[debugserver] Clear memory allocations after exec

[bulbazord]

Summary

After an exec, the inferior is a new process and none of these memory
regions are still allocated. Clear them out.

[jasonmolenda]

LGTM.

lldb/tools/debugserver/source/MacOSX/MachProcess.mm

if (m_pid != 0) {
           DNBLog("arch changed from 0x%8.8x to 0x%8.8x", m_cpu_type,
                  process_cpu_type);
           m_cpu_type = process_cpu_type;
           DNBArchProtocol::SetArchitecture(process_cpu_type);
         }
         m_thread_list.Clear();
         m_activities.Clear();
         m_breakpoints.DisableAll();
+        m_task.ClearAllocations();
       }
 
       if (m_sent_interrupt_signo != 0) {
         if (received_interrupt) {
           DNBLogThreadedIf(LOG_PROCESS,
                            "MachProcess::ExceptionMessageBundleComplete(): "
                            "process successfully interrupted with signal %i",
                            m_sent_interrupt_signo);

lldb/tools/debugserver/source/MacOSX/MachTask.h

public:
 
   nub_size_t ReadMemory(nub_addr_t addr, nub_size_t size, void *buf);
   nub_size_t WriteMemory(nub_addr_t addr, nub_size_t size, const void *buf);
   int GetMemoryRegionInfo(nub_addr_t addr, DNBRegionInfo *region_info);
   std::string GetProfileData(DNBProfileDataScanType scanType);
 
   nub_addr_t AllocateMemory(nub_size_t size, uint32_t permissions);
   nub_bool_t DeallocateMemory(nub_addr_t addr);
+  void ClearAllocations();
 
   mach_port_t ExceptionPort() const;
   bool ExceptionPortIsValid() const;
   kern_return_t SaveExceptionPortInfo();
   kern_return_t RestoreExceptionPortInfo();
   kern_return_t ShutDownExcecptionThread();
 
   bool StartExceptionThread(

lldb/tools/debugserver/source/MacOSX/MachTask.mm

#define ALWAYS_ZOMBIE_ALLOCATIONS 0
         return true;
       } else
         return ::mach_vm_deallocate(task, addr, size) == KERN_SUCCESS;
     }
   }
   return false;
 }
 
+//----------------------------------------------------------------------
+// MachTask::ClearAllocations
+//----------------------------------------------------------------------
+void MachTask::ClearAllocations() {
+  m_allocations.clear();
+}
+
 void MachTask::TaskPortChanged(task_t task)
 {
   m_task = task;
 
   // If we've just exec'd to a new process, and it
   // is started suspended, we'll need to do two
   // task_resume's to get the inferior process to
   // continue.
   if (m_exec_will_be_suspended)
     m_do_double_resume = true;
   else
     m_do_double_resume = false;
   m_exec_will_be_suspended = false;
 }