[LLDB] Support GNU-style compressed debug sections (.zdebug)

[davide]

This requires an unittest (or an lldb-test test). Some comments inline.
I think @clayborg or @jasonmolenda are in a better position to review the structure, I can take a look at the ELF specific details.

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1890–1891

this whole cascade is really not ideal. Maybe we should factor the checks out or move this to be a switch?

2113–2115

Please remove references to GOOGLE3.

[aprantl]

Which compilers / platforms generate / support this? Is this an ELF-only feature?

[clayborg]

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

2937–2938

Might be worth making these llvm::StringRef, then see comments below..

2948

Make this a StringRef:

llvm::StringRef section_name = section->GetName().GetStringRef();

2954–2955

use StringRef::startswith:

if (section_name.startswith(debug_prefix) || section_name.startswith(zdebug_prefix))

3451

use "section_name" here instead of "section->GetName().GetStringRef()" since we switched it to a StringRef

3472

Ditto

[clayborg]

If this is for current and future debugging, it would be nice to change the tool to just use the normal .debug prefixes and just specify SHF_COMPRESSED???

[dblaikie]

In D45628#1067375, @aprantl wrote:

Which compilers / platforms generate / support this? Is this an ELF-only feature?

Clang/LLVM do (-Wa,--compress-debug-sections). Yeah, it's ELF only so far as I know. There's a couple of variations (-compress-debug-sections=zlib or zlib-gnu) the ".zdebug_foo" is zlib-gnu style, but a more modern variant (zlib) uses a section attribute SHF_COMPRESSED instead of the name mangling.

In D45628#1067382, @clayborg wrote:

If this is for current and future debugging, it would be nice to change the tool to just use the normal .debug prefixes and just specify SHF_COMPRESSED???

At least for now, zlib-gnu style is used at Google - I don't actually know what it'd cost to switch to the more modern zlib (using SHF_COMPRESSED) style. No doubt there are a variety of tools that may not have been updated/improved to support the new format - hard to say.

[aprantl]

Thanks for clarifying. You'll also need to add a testcase. If clang supports this then I don't have a problem with supporting this in LLDB and adding a testcase should be easy.

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1893

Could this entire device be replaced by a llvm::StringSwitch or something else more elegant?

[clayborg]

We should test both ways: using normal DWARF section names with SHF_COMPRESSED, and with ".zdebug" prefixed section names.

[alur]

I refactored the code to address the comments on it. I'll add those tests once I get the test runner to work.

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1893

I moved it out into a separate method with a StringSwitch

3451

This is a separate method, which doesn't have a section_name variable.

3472

Same here.

[davide]

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1773–1781

Thanks! This was exactly what I had in mind. Do you mind to split the NFC changes into a separate patch (that can be committed without review)? This will make this patch much easier to review.

[labath]

Thank you for the patch. For testing I'd recommend taking a look at r320813 https://reviews.llvm.org/D40616, which implemented the SHF_COMPRESSED part of the compressed section support. It looks like we should add a new field to the "lldb-test module-sections" output, so that we can test the section type computation code.

[alur]

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1773–1781

Sure, attached it here.

nfc.patch15 KBDownload

[alur]

Changed the diff to be against the NFCs.

[clayborg]

Very nice!

[davide]

Some minor comments, almost ready to go. Do you have commit access or you need somebody to push this on your behalf?

packages/Python/lldbsuite/test/linux/compressed-debug-info/TestCompressedDebugInfo.py

23–41

This test is too much boilerplate. We moved to a new, more concise style. You might consider using

(target, process, thread, main_breakpoint) = lldbutil.run_to_source_breakpoint(self, 
        "break here", src_file_spec, exe_name = exe)

instead.

48–65

ditto.

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

1778–1781

Can you add a comment to explain why are you dropping the first two character here?

[alur]

Thank you, I do need someone to push this on my behalf.

[alur]

Friendly ping, is there anything else I need to do for this to get submitted?

[lemo]

Hi Erik, the review is still marked as requiring changes. Once that is
sorted out I'd be happy to submit this on your behalf (what is the base SVN
revision for the latest patch?)

Davide Italiano, is all the CR feedback addressed in the latest revision?

[davide]

This is fine, I'll commit it for you today.

[alur]

Thank you David.

