[lldb] [llvm] [lldb-dap] Add support for data breakpoint. (PR #81541)

[Zequan Wu via llvm-commits]

================
@@ -561,6 +561,46 @@ void EventThreadFunction() {
   }
 }
 
+lldb::SBValue FindVariable(uint64_t variablesReference, llvm::StringRef name) {
+  lldb::SBValue variable;
+  if (lldb::SBValueList *top_scope = GetTopLevelScope(variablesReference)) {
+    bool is_duplicated_variable_name = name.contains(" @");
+    // variablesReference is one of our scopes, not an actual variable it is
+    // asking for a variable in locals or globals or registers
+    int64_t end_idx = top_scope->GetSize();
+    // Searching backward so that we choose the variable in closest scope
+    // among variables of the same name.
+    for (int64_t i = end_idx - 1; i >= 0; --i) {
+      lldb::SBValue curr_variable = top_scope->GetValueAtIndex(i);
+      std::string variable_name = CreateUniqueVariableNameForDisplay(
+          curr_variable, is_duplicated_variable_name);
----------------
ZequanWu wrote:

This functions is shared between `request_setVariable` and `request_dataBreakpointInfo`, so it checks name that contains `foo @ main.cpp:12`. I tested this manually.

For anonymous unions inside struct, I also tested manually. If we watch either `c` or `d`, changes on either value stops the program as expected.
```
struct A {
  int a;
  int b;
  union {
    char c;
    int d;
  };
};
```

https://github.com/llvm/llvm-project/pull/81541