --git a/src/frontend/cxx/frontend.cc b/src/frontend/cxx/frontend.cc
index 3c3f4c54..30fdfb3e 100644
--- a/src/frontend/cxx/frontend.cc
+++ b/src/frontend/cxx/frontend.cc
@@ -31,6 +31,7 @@
 #include <cxx/macos_toolchain.h>
 #include <cxx/preprocessor.h>
 #include <cxx/private/format.h>
+#include <cxx/private/path.h>
 #include <cxx/recursive_ast_visitor.h>
 #include <cxx/scope.h>
 #include <cxx/symbol_printer.h>
@@ -245,6 +246,22 @@ auto runOnFile(const CLI& cli, const std::string& fileName) -> bool {
 
     if (auto paths = cli.get("--sysroot"); !paths.empty()) {
       wasmToolchain->setSysroot(paths.back());
+    } else {
+#if __wasi__
+      wasmToolchain->setSysroot("/wasi-sysroot");
+#elif __unix__
+      char* app_name = realpath(cli.app_name.c_str(), nullptr);
+
+      const fs::path app_dir = fs::path(app_name).remove_filename();
+      wasmToolchain->setAppdir(app_dir.string());
+
+      const auto sysroot_dir = app_dir / "../lib/wasi-sysroot";
+      wasmToolchain->setSysroot(sysroot_dir.string());
+
+      if (app_name) {
+        std::free(app_name);
+      }
+#endif
     }
 
     toolchain = std::move(wasmToolchain);
diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
new file mode 100644
index 00000000..844fb4a5
--- /dev/null
+++ b/src/lib/CMakeLists.txt
@@ -0,0 +1,23 @@
+# Copyright (c) 2023 Roberto Raggi <roberto.raggi@gmail.com>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+# the Software, and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+add_custom_target(link_wasi_sysroot ALL
+    COMMAND ${CMAKE_COMMAND} -E create_symlink ${wasi_sysroot_SOURCE_DIR} wasi-sysroot)
+
+add_subdirectory(cxx)
diff --git a/src/lib/cxx/CMakeLists.txt b/src/lib/cxx/CMakeLists.txt
new file mode 100644
index 00000000..562f46ef
--- /dev/null
+++ b/src/lib/cxx/CMakeLists.txt
@@ -0,0 +1,21 @@
+# Copyright (c) 2023 Roberto Raggi <roberto.raggi@gmail.com>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+# the Software, and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+add_custom_target(link_cxx_include ALL
+    COMMAND ${CMAKE_COMMAND} -E create_symlink ${CMAKE_CURRENT_SOURCE_DIR}/include include)
diff --git a/src/lib/cxx/include/stdarg.h b/src/lib/cxx/include/stdarg.h
new file mode 100644
index 00000000..47622a63
--- /dev/null
+++ b/src/lib/cxx/include/stdarg.h
@@ -0,0 +1,4 @@
+#pragma once
+
+typedef __builtin_va_list va_list;
+typedef __builtin_va_list __gnuc_va_list;
diff --git a/src/lib/cxx/include/stddef.h b/src/lib/cxx/include/stddef.h
new file mode 100644
index 00000000..69cf20bf
--- /dev/null
+++ b/src/lib/cxx/include/stddef.h
@@ -0,0 +1,13 @@
+#pragma once
+
+typedef long int ptrdiff_t;
+typedef long unsigned int size_t;
+typedef long unsigned int rsize_t;
+
+typedef struct {
+  long long __clang_max_align_nonce1
+      __attribute__((__aligned__(__alignof__(long long))));
+
+  long double __clang_max_align_nonce2
+      __attribute__((__aligned__(__alignof__(long double))));
+} max_align_t;
diff --git a/src/parser/cxx/wasm32_wasi_toolchain.cc b/src/parser/cxx/wasm32_wasi_toolchain.cc
index 6d964c37..d2a85dcd 100644
--- a/src/parser/cxx/wasm32_wasi_toolchain.cc
+++ b/src/parser/cxx/wasm32_wasi_toolchain.cc
@@ -25,6 +25,12 @@
 
 namespace cxx {
 
+const std::string& Wasm32WasiToolchain::appdir() const { return appdir_; }
+
+void Wasm32WasiToolchain::setAppdir(std::string appdir) {
+  appdir_ = std::move(appdir);
+}
+
 const std::string& Wasm32WasiToolchain::sysroot() const { return sysroot_; }
 
 void Wasm32WasiToolchain::setSysroot(std::string sysroot) {
@@ -34,16 +40,11 @@ void Wasm32WasiToolchain::setSysroot(std::string sysroot) {
 void Wasm32WasiToolchain::addSystemIncludePaths() {
   addSystemIncludePath(fmt::format("{}/include", sysroot_));
 
-  for (int version : {17, 16, 15, 14, 13, 12, 11, 10}) {
-    const auto path =
-        fs::path(fmt::format("/usr/lib/clang/{}/include", version));
-
-    if (exists(path)) {
-      version_ = version;
-      addSystemIncludePath(path.string());
-      break;
-    }
-  }
+#if __wasi__
+  addSystemIncludePath(fmt::format("/usr/lib/cxx/include", appdir_));
+#else
+  addSystemIncludePath(fmt::format("{}/../lib/cxx/include", appdir_));
+#endif
 }
 
 void Wasm32WasiToolchain::addSystemCppIncludePaths() {
diff --git a/src/parser/cxx/wasm32_wasi_toolchain.h b/src/parser/cxx/wasm32_wasi_toolchain.h
index 922d3b68..0980a71b 100644
--- a/src/parser/cxx/wasm32_wasi_toolchain.h
+++ b/src/parser/cxx/wasm32_wasi_toolchain.h
@@ -31,6 +31,9 @@ class Wasm32WasiToolchain final : public Toolchain {
  public:
   using Toolchain::Toolchain;
 
+  const std::string& appdir() const;
+  void setAppdir(std::string appdir);
+
   const std::string& sysroot() const;
   void setSysroot(std::string sysroot);
 
@@ -39,6 +42,7 @@ class Wasm32WasiToolchain final : public Toolchain {
   void addPredefinedMacros() override;
 
  private:
+  std::string appdir_;
   std::string sysroot_;
   std::optional<int> version_;
 };