This is still based on the latest revision of the file (+ the non functional change patch).

nfc.patch15 KBDownload

[alur]

Since there was some changes to the file during the last couple of days I've updated the patches to be against HEAD again.

The new NFC patch:

nfc.patch135 KBDownload

[alur]

Updated the diff to be against head, again.

[alur]

Friendly ping on this again. I re-merged the patch against head.

packages/Python/lldbsuite/test/linux/compressed-debug-info/Makefile

+LEVEL := ../../make
+
+C_SOURCES := a.c
+
+all: compressed.out compressed.gnu.out
+
+compressed.out: a.out
+  $(OBJCOPY) --compress-debug-sections=zlib $< $@
+
+compressed.gnu.out: a.out
+  $(OBJCOPY) --compress-debug-sections=zlib-gnu $< $@
+
+include $(LEVEL)/Makefile.rules
+
+clean::
+  $(RM) -f a.o main compressed.out compressed.gnu.out

packages/Python/lldbsuite/test/linux/compressed-debug-info/TestCompressedDebugInfo.py

+""" Tests that compressed debug info sections are used. """
+import os
+import lldb
+import sys
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCompressedDebugInfo(TestBase):
+  mydir = TestBase.compute_mydir(__file__)
+
+  def setUp(self):
+    TestBase.setUp(self)
+
+  @no_debug_info_test  # Prevent the genaration of the dwarf version of this test
+  @skipUnlessPlatform(["linux"])
+  def test_compressed_debug_info(self):
+    """Tests that the 'frame variable' works with compressed debug info."""
+
+    self.build()
+    process = lldbutil.run_to_source_breakpoint(
+        self, "main", lldb.SBFileSpec("a.c"), exe_name="compressed.out")[1]
+
+    # The process should be stopped at a breakpoint, and the z variable should
+    # be in the top frame.
+    self.assertTrue(process.GetState() == lldb.eStateStopped,
+                    STOPPED_DUE_TO_BREAKPOINT)
+    frame = process.GetThreadAtIndex(0).GetFrameAtIndex(0)
+    self.assertTrue(frame.FindVariable("z").IsValid(), "z is not valid")
+
+  @no_debug_info_test  # Prevent the genaration of the dwarf version of this test
+  @skipUnlessPlatform(["linux"])
+  def test_compressed_debug_info_gnu(self):
+    """Tests that the 'frame variable' works with gnu-style compressed debug info."""
+
+    self.build()
+    process = lldbutil.run_to_source_breakpoint(
+        self, "main", lldb.SBFileSpec("a.c"), exe_name="compressed.gnu.out")[1]
+
+    # The process should be stopped at a breakpoint, and the z variable should
+    # be in the top frame.
+    self.assertTrue(process.GetState() == lldb.eStateStopped,
+                    STOPPED_DUE_TO_BREAKPOINT)
+    frame = process.GetThreadAtIndex(0).GetFrameAtIndex(0)
+    self.assertTrue(frame.FindVariable("z").IsValid(), "z is not valid")

packages/Python/lldbsuite/test/linux/compressed-debug-info/a.c

+int main() {
+  int z = 2;
+  return z;
+}

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

   if (!name || !name[0] || !ParseSectionHeaders())
     return 0;
   for (size_t i = 1; i < m_section_headers.size(); ++i)
     if (m_section_headers[i].section_name == ConstString(name))
       return i;
   return 0;
 }
 
