[SH]tools/sh-demo: conveniently experiment with native compilation

sh-demo includes compilation of a .c file produced by `shermes` in the
regular CMake build, making it easy to experiment and test things.

tools/CMakeLists.txt

@@ -21,6 +21,7 @@ add_subdirectory(node-hermes)
 add_subdirectory(shermes)
 add_subdirectory(synth)
 add_subdirectory(hcdp)
+add_subdirectory(sh-demo)
 
 if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/facebook)
   add_subdirectory(facebook)

tools/sh-demo/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+link_libraries(shermes_console_a hermesvmlean_a jsi)
+link_libraries(setjmp)
+link_libraries(wasi-emulated-mman)
+
+add_executable(sh-demo demo.c cxa.cpp)

tools/sh-demo/cxa.cpp

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "llvh/Support/ErrorHandling.h"
+
+extern "C" void __cxa_throw(void* thrown_exception,
+    std::type_info* tinfo,
+    void (*dest)(void*)) {
+  llvh::report_fatal_error("C++ exceptions not supported on Wasi");
+}
+
+extern "C" void* __cxa_allocate_exception(size_t) {
+  llvh::report_fatal_error("C++ exceptions not supported on Wasi");
+}