build(WASI): Add shim for __cxa_thread_atexit

Not currently provided by the wasi toolchain. Needed by ITKElastix.

Probably safe to do nothing.

src/cxaThreadAtExitShim.cxx

@@ -0,0 +1,39 @@
+/*=========================================================================
+ *
+ *  Copyright NumFOCUS
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *         https://www.apache.org/licenses/LICENSE-2.0.txt
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *=========================================================================*/
+// Workaround for current lack of this function in the wasi toolchain
+// Ref: https://github.com/llvm/llvm-project/blob/80e2c26dfdd2e5ab1bbbf747ebff8c316399653c/libcxxabi/src/cxa_thread_atexit.cpp#L4
+
+#ifdef __cplusplus
+
+namespace __cxxabiv1 {
+
+  using Dtor = void(*)(void*);
+
+}
+
+extern "C" {
+
+int __cxa_thread_atexit(__cxxabiv1::Dtor dtor, void* obj, void* dso_symbol) throw()
+{
+  // Do nothing
+  return -1;
+}
+
+}
+
+#endif // __cplusplus

src/docker/itk-wasm/ITKWebAssemblyInterface.cmake

@@ -58,7 +58,7 @@ function(add_executable target)
     # WASI
     set_property(TARGET ${wasm_target} PROPERTY SUFFIX ".wasi.wasm")
     if (NOT TARGET wasi-itk-extras AND DEFINED CMAKE_CXX_COMPILE_OBJECT)
-      add_library(wasi-itk-extras STATIC /ITKWebAssemblyInterface/src/exceptionShim.cxx /ITKWebAssemblyInterface/src/initialization.cxx)
+      add_library(wasi-itk-extras STATIC /ITKWebAssemblyInterface/src/exceptionShim.cxx /ITKWebAssemblyInterface/src/cxaThreadAtExitShim.cxx /ITKWebAssemblyInterface/src/initialization.cxx)
     endif()
     get_property(_is_imported TARGET ${wasm_target} PROPERTY IMPORTED)
     if (NOT ${_is_imported})