+static SectionType getSectionType(llvm::StringRef section_name) {
+  if (!section_name.startswith(".")) {
+    return eSectionTypeOther;
+  }
+
+  // MISSING? .gnu_debugdata - "mini debuginfo / MiniDebugInfo" section,
+  // http://sourceware.org/gdb/onlinedocs/gdb/MiniDebugInfo.html
+  // MISSING? .debug-index -
+  // http://src.chromium.org/viewvc/chrome/trunk/src/build/gdb-add-index?pathrev=144644
+  return llvm::StringSwitch<SectionType>(section_name.drop_front(1))
+      .Case("text", eSectionTypeCode)
+      .Case("data", eSectionTypeData)
+      .Case("bss", eSectionTypeZeroFill)
+      .Case("tdata", eSectionTypeData)
+      .Case("tbss", eSectionTypeZeroFill)
+      // Abbreviations used in the .debug_info section
+      .Case("debug_abbrev", eSectionTypeDWARFDebugAbbrev)
+      .Case("debug_abbrev.dwo", eSectionTypeDWARFDebugAbbrev)
+      .Case("debug_addr", eSectionTypeDWARFDebugAddr)
+      // Lookup table for mapping addresses to compilation units
+      .Case("debug_aranges", eSectionTypeDWARFDebugAranges)
+      .Case("debug_cu_index", eSectionTypeDWARFDebugCuIndex)
+      // Call frame information
+      .Case("debug_frame", eSectionTypeDWARFDebugFrame)
+      // The core DWARF information section
+      .Case("debug_info", eSectionTypeDWARFDebugInfo)
+      .Case("debug_info.dwo", eSectionTypeDWARFDebugInfo)
+      // Line number information
+      .Case("debug_line", eSectionTypeDWARFDebugLine)
+      .Case("debug_line.dwo", eSectionTypeDWARFDebugLine)
+      // Location lists used in DW_AT_location attributes
+      .Case("debug_loc", eSectionTypeDWARFDebugLoc)
+      .Case("debug_loc.dwo", eSectionTypeDWARFDebugLoc)
+      // Macro information
+      .Case("debug_macinfo", eSectionTypeDWARFDebugMacInfo)
+      .Case("debug_macro", eSectionTypeDWARFDebugMacro)
+      .Case("debug_macro.dwo", eSectionTypeDWARFDebugMacro)
+      // Lookup table for mapping object and function names to compilation units
+      .Case("debug_pubnames", eSectionTypeDWARFDebugPubNames)
+      // Lookup table for mapping type names to compilation units
+      .Case("debug_pubtypes", eSectionTypeDWARFDebugPubTypes)
+      // Address ranges used in DW_AT_ranges attributes
+      .Case("debug_ranges", eSectionTypeDWARFDebugRanges)
+      // String table used in .debug_info
+      .Case("debug_str", eSectionTypeDWARFDebugStr)
+      .Case("debug_str.dwo", eSectionTypeDWARFDebugStr)
+      .Case("debug_str_offsets", eSectionTypeDWARFDebugStrOffsets)
+      .Case("debug_str_offsets.dwo", eSectionTypeDWARFDebugStrOffsets)
+      .Case("debug_types", eSectionTypeDWARFDebugTypes)
+      .Case("gnu_debugaltlink", eSectionTypeDWARFGNUDebugAltLink)
+      .Case("eh_frame", eSectionTypeEHFrame)
+      .Case("ARM.exidx", eSectionTypeARMexidx)
+      .Case("ARM.extab", eSectionTypeARMextab)
+      .Case("gosymtab", eSectionTypeGoSymtab)
+      .Default(eSectionTypeOther);
+}
+
 void ObjectFileELF::CreateSections(SectionList &unified_section_list) {
   if (!m_sections_ap.get() && ParseSectionHeaders()) {
     m_sections_ap.reset(new SectionList());
 
     // Object files frequently have 0 for every section address, meaning we
     // need to compute synthetic addresses in order for "file addresses" from
     // different sections to not overlap
     bool synthaddrs = (CalculateType() == ObjectFile::Type::eTypeObjectFile);
     uint64_t nextaddr = 0;
 
     for (SectionHeaderCollIter I = m_section_headers.begin();
          I != m_section_headers.end(); ++I) {
       const ELFSectionHeaderInfo &header = *I;
 
-      ConstString &name = I->section_name;
+      llvm::StringRef section_name = I->section_name.GetStringRef();
       const uint64_t file_size =
           header.sh_type == SHT_NOBITS ? 0 : header.sh_size;
       const uint64_t vm_size = header.sh_flags & SHF_ALLOC ? header.sh_size : 0;
 
