wasm2c: Use wrappers for function references (#2465)

Clang 17(?) tightened UBSAN checks, so that you now get this:

```
- test/wasm2c/spec/call_indirect.txt
  expected error code 0, got 1.
  STDERR MISMATCH:
  --- expected
  +++ actual
  @@ -0,0 +1,3 @@
  +out/test/wasm2c/spec/call_indirect/call_indirect.0.c:2144:12: runtime error: call to function w2c_call__indirect__0__wasm_f0 through pointer to incorrect function type 'unsigned int (*)(void *)'
  +/home/runner/work/wabt/wabt/out/test/wasm2c/spec/call_indirect/call_indirect.0.c:1925: note: w2c_call__indirect__0__wasm_f0 defined here
  +SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior out/test/wasm2c/spec/call_indirect/call_indirect.0.c:2144:12 
  STDOUT MISMATCH:
  --- expected
  +++ actual
  @@ -1 +0,0 @@
  -134/134 tests passed.
```

This happens because emitted functions use a typed module instance,
while function references use a `void*` instance. It is UB in C to call
the former with the latter, so clang is correct here.

We had to pick one of two ways to fix this: either emit `void*` wrapper
functions that do the appropriate downcasting for any module functions
that go into a table (potentially including imported functions), or the
approach that takes significantly less effort of changing everything to
`void*` and downcasting internally. ~~We obviously chose the latter.~~
We eventually started emitting wrapper functions.

1 files changed, 5 insertions, 1 deletions

diff --git a/test/wasm2c/tail-calls.txt b/test/wasm2c/tail-calls.txt
index b27d7417..bbc02c07 100644
--- a/test/wasm2c/tail-calls.txt
+++ b/test/wasm2c/tail-calls.txt
@@ -811,8 +811,12 @@ FUNC_TYPE_T(w2c_test_i32_f32) = "\x98\x89\x5c\xbd\x28\xfd\x0e\x4d\xc5\xdc\x68\x2
 FUNC_TYPE_T(w2c_test_t1) = "\x36\xa9\xe7\xf1\xc9\x5b\x82\xff\xb9\x97\x43\xe0\xc5\xc4\xce\x95\xd8\x3c\x9a\x43\x0a\xac\x59\xf8\x4e\xf3\xcb\xfa\xb6\x14\x50\x68";
 FUNC_TYPE_T(w2c_test_t2) = "\xe5\x11\x86\xc7\x24\xdb\x44\x80\xbe\xd1\xe0\x89\xbc\xc0\x20\xea\xfb\x1c\x9a\x27\xa5\xc3\xdb\xca\x5d\xb0\x05\x0f\x7c\x03\x74\x0a";
 
+static void wrap_w2c_spectest_print_i32_f32(void *instance, u32 var_0, f32 var_1) {
+  return w2c_spectest_print_i32_f32(instance, var_0, var_1);
+}
+
 static const wasm_elem_segment_expr_t elem_segment_exprs_w2c_test_e0[] = {
-  {RefFunc, w2c_test_i32_f32, (wasm_rt_function_ptr_t)w2c_spectest_print_i32_f32, {wasm_tailcall_w2c_spectest_print_i32_f32}, offsetof(w2c_test, w2c_spectest_instance)},
+  {RefFunc, w2c_test_i32_f32, (wasm_rt_function_ptr_t)wrap_w2c_spectest_print_i32_f32, {wasm_tailcall_w2c_spectest_print_i32_f32}, offsetof(w2c_test, w2c_spectest_instance)},
 };
 
 static void init_tables(w2c_test* instance) {