[DynamicLoader] Make sure we always set the rendezvous breakpoint

Summary:
Once we've attached to the process we load all current modules and also set a breakpoint at the rendezvous break address.
However, we don't do this if we already have a load address for the image info address (e.g.: DT_DEBUG on ELF). This code was added 4 years ago when adding support for `$qXfer:Libraries:` packet (https://reviews.llvm.org/D9471) but its intention is not 100% clear to me. It seems to me we're using that check to know if the modules have already been loaded (which they have if `$qXfer:Libraries:` is supported by the gdb server) and skip loading the modules again in the following `if` block. The problem is that we also skip setting the Rendezvous breakpoint so we stop knowing when the process loads new modules.
I fix this by moving the call to set the breakpoint to the end of the function so we always call it as long as we have a valid executable.

Reviewers: ADodds, clayborg, eugene, labath

Reviewed By: eugene, labath

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D62168

llvm-svn: 362619

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp

@@ -150,11 +150,6 @@ void DynamicLoaderPOSIXDYLD::DidAttach() {
                          true);
 
     LoadAllCurrentModules();
-    if (!SetRendezvousBreakpoint()) {
-      // If we cannot establish rendezvous breakpoint right now we'll try again
-      // at entry point.
-      ProbeEntry();
-    }
 
     m_process->GetTarget().ModulesDidLoad(module_list);
     if (log) {
@@ -169,6 +164,14 @@ void DynamicLoaderPOSIXDYLD::DidAttach() {
       }
     }
   }
+
+  if (executable_sp.get()) {
+    if (!SetRendezvousBreakpoint()) {
+      // If we cannot establish rendezvous breakpoint right now we'll try again
+      // at entry point.
+      ProbeEntry();
+    }
+  }
 }
 
 void DynamicLoaderPOSIXDYLD::DidLaunch() {