-      static ConstString g_sect_name_text(".text");
-      static ConstString g_sect_name_data(".data");
-      static ConstString g_sect_name_bss(".bss");
-      static ConstString g_sect_name_tdata(".tdata");
-      static ConstString g_sect_name_tbss(".tbss");
-      static ConstString g_sect_name_dwarf_debug_abbrev(".debug_abbrev");
-      static ConstString g_sect_name_dwarf_debug_addr(".debug_addr");
-      static ConstString g_sect_name_dwarf_debug_aranges(".debug_aranges");
-      static ConstString g_sect_name_dwarf_debug_cu_index(".debug_cu_index");
-      static ConstString g_sect_name_dwarf_debug_frame(".debug_frame");
-      static ConstString g_sect_name_dwarf_debug_info(".debug_info");
-      static ConstString g_sect_name_dwarf_debug_line(".debug_line");
-      static ConstString g_sect_name_dwarf_debug_loc(".debug_loc");
-      static ConstString g_sect_name_dwarf_debug_macinfo(".debug_macinfo");
-      static ConstString g_sect_name_dwarf_debug_macro(".debug_macro");
-      static ConstString g_sect_name_dwarf_debug_pubnames(".debug_pubnames");
-      static ConstString g_sect_name_dwarf_debug_pubtypes(".debug_pubtypes");
-      static ConstString g_sect_name_dwarf_debug_ranges(".debug_ranges");
-      static ConstString g_sect_name_dwarf_debug_str(".debug_str");
-      static ConstString g_sect_name_dwarf_debug_str_offsets(
-          ".debug_str_offsets");
-      static ConstString g_sect_name_dwarf_debug_abbrev_dwo(
-          ".debug_abbrev.dwo");
-      static ConstString g_sect_name_dwarf_debug_info_dwo(".debug_info.dwo");
-      static ConstString g_sect_name_dwarf_debug_line_dwo(".debug_line.dwo");
-      static ConstString g_sect_name_dwarf_debug_macro_dwo(".debug_macro.dwo");
-      static ConstString g_sect_name_dwarf_debug_loc_dwo(".debug_loc.dwo");
-      static ConstString g_sect_name_dwarf_debug_str_dwo(".debug_str.dwo");
-      static ConstString g_sect_name_dwarf_debug_str_offsets_dwo(
-          ".debug_str_offsets.dwo");
-      static ConstString g_sect_name_dwarf_debug_types(".debug_types");
-      static ConstString g_sect_name_eh_frame(".eh_frame");
-      static ConstString g_sect_name_arm_exidx(".ARM.exidx");
-      static ConstString g_sect_name_arm_extab(".ARM.extab");
-      static ConstString g_sect_name_go_symtab(".gosymtab");
-      static ConstString g_sect_name_dwarf_gnu_debugaltlink(".gnu_debugaltlink");
-
-      SectionType sect_type = eSectionTypeOther;
-
-      bool is_thread_specific = false;
-
-      if (name == g_sect_name_text)
-        sect_type = eSectionTypeCode;
-      else if (name == g_sect_name_data)
-        sect_type = eSectionTypeData;
-      else if (name == g_sect_name_bss)
-        sect_type = eSectionTypeZeroFill;
-      else if (name == g_sect_name_tdata) {
-        sect_type = eSectionTypeData;
-        is_thread_specific = true;
-      } else if (name == g_sect_name_tbss) {
-        sect_type = eSectionTypeZeroFill;
-        is_thread_specific = true;
-      }
-      // .debug_abbrev – Abbreviations used in the .debug_info section
-      // .debug_aranges – Lookup table for mapping addresses to compilation
-      // units .debug_frame – Call frame information .debug_info – The core
-      // DWARF information section .debug_line – Line number information
-      // .debug_loc – Location lists used in DW_AT_location attributes
-      // .debug_macinfo – Macro information .debug_pubnames – Lookup table
-      // for mapping object and function names to compilation units
-      // .debug_pubtypes – Lookup table for mapping type names to compilation
