1 files changed, 44 insertions, 24 deletions

diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index a19322f..f31b56b 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -918,6 +918,11 @@ ConstString ObjectFileMachO::GetSectionNameEHFrame() {
   return g_section_name_eh_frame;
 }
 
+ConstString ObjectFileMachO::GetSectionNameLLDBNoNlist() {
+  static ConstString g_section_name_lldb_no_nlist("__lldb_no_nlist");
+  return g_section_name_lldb_no_nlist;
+}
+
 bool ObjectFileMachO::MagicBytesMatch(DataBufferSP data_sp,
                                       lldb::addr_t data_offset,
                                       lldb::addr_t data_length) {
@@ -2394,8 +2399,39 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
   uint32_t memory_module_load_level = eMemoryModuleLoadLevelComplete;
   bool is_shared_cache_image = IsSharedCacheBinary();
   bool is_local_shared_cache_image = is_shared_cache_image && !IsInMemory();
+
+  ConstString g_segment_name_TEXT = GetSegmentNameTEXT();
+  ConstString g_segment_name_DATA = GetSegmentNameDATA();
+  ConstString g_segment_name_DATA_DIRTY = GetSegmentNameDATA_DIRTY();
+  ConstString g_segment_name_DATA_CONST = GetSegmentNameDATA_CONST();
+  ConstString g_segment_name_OBJC = GetSegmentNameOBJC();
+  ConstString g_section_name_eh_frame = GetSectionNameEHFrame();
+  ConstString g_section_name_lldb_no_nlist = GetSectionNameLLDBNoNlist();
+  SectionSP text_section_sp(
+      section_list->FindSectionByName(g_segment_name_TEXT));
+  SectionSP data_section_sp(
+      section_list->FindSectionByName(g_segment_name_DATA));
   SectionSP linkedit_section_sp(
       section_list->FindSectionByName(GetSegmentNameLINKEDIT()));
+  SectionSP data_dirty_section_sp(
+      section_list->FindSectionByName(g_segment_name_DATA_DIRTY));
+  SectionSP data_const_section_sp(
+      section_list->FindSectionByName(g_segment_name_DATA_CONST));
+  SectionSP objc_section_sp(
+      section_list->FindSectionByName(g_segment_name_OBJC));
+  SectionSP eh_frame_section_sp;
+  SectionSP lldb_no_nlist_section_sp;
+  if (text_section_sp.get()) {
+    eh_frame_section_sp = text_section_sp->GetChildren().FindSectionByName(
+        g_section_name_eh_frame);
+    lldb_no_nlist_section_sp = text_section_sp->GetChildren().FindSectionByName(
+        g_section_name_lldb_no_nlist);
+  } else {
+    eh_frame_section_sp =
+        section_list->FindSectionByName(g_section_name_eh_frame);
+    lldb_no_nlist_section_sp =
+        section_list->FindSectionByName(g_section_name_lldb_no_nlist);
+  }
 
   if (process && m_header.filetype != llvm::MachO::MH_OBJECT &&
       !is_local_shared_cache_image) {
@@ -2403,6 +2439,14 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
 
     memory_module_load_level = target.GetMemoryModuleLoadLevel();
 
+    // If __TEXT,__lldb_no_nlist section is present in this binary,
+    // and we're reading it out of memory, do not read any of the
+    // nlist entries.  They are not needed in lldb and it may be
+    // expensive to load these.  This is to handle a dylib consisting
+    // of only metadata, no code, but it has many nlist entries.
+    if (lldb_no_nlist_section_sp)
+      memory_module_load_level = eMemoryModuleLoadLevelMinimal;
+
     // Reading mach file from memory in a process or core file...
 
     if (linkedit_section_sp) {
@@ -2526,30 +2570,6 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
 
   const bool have_strtab_data = strtab_data.GetByteSize() > 0;
 
-  ConstString g_segment_name_TEXT = GetSegmentNameTEXT();
-  ConstString g_segment_name_DATA = GetSegmentNameDATA();
-  ConstString g_segment_name_DATA_DIRTY = GetSegmentNameDATA_DIRTY();
-  ConstString g_segment_name_DATA_CONST = GetSegmentNameDATA_CONST();
-  ConstString g_segment_name_OBJC = GetSegmentNameOBJC();
-  ConstString g_section_name_eh_frame = GetSectionNameEHFrame();
-  SectionSP text_section_sp(
-      section_list->FindSectionByName(g_segment_name_TEXT));
-  SectionSP data_section_sp(
-      section_list->FindSectionByName(g_segment_name_DATA));
-  SectionSP data_dirty_section_sp(
-      section_list->FindSectionByName(g_segment_name_DATA_DIRTY));
-  SectionSP data_const_section_sp(
-      section_list->FindSectionByName(g_segment_name_DATA_CONST));
-  SectionSP objc_section_sp(
-      section_list->FindSectionByName(g_segment_name_OBJC));
-  SectionSP eh_frame_section_sp;
-  if (text_section_sp.get())
-    eh_frame_section_sp = text_section_sp->GetChildren().FindSectionByName(
-        g_section_name_eh_frame);
-  else
-    eh_frame_section_sp =
-        section_list->FindSectionByName(g_section_name_eh_frame);
-
   const bool is_arm = (m_header.cputype == llvm::MachO::CPU_TYPE_ARM);
   const bool always_thumb = GetArchitecture().IsAlwaysThumbInstructions();