[lldb] Add an extra optional did_read_live_memory to Target::ReadMemory (#149620)

Target::ReadMemory may or may not read live memory, but whether it did
read from live memory or from the filecache is opaque to callers. Add an
extra out parameter to indicate whether live memory was read or not.

Author: augusto2112

lldb/include/lldb/Target/Target.h

@@ -1110,10 +1110,16 @@ class Target : public std::enable_shared_from_this<Target>,
   // 2 - if there is a process, then read from memory
   // 3 - if there is no process, then read from the file cache
   //
+  // If did_read_live_memory is provided, will indicate if the read was from
+  // live memory, or from file contents. A caller which needs to treat these two
+  // sources differently should use this argument to disambiguate where the data
+  // was read from.
+  //
   // The method is virtual for mocking in the unit tests.
   virtual size_t ReadMemory(const Address &addr, void *dst, size_t dst_len,
                             Status &error, bool force_live_memory = false,
-                            lldb::addr_t *load_addr_ptr = nullptr);
+                            lldb::addr_t *load_addr_ptr = nullptr,
+                            bool *did_read_live_memory = nullptr);
 
   size_t ReadCStringFromMemory(const Address &addr, std::string &out_str,
                                Status &error, bool force_live_memory = false);

lldb/source/Target/Target.cpp

@@ -1987,8 +1987,11 @@ size_t Target::ReadMemoryFromFileCache(const Address &addr, void *dst,
 
 size_t Target::ReadMemory(const Address &addr, void *dst, size_t dst_len,
                           Status &error, bool force_live_memory,
-                          lldb::addr_t *load_addr_ptr) {
+                          lldb::addr_t *load_addr_ptr,
+                          bool *did_read_live_memory) {
   error.Clear();
+  if (did_read_live_memory)
+    *did_read_live_memory = false;
 
   Address fixed_addr = addr;
   if (ProcessIsValid())
@@ -2086,6 +2089,8 @@ size_t Target::ReadMemory(const Address &addr, void *dst, size_t dst_len,
       if (bytes_read) {
         if (load_addr_ptr)
           *load_addr_ptr = load_addr;
+        if (did_read_live_memory)
+          *did_read_live_memory = true;
         return bytes_read;
       }
     }

lldb/unittests/Expression/DWARFExpressionTest.cpp

@@ -111,7 +111,8 @@ class MockTarget : public Target {
 
   size_t ReadMemory(const Address &addr, void *dst, size_t dst_len,
                     Status &error, bool force_live_memory = false,
-                    lldb::addr_t *load_addr_ptr = nullptr) /*override*/ {
+                    lldb::addr_t *load_addr_ptr = nullptr,
+                    bool *did_read_live_memory = nullptr) /*override*/ {
     auto expected_memory = this->ReadMemory(addr.GetOffset(), dst_len);
     if (!expected_memory) {
       llvm::consumeError(expected_memory.takeError());