Revert "[lldb] Do not use LC_FUNCTION_STARTS data to determine symbol size as symbols are created" (#108715)

Reverts #106791 because it breaks
`trap_frame_sym_ctx.test ` on x86_64.

https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/lldb-cmake/5745/

Author: JDevlieghere

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

@@ -3768,6 +3768,7 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
 
       SymbolType type = eSymbolTypeInvalid;
       SectionSP symbol_section;
+      lldb::addr_t symbol_byte_size = 0;
       bool add_nlist = true;
       bool is_gsym = false;
       bool demangled_is_synthesized = false;
@@ -4353,6 +4354,47 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
 
       if (symbol_section) {
         const addr_t section_file_addr = symbol_section->GetFileAddress();
+        if (symbol_byte_size == 0 && function_starts_count > 0) {
+          addr_t symbol_lookup_file_addr = nlist.n_value;
+          // Do an exact address match for non-ARM addresses, else get the
+          // closest since the symbol might be a thumb symbol which has an
+          // address with bit zero set.
+          FunctionStarts::Entry *func_start_entry =
+              function_starts.FindEntry(symbol_lookup_file_addr, !is_arm);
+          if (is_arm && func_start_entry) {
+            // Verify that the function start address is the symbol address
+            // (ARM) or the symbol address + 1 (thumb).
+            if (func_start_entry->addr != symbol_lookup_file_addr &&
+                func_start_entry->addr != (symbol_lookup_file_addr + 1)) {
+              // Not the right entry, NULL it out...
+              func_start_entry = nullptr;
+            }
+          }
+          if (func_start_entry) {
+            func_start_entry->data = true;
+
+            addr_t symbol_file_addr = func_start_entry->addr;
+            if (is_arm)
+              symbol_file_addr &= THUMB_ADDRESS_BIT_MASK;
+
+            const FunctionStarts::Entry *next_func_start_entry =
+                function_starts.FindNextEntry(func_start_entry);
+            const addr_t section_end_file_addr =
+                section_file_addr + symbol_section->GetByteSize();
+            if (next_func_start_entry) {
+              addr_t next_symbol_file_addr = next_func_start_entry->addr;
+              // Be sure the clear the Thumb address bit when we calculate the
+              // size from the current and next address
+              if (is_arm)
+                next_symbol_file_addr &= THUMB_ADDRESS_BIT_MASK;
+              symbol_byte_size = std::min<lldb::addr_t>(
+                  next_symbol_file_addr - symbol_file_addr,
+                  section_end_file_addr - symbol_file_addr);
+            } else {
+              symbol_byte_size = section_end_file_addr - symbol_file_addr;
+            }
+          }
+        }
         symbol_value -= section_file_addr;
       }
 
@@ -4459,6 +4501,9 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
       if (nlist.n_desc & N_WEAK_REF)
         sym[sym_idx].SetIsWeak(true);
 
+      if (symbol_byte_size > 0)
+        sym[sym_idx].SetByteSize(symbol_byte_size);
+
       if (demangled_is_synthesized)
         sym[sym_idx].SetDemangledNameIsSynthesized(true);
 
@@ -4577,7 +4622,23 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
           Address symbol_addr;
           if (module_sp->ResolveFileAddress(symbol_file_addr, symbol_addr)) {
             SectionSP symbol_section(symbol_addr.GetSection());
+            uint32_t symbol_byte_size = 0;
             if (symbol_section) {
+              const addr_t section_file_addr = symbol_section->GetFileAddress();
+              const FunctionStarts::Entry *next_func_start_entry =
+                  function_starts.FindNextEntry(func_start_entry);
+              const addr_t section_end_file_addr =
+                  section_file_addr + symbol_section->GetByteSize();
+              if (next_func_start_entry) {
+                addr_t next_symbol_file_addr = next_func_start_entry->addr;
+                if (is_arm)
+                  next_symbol_file_addr &= THUMB_ADDRESS_BIT_MASK;
+                symbol_byte_size = std::min<lldb::addr_t>(
+                    next_symbol_file_addr - symbol_file_addr,
+                    section_end_file_addr - symbol_file_addr);
+              } else {
+                symbol_byte_size = section_end_file_addr - symbol_file_addr;
+              }
               sym[sym_idx].SetID(synthetic_sym_id++);
               // Don't set the name for any synthetic symbols, the Symbol
               // object will generate one if needed when the name is accessed
@@ -4589,6 +4650,8 @@ void ObjectFileMachO::ParseSymtab(Symtab &symtab) {
               add_symbol_addr(symbol_addr.GetFileAddress());
               if (symbol_flags)
                 sym[sym_idx].SetFlags(symbol_flags);
+              if (symbol_byte_size)
+                sym[sym_idx].SetByteSize(symbol_byte_size);
               ++sym_idx;
             }
           }