docs: add exception handling toolchain compatibility guide

docs/develop/c/exception_handling.md

@@ -0,0 +1,60 @@
+---
+sidebar_position: 6
+---
+
+# Exception Handling
+
+WasmEdge implements the [latest exception-handling proposal](https://github.com/WebAssembly/exception-handling) (post Oct 2023). Legacy EH instructions such as `delegate` are rejected at load time.
+
+Enable the proposal when running or compiling:
+
+```bash
+wasmedge --enable-exception-handling module.wasm
+wasmedge compile --enable-exception-handling module.wasm module.aot.wasm
+```
+
+## Toolchain compatibility
+
+| Toolchain | Version | Compatible | Notes |
+|-----------|---------|------------|-------|
+| WasmEdge (runtime) | 0.17.x | Yes | Latest EH proposal; use `--enable-exception-handling` |
+| Emscripten (`-fwasm-exceptions`) | 3.1.64, 6.0.0 | No | Emits legacy EH (e.g. opcode `0x117` / `delegate`) |
+| `wasm-3.0-exceptions` spec tests | wasmedge-spectest | Yes | Official test inputs used by WasmEdge CI |
+
+WasmEdge does not plan to support legacy EH. Use modules built for the current proposal only.
+
+## How WasmEdge tests EH
+
+CI runs the `wasm-3.0-exceptions` suite from [wasmedge-spectest](https://github.com/WasmEdge/wasmedge-spectest). See `test/spec/CMakeLists.txt` in the [WasmEdge](https://github.com/WasmEdge/WasmEdge) repository.
+
+To run a spec test locally after building tests, or fetch a `.wasm` from that repository:
+
+```bash
+wasmedge --enable-exception-handling path/to/test.wasm
+```
+
+## Emscripten repro (expected failure today)
+
+`a.cpp`:
+
+```cpp
+#include <stdio.h>
+
+int main() {
+  try {
+    puts("throw...");
+    throw 1;
+    puts("(never reached)");
+  } catch (...) {
+    puts("catch!");
+  }
+  return 0;
+}
+```
+
+```bash
+emcc -O1 -fwasm-exceptions -sSTANDALONE_WASM a.cpp -o a.wasm
+wasmedge --enable-exception-handling a.wasm
+```
+
+Typical error: `loading failed: illegal opcode, Code: 0x117` (`Deprecated delegate instruction`).