Merge pull request #3856 from augusto2112/read-cstrings-from-filecache-cherry-pick

[lldb] Make ReadCStringFromMemory default to read from the file-cache.

Author: augusto2112

lldb/include/lldb/Target/Target.h

@@ -1069,10 +1069,11 @@ class Target : public std::enable_shared_from_this<Target>,
                     lldb::addr_t *load_addr_ptr = nullptr);
 
   size_t ReadCStringFromMemory(const Address &addr, std::string &out_str,
-                               Status &error);
+                               Status &error, bool force_live_memory = false);
 
   size_t ReadCStringFromMemory(const Address &addr, char *dst,
-                               size_t dst_max_len, Status &result_error);
+                               size_t dst_max_len, Status &result_error,
+                               bool force_live_memory = false);
 
   size_t ReadScalarIntegerFromMemory(const Address &addr, uint32_t byte_size,
                                      bool is_signed, Scalar &scalar,

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.cpp

@@ -244,7 +244,11 @@ bool LLDBMemoryReader::readString(swift::remote::RemoteAddress address,
 
   Target &target(m_process.GetTarget());
   Status error;
-  target.ReadCStringFromMemory(addr, dest, error);
+  // We only want to allow the file-cache optimization if we resolved the 
+  // address to section + offset.
+  const bool force_live_memory =
+      !readMetadataFromFileCacheEnabled() || !addr.IsSectionOffset();
+  target.ReadCStringFromMemory(addr, dest, error, force_live_memory);
   if (error.Success()) {
     auto format_string = [](const std::string &dest) {
       StreamString stream;

lldb/source/Target/Target.cpp

@@ -1873,13 +1873,14 @@ size_t Target::ReadMemory(const Address &addr, void *dst, size_t dst_len,
 }
 
 size_t Target::ReadCStringFromMemory(const Address &addr, std::string &out_str,
-                                     Status &error) {
+                                     Status &error, bool force_live_memory) {
   char buf[256];
   out_str.clear();
   addr_t curr_addr = addr.GetLoadAddress(this);
   Address address(addr);
   while (true) {
-    size_t length = ReadCStringFromMemory(address, buf, sizeof(buf), error);
+    size_t length = ReadCStringFromMemory(address, buf, sizeof(buf), error,
+                                          force_live_memory);
     if (length == 0)
       break;
     out_str.append(buf, length);
@@ -1895,7 +1896,8 @@ size_t Target::ReadCStringFromMemory(const Address &addr, std::string &out_str,
 }
 
 size_t Target::ReadCStringFromMemory(const Address &addr, char *dst,
-                                     size_t dst_max_len, Status &result_error) {
+                                     size_t dst_max_len, Status &result_error,
+                                     bool force_live_memory) {
   size_t total_cstr_len = 0;
   if (dst && dst_max_len) {
     result_error.Clear();
@@ -1918,8 +1920,8 @@ size_t Target::ReadCStringFromMemory(const Address &addr, char *dst,
           cache_line_size - (curr_addr % cache_line_size);
       addr_t bytes_to_read =
           std::min<addr_t>(bytes_left, cache_line_bytes_left);
-      size_t bytes_read =
-          ReadMemory(address, curr_dst, bytes_to_read, error, true);
+      size_t bytes_read = ReadMemory(address, curr_dst, bytes_to_read, error,
+                                     force_live_memory);
 
       if (bytes_read == 0) {
         result_error = error;