-      // units .debug_ranges – Address ranges used in DW_AT_ranges attributes
-      // .debug_str – String table used in .debug_info MISSING?
-      // .gnu_debugdata - "mini debuginfo / MiniDebugInfo" section,
-      // http://sourceware.org/gdb/onlinedocs/gdb/MiniDebugInfo.html MISSING?
-      // .debug-index - http://src.chromium.org/viewvc/chrome/trunk/src/build
-      // /gdb-add-index?pathrev=144644 MISSING? .debug_types - Type
-      // descriptions from DWARF 4? See
-      // http://gcc.gnu.org/wiki/DwarfSeparateTypeInfo
-      else if (name == g_sect_name_dwarf_debug_abbrev)
-        sect_type = eSectionTypeDWARFDebugAbbrev;
-      else if (name == g_sect_name_dwarf_debug_addr)
-        sect_type = eSectionTypeDWARFDebugAddr;
-      else if (name == g_sect_name_dwarf_debug_aranges)
-        sect_type = eSectionTypeDWARFDebugAranges;
-      else if (name == g_sect_name_dwarf_debug_cu_index)
-        sect_type = eSectionTypeDWARFDebugCuIndex;
-      else if (name == g_sect_name_dwarf_debug_frame)
-        sect_type = eSectionTypeDWARFDebugFrame;
-      else if (name == g_sect_name_dwarf_debug_info)
-        sect_type = eSectionTypeDWARFDebugInfo;
-      else if (name == g_sect_name_dwarf_debug_line)
-        sect_type = eSectionTypeDWARFDebugLine;
-      else if (name == g_sect_name_dwarf_debug_loc)
-        sect_type = eSectionTypeDWARFDebugLoc;
-      else if (name == g_sect_name_dwarf_debug_macinfo)
-        sect_type = eSectionTypeDWARFDebugMacInfo;
-      else if (name == g_sect_name_dwarf_debug_macro)
-        sect_type = eSectionTypeDWARFDebugMacro;
-      else if (name == g_sect_name_dwarf_debug_pubnames)
-        sect_type = eSectionTypeDWARFDebugPubNames;
-      else if (name == g_sect_name_dwarf_debug_pubtypes)
-        sect_type = eSectionTypeDWARFDebugPubTypes;
-      else if (name == g_sect_name_dwarf_debug_ranges)
-        sect_type = eSectionTypeDWARFDebugRanges;
-      else if (name == g_sect_name_dwarf_debug_str)
-        sect_type = eSectionTypeDWARFDebugStr;
-      else if (name == g_sect_name_dwarf_debug_types)
-        sect_type = eSectionTypeDWARFDebugTypes;
-      else if (name == g_sect_name_dwarf_debug_str_offsets)
-        sect_type = eSectionTypeDWARFDebugStrOffsets;
-      else if (name == g_sect_name_dwarf_debug_abbrev_dwo)
-        sect_type = eSectionTypeDWARFDebugAbbrev;
-      else if (name == g_sect_name_dwarf_debug_info_dwo)
-        sect_type = eSectionTypeDWARFDebugInfo;
-      else if (name == g_sect_name_dwarf_debug_line_dwo)
-        sect_type = eSectionTypeDWARFDebugLine;
-      else if (name == g_sect_name_dwarf_debug_macro_dwo)
-        sect_type = eSectionTypeDWARFDebugMacro;
-      else if (name == g_sect_name_dwarf_debug_loc_dwo)
-        sect_type = eSectionTypeDWARFDebugLoc;
-      else if (name == g_sect_name_dwarf_debug_str_dwo)
-        sect_type = eSectionTypeDWARFDebugStr;
-      else if (name == g_sect_name_dwarf_debug_str_offsets_dwo)
-        sect_type = eSectionTypeDWARFDebugStrOffsets;
-      else if (name == g_sect_name_eh_frame)
-        sect_type = eSectionTypeEHFrame;
-      else if (name == g_sect_name_arm_exidx)
-        sect_type = eSectionTypeARMexidx;
-      else if (name == g_sect_name_arm_extab)
-        sect_type = eSectionTypeARMextab;
-      else if (name == g_sect_name_go_symtab)
-        sect_type = eSectionTypeGoSymtab;
-      else if (name == g_sect_name_dwarf_gnu_debugaltlink)
-        sect_type = eSectionTypeDWARFGNUDebugAltLink;
+      SectionType sect_type = getSectionType(section_name);
+      bool is_thread_specific =
+          section_name.equals(".tdata") || section_name.equals(".tbss");
 
