Fix debugger shutdown when Python interpreter is loaded

[ovyalov]

Summary

Python locks in memory a few global objects like lldb.debugger,lldb.target,... - as a consequence, ~Debugger isn't called upon shutdown.
Calling Debugger::Clear ensures that ScriptInterpreterPython::Clear is called to clean up Python global variables.

[zturner]

What were the symptoms of this? How'd you find it?

[ovyalov]

In D12683#241155, @zturner wrote:

What were the symptoms of this? How'd you find it?

I was debugging port forwarding with PlatformAndroid - in particular, whether forwarded ports are cleaned up with ~PlatformAndroidRemoteGDBServer. Turned out, that if there was at least one script command executed - platforms' destructors were never called.

[tfiala]

source/Core/Debugger.cpp

426

Wouldn't Clear() be considered a mutating function? So a const debugger ref seems like maybe it should be non-const?

i.e.
for (auto& debugger: debuggers) {

debugger->Clear();

}

[ovyalov]

source/Core/Debugger.cpp

426

Clear is mutable, but debugger has DebuggerSP type here - so, const is applicable only to shared_ptr, not to Debugger instance itself.

[tfiala]

source/Core/Debugger.cpp

426

Ah gotcha.

[clayborg]

Looks good.

[ovyalov]

Files:

/lldb/trunk/source/Core/Debugger.cpp

Users:

ovyalov (Author)

http://reviews.llvm.org/rL247023

source/Core/Debugger.cpp

 
 void
 Debugger::Terminate ()
 {
     assert(lldb_initialized && "Debugger::Terminate called without a matching Debugger::Initialize!");
 
     // Clear our master list of debugger objects
     Mutex::Locker locker (GetDebuggerListMutex ());
-    GetDebuggerList().clear();
+    auto& debuggers = GetDebuggerList();
+    for (const auto& debugger: debuggers)
+        debugger->Clear();
+
+    debuggers.clear();
 }
 
 void
 Debugger::SettingsInitialize ()
 {
     Target::SettingsInitialize ();
 }