[Expressions] Add support of expressions evaluation in some object's context

Summary:
This patch adds support of expression evaluation in a context of some object.
Consider the following example:
```
struct S {
  int a = 11;
  int b = 12;
};

int main() {
  S s;
  int a = 1;
  int b = 2;
  // We have stopped here
  return 0;
}
```
This patch allows to do something like that:
```
lldb.frame.FindVariable("s").EvaluateExpression("a + b")
```
and the result will be `33` (not `3`) because fields `a` and `b` of `s` will be
used (not locals `a` and `b`).

This is achieved by replacing of `this` type and object for the expression. This
has some limitations: an expression can be evaluated only for values located in
the debuggee process memory (they must have an address of `eAddressTypeLoad`
type).

Reviewers: teemperor, clayborg, jingham, zturner, labath, davide, spyffe, serge-sans-paille

Reviewed By: jingham

Subscribers: abidh, lldb-commits, leonid.mashinskiy

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D55318

llvm-svn: 353149

1 files changed, 9 insertions, 7 deletions

diff --git a/lldb/source/Expression/ExpressionSourceCode.cpp b/lldb/source/Expression/ExpressionSourceCode.cpp
index d19321a429e..a146472c26c 100644
--- a/lldb/source/Expression/ExpressionSourceCode.cpp
+++ b/lldb/source/Expression/ExpressionSourceCode.cpp
@@ -178,7 +178,8 @@ static void AddLocalVariableDecls(const lldb::VariableListSP &var_list_sp,
 bool ExpressionSourceCode::GetText(std::string &text,
                                    lldb::LanguageType wrapping_language,
                                    bool static_method,
-                                   ExecutionContext &exe_ctx) const {
+                                   ExecutionContext &exe_ctx,
+                                   bool add_locals) const {
   const char *target_specific_defines = "typedef signed char BOOL;\n";
   std::string module_macros;
 
@@ -251,12 +252,13 @@ bool ExpressionSourceCode::GetText(std::string &text,
       }
     }
 
-    ConstString object_name;
-    if (Language::LanguageIsCPlusPlus(frame->GetLanguage())) {
-      if (target->GetInjectLocalVariables(&exe_ctx)) {
-        lldb::VariableListSP var_list_sp =
-            frame->GetInScopeVariableList(false, true);
-        AddLocalVariableDecls(var_list_sp, lldb_local_var_decls);
+    if (add_locals) {
+      if (Language::LanguageIsCPlusPlus(frame->GetLanguage())) {
+        if (target->GetInjectLocalVariables(&exe_ctx)) {
+          lldb::VariableListSP var_list_sp =
+              frame->GetInScopeVariableList(false, true);
+          AddLocalVariableDecls(var_list_sp, lldb_local_var_decls);
+        }
       }
     }
   }