[AGENT++] [BUG] Access to freed memory during startup of snmp++v3.2.24 with agent++v3.5.30

[Dominik Vogt]

The problem is even worse; it also affects creating the logging entries.
I did not have time to analyse the problem yet, but this is the output
of insure++ (in this specific case it's not a crash but a memory
violation).  (snmp++v3.2.24 and agent++v3.5.30, both compiled with the
default configuration).  The only other hint I have is that the problem
also occured during or shortly after startup of the program, but that
may be just by chance.

--
[log.h:155] **READ_DANGLING**
>>         unsigned char get_class(void) const { return type & 0xF0; }

  Reading from a dangling pointer: this, while accessing field "type"

  Pointer : 0x097193c8
  In block: 0x097193c8 thru 0x097193df (24 bytes)
                  new LogEntryImpl, allocated at log.cpp, 338
                          malloc()  (interface)
                    operator new()
  AgentLogImpl::create_log_entry()  log.cpp, 338
    DefaultLog::create_log_entry()  ../include/snmp_pp/log.h, 499
         Agentpp::thread_starter()  threads.cpp, 482

stack trace where memory was freed:
                            free()  (interface)
                 operator delete()
     LogEntryImpl::~LogEntryImpl()  log.cpp, 192
    DefaultLog::delete_log_entry()  ../include/snmp_pp/log.h, 515
Agentpp::TaskManager::TaskManager()  threads.cpp, 761
 Agentpp::ThreadPool::ThreadPool()  threads.cpp, 864
Agentpp::QueuedThreadPool::QueuedThreadPool()  threads.cpp, 882
[snip]
           __do_global_ctors_aux()
                           _init()
                       call_init()
                        _dl_init()

  Stack trace where the error occurred:
             LogEntry::get_class()  ../include/snmp_pp/log.h, 155
        AgentLogImpl::operator+=()  log.cpp, 352
         Agentpp::thread_starter()  threads.cpp, 485
--

log.h:499 is this code:

  static void create_log_entry(unsigned char t)
    { if (!entry) { entry = log()->create_log_entry(t);
entry->init();} }

So despite the locking in the macros LOG_BEGIN and LOG_END, I managed
to corrupt the member "entry" of the class DefaultLog.

Ciao

Dominik ^_^  ^_^