       const uint32_t permissions =
           ((header.sh_flags & SHF_ALLOC) ? ePermissionsReadable : 0u) |
           ((header.sh_flags & SHF_WRITE) ? ePermissionsWritable : 0u) |
           ((header.sh_flags & SHF_EXECINSTR) ? ePermissionsExecutable : 0u);
       switch (header.sh_type) {
       case SHT_SYMTAB:
         assert(sect_type == eSectionTypeOther);


               ? m_arch_spec.GetDataByteSize()
               : eSectionTypeCode == sect_type ? m_arch_spec.GetCodeByteSize()
                                               : 1;
       elf::elf_xword log2align =
           (header.sh_addralign == 0) ? 0 : llvm::Log2_64(header.sh_addralign);
 
       uint64_t addr = header.sh_addr;
 
       if ((header.sh_flags & SHF_ALLOC) && synthaddrs) {
           nextaddr =
               (nextaddr + header.sh_addralign - 1) & ~(header.sh_addralign - 1);
           addr = nextaddr;
           nextaddr += vm_size;
       }
 
       SectionSP section_sp(new Section(
           GetModule(), // Module to which this section belongs.
           this, // ObjectFile to which this section belongs and should read
                 // section data from.
           SectionIndex(I),     // Section ID.
-          name,                // Section name.
+          I->section_name,     // Section name.
           sect_type,           // Section type.
           addr,                // VM address.
           vm_size,             // VM size in bytes of this section.
           header.sh_offset,    // Offset of this section in the file.
           file_size,           // Size of the section as found in the file.
           log2align,           // Alignment of the section
           header.sh_flags,     // Flags for this section.
           target_bytes_size)); // Number of host bytes per target byte
 
       section_sp->SetPermissions(permissions);
       if (is_thread_specific)
         section_sp->SetIsThreadSpecific(is_thread_specific);
       m_sections_ap->AddSection(section_sp);
     }
   }
 
   // For eTypeDebugInfo files, the Symbol Vendor will take care of updating the
   // unified section list.
   if (GetType() != eTypeDebugInfo)
     unified_section_list = *m_sections_ap;

     m_symtab_ap->CalculateSymbolSizes();
   }
 
   return m_symtab_ap.get();
 }
 
 void ObjectFileELF::RelocateSection(lldb_private::Section *section)
 {
-  static const char *debug_prefix = ".debug";
+  static const llvm::StringRef debug_prefix(".debug");
 
   // Set relocated bit so we stop getting called, regardless of whether we
   // actually relocate.
   section->SetIsRelocated(true);
 
   // We only relocate in ELF relocatable files
   if (CalculateType() != eTypeObjectFile)
     return;
 
-  const char *section_name = section->GetName().GetCString();
+  llvm::StringRef section_name = section->GetName().GetStringRef();
   // Can't relocate that which can't be named
-  if (section_name == nullptr)
+  if (section_name.empty())
     return;
 
   // We don't relocate non-debug sections at the moment
-  if (strncmp(section_name, debug_prefix, strlen(debug_prefix)))
+  if (section_name.startswith(debug_prefix))
     return;
 
   // Relocation section names to look for
-  std::string needle = std::string(".rel") + section_name;
-  std::string needlea = std::string(".rela") + section_name;
+  std::string needle = std::string(".rel") + section_name.str();
+  std::string needlea = std::string(".rela") + section_name.str();
 
   for (SectionHeaderCollIter I = m_section_headers.begin();
        I != m_section_headers.end(); ++I) {
     if (I->sh_type == SHT_RELA || I->sh_type == SHT_REL) {
       const char *hay_name = I->section_name.GetCString();
       if (hay_name == nullptr)
         continue;
       if (needle == hay_name || needlea == hay_name) {

 void ObjectFileELF::ParseUnwindSymbols(Symtab *symbol_table,
                                        DWARFCallFrameInfo *eh_frame) {
   SectionList *section_list = GetSectionList();
   if (!section_list)
     return;
 
   // First we save the new symbols into a separate list and add them to the
   // symbol table after we colleced all symbols we want to add. This is
-  // neccessary because adding a new symbol invalidates the internal index of
+  // necessary because adding a new symbol invalidates the internal index of
   // the symtab what causing the next lookup to be slow because it have to
   // recalculate the index first.
   std::vector<Symbol> new_symbols;
 
   eh_frame->ForEachFDEEntries([this, symbol_table, section_list, &new_symbols](
       lldb::addr_t file_addr, uint32_t size, dw_offset_t) {
     Symbol *symbol = symbol_table->FindSymbolAtFileAddress(file_addr);
     if (symbol) {
       if (!symbol->GetByteSizeIsValid()) {
         symbol->SetByteSize(size);
         symbol->SetSizeIsSynthesized(true);
       }
     } else {
       SectionSP section_sp =
           section_list->FindSectionContainingFileAddress(file_addr);
       if (section_sp) {
         addr_t offset = file_addr - section_sp->GetFileAddress();
         const char *symbol_name = GetNextSyntheticSymbolName().GetCString();
         uint64_t symbol_id = symbol_table->GetNumSymbols();
         Symbol eh_symbol(