[Lldb-commits] [lldb] [lldb] Report the unwound PC for WebAssembly caller frames (PR #212326)

[Felipe de Azevedo Piovezan via lldb-commits]

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@@ -64,9 +64,21 @@ const RegisterSet *RegisterContextWasm::GetRegisterSet(size_t reg_set) {
 
 bool RegisterContextWasm::ReadRegister(const RegisterInfo *reg_info,
                                        RegisterValue &value) {
-  // The only real registers is the PC.
-  if (reg_info->name)
+  // The only real register is the PC.
+  if (reg_info->name) {
+    // A caller frame's PC is the unwound return address, which the base
+    // register context cannot provide because it only sees the innermost
+    // frame's live PC. Use the PC the unwinder recorded for this frame.
+    if (m_concrete_frame_idx > 0) {
+      ThreadWasm &wasm_thread = static_cast<ThreadWasm &>(GetThread());
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felipepiovezan wrote:

I don't want to open a patch now to avoid any conflicts, but on line 84 we have:

```
  ThreadWasm *thread = static_cast<ThreadWasm *>(&GetThread());
  ProcessWasm *process = static_cast<ProcessWasm *>(thread->GetProcess().get());
  if (!thread)
    return false;
```

It also declares a ThreadWasm variable, and does a null test which is non-sensical (the variable starts as a reference, and a static cast will never turn non-null into null).

I think it is defensible to hoist your variable to the function scope and delete the `if` in this PR, since you are indirectly re-using existing code. But I'm also happy to put a patch after you merge this.

https://github.com/llvm/llvm-project/pull/212326