Properly unload modules from target image list when using svr4 packets

[fjricci]

Summary

When we receive an svr4 packet from the remote, we check for new modules
and add them to the list of images in the target. However, we did not
do the same for modules which have been removed.

This was causing TestLoadUnload to fail when using ds2, which uses
svr4 packets to communicate all library info on Linux. This patch fixes
the failing test.

[tfiala]

source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

4907

It looks like this code will unload any modules currently listed as loaded via m_process->GetTarget().GetImages(), if they do not appear in the module_list argument to this function. Is that correct behavior? (It might be, but that's not what I would have guessed without digging deeper).

I might be not following the flow here correctly, though. Can you clarify? Did the full test suite run with this change? Thanks!

[fjricci]

source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

4907

So yes, this will remove any existing modules that are not in the svr4 packet, provided that there were modules listed in the svr4 packet (indicating that the remote is using the packet) - if new_modules.GetSize() == 0, we won't remove anything.

As far as I can tell from the gdb protocol specs, the svr4 packet should contain a list of all loaded libraries, so as long as the svr4 packet contains libraries, I believe that removing modules which are no longer listed is the correct behavior.

I did run the full suite on linux (with lldb-server), and it passes with this change.

As a side note, the module_list argument is actually an output parameter, filled by GetLoadedModuleList().

[tfiala]

LGTM.

source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

4907

Oh of course I see the flow.

[ADodds]

Looks fine to me.

source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

for (LoadedModuleInfoList::LoadedModuleInfo & modInfo : module_list.m_list)
                                                         mod_base_is_offset);
 
         if (module_sp.get())
             new_modules.Append (module_sp);
     }
 
     if (new_modules.GetSize() > 0)
     {
+        ModuleList removed_modules;
         Target &target = GetTarget();
+        ModuleList &loaded_modules = m_process->GetTarget().GetImages();
+
+        for (size_t i = 0; i < loaded_modules.GetSize(); ++i)
+        {
+            const lldb::ModuleSP loaded_module = loaded_modules.GetModuleAtIndex(i);
+
+            bool found = false;
+            for (size_t j = 0; j < new_modules.GetSize(); ++j)
+            {
+                if (new_modules.GetModuleAtIndex(j).get() == loaded_module.get())
+                    found = true;
+            }
+
+            if (!found)
+            {
+                lldb_private::ObjectFile * obj = loaded_module->GetObjectFile ();
+                if (obj && obj->GetType () != ObjectFile::Type::eTypeExecutable)
+                    removed_modules.Append (loaded_module);
+            }
+        }
+
+        loaded_modules.Remove (removed_modules);
+        m_process->GetTarget().ModulesDidUnload (removed_modules, false);
 
         new_modules.ForEach ([&target](const lldb::ModuleSP module_sp) -> bool
         {
             lldb_private::ObjectFile * obj = module_sp->GetObjectFile ();
             if (!obj)
                 return true;
 
             if (obj->GetType () != ObjectFile::Type::eTypeExecutable)
                 return true;
 
             lldb::ModuleSP module_copy_sp = module_sp;
             target.SetExecutableModule (module_copy_sp, false);
             return false;
         });
 
-        ModuleList &loaded_modules = m_process->GetTarget().GetImages();
         loaded_modules.AppendIfNeeded (new_modules);
         m_process->GetTarget().ModulesDidLoad (new_modules);
     }
 
     return new_modules.GetSize();
-
 }
 
 size_t
 ProcessGDBRemote::LoadModules ()
 {
     LoadedModuleInfoList module_list;
     return LoadModules (module_list);
 }