[PATCH] Fix memory leak in dtoa/ldtoa

[Joel Sherrill]

Hi,

This patch caused a side discussion among a few RTEMS folks. 
We don't have a concern about this patch but some general concerns
that I am asking about.

Balloc appears to correctly return NULL when calloc fails.
But I did see any Balloc caller check for a NULL being returned.
What should happen?

Is there a master list of things that cause memory allocation per thread
in newlib?  Eric Norum has an RTEMS test case which demonstrates
this leak for RTEMS applications and prints how much memory is available
after each thread create/delete.  We could enhance this to make the test 
thread
do the things that cause memory allocation to verify there isn't another 
leak.

--joel

Jeff Johnston wrote:
> Corinna Vinschen wrote:
>> Hi,
