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/check-imports.txt b/test/wasm2c/check-imports.txt
index f2fe508e..0947a201 100644
--- a/test/wasm2c/check-imports.txt
+++ b/test/wasm2c/check-imports.txt
@@ -802,11 +802,15 @@ FUNC_TYPE_T(w2c_test_t0) = "\x07\x80\x96\x7a\x42\xf7\x3e\xe6\x70\x5c\x2f\xac\x83
 FUNC_TYPE_T(w2c_test_t1) = "\x72\xab\x00\xdf\x20\x3d\xce\xa1\xf2\x29\xc7\x9d\x13\x40\x7e\x98\xac\x7d\x41\x4a\x53\x2e\x42\x42\x61\x55\x2e\xaa\xeb\xbe\xc6\x35";
 FUNC_TYPE_T(w2c_test_t2) = "\x92\xfb\x6a\xdf\x49\x07\x0a\x83\xbe\x08\x02\x68\xcd\xf6\x95\x27\x4a\xc2\xf3\xe5\xe4\x7d\x29\x49\xe8\xed\x42\x92\x6a\x9d\xda\xf0";
 
+static u32 wrap_w2c_test_f1(void *instance) {
+  return w2c_test_f1(instance);
+}
+
 static void init_memories(w2c_test* instance) {
 }
 
 static const wasm_elem_segment_expr_t elem_segment_exprs_w2c_test_e0[] = {
-  {RefFunc, w2c_test_t1, (wasm_rt_function_ptr_t)w2c_test_f1, {NULL}, 0},
+  {RefFunc, w2c_test_t1, (wasm_rt_function_ptr_t)wrap_w2c_test_f1, {NULL}, 0},
 };
 
 static void init_tables(w2c_test* instance) {