[reSIProcate] removing hash<T*> from HashMap

[Bruce Lowekamp]

I think there's still an underlying problem that there's a hidden  
operator== (operator< on win32) that would be needed.  I don't know  
of a generic way around those, although if someone else does, I would  
love to hear about it.

Bruce

On Apr 23, 2008, at 4:26 PM, Byron Campen wrote:
> 	Would it be reasonable to change the impl to call t->hash()? (I  
> suppose we could get oddball behavior if t->hash() happened to  
> return something interesting)
>
> Best regards,
> Byron Campen
>
>>
>> I would like to check in a change to HashMap to fix a problem that
>> has occasionally bitten me in other code (not resip itself) that uses
>> rutil.  HashMap.hxx defines a generic hash<T*> function object that
>> allows any code:
>> HashMap<foo*, bar>
>> to compile by using the address of the pointer itself as the hash.
>> This obviously fails for any key that can exist in multiple places in
>> the system.
>>
>> This isn't an issue in resip itself as far as I can tell---in fact
>> the only use of the hash<T*> in the code that I've been able to find
>> is for a HashMap<pthread_t,> on macosx.  And in this case, it's easy
>> enough to restore the previous behavior by using the HashValue
>> macros.  But having that template in the header file allows some code
>> to compile that I would really not allow to compile---ever.
>>
>> Thoughts on whether this change would cause any problems?
>>
>> Bruce
>>
>>
>>
>> $svn diff
>> Index: rutil/Log.cxx
>> ===================================================================
>> --- rutil/Log.cxx       (revision 7627)
>> +++ rutil/Log.cxx       (working copy)
>> @@ -39,6 +39,9 @@
>>
>>
>>   #ifdef LOG_ENABLE_THREAD_SETTING
>> +#ifdef __APPLE__
>> +HashValueImp(pthread_t, (size_t)data);
>> +#endif
>>   HashMap<pthread_t, std::pair<Log::ThreadSetting, bool> >
>> Log::mThreadToLevel;
>>   HashMap<int, std::set<pthread_t> > Log::mServiceToThreads;
>>   pthread_key_t* Log::mLevelKey = (Log::mLevelKey ? Log::mLevelKey :
>> new pthread_key_t);
>> Index: rutil/Log.hxx
>> ===================================================================
>> --- rutil/Log.hxx       (revision 7627)
>> +++ rutil/Log.hxx       (working copy)
>> @@ -21,7 +21,10 @@
>>   // crashes in the Mac OS native API.
>>   #if !defined(WIN32) && !defined(TARGET_OS_MAC)
>>   #define LOG_ENABLE_THREAD_SETTING
>> +#ifdef __APPLE__
>> +HashValue(pthread_t);
>>   #endif
>> +#endif
>>
>>   namespace resip
>>   {
>> Index: rutil/HashMap.hxx
>> ===================================================================
>> --- rutil/HashMap.hxx   (revision 7627)
>> +++ rutil/HashMap.hxx   (working copy)
>> @@ -10,21 +10,6 @@
>>   #    define HashMap __gnu_cxx::hash_map
>>   #    define HashSet __gnu_cxx::hash_set
>>
>> -// this allows us to hash on a pointer as the key
>> -namespace HASH_MAP_NAMESPACE
>> -{
>> -
>> -template <class T>
>> -struct hash<T*>
>> -{
>> -      size_t operator()(const T* t) const
>> -      {
>> -         return size_t(t);
>> -      }
>> -};
>> -
>> -}
>> -
>>   #define HashValue(type)                           \
>>   namespace HASH_MAP_NAMESPACE                      \
>>   {                                                 \
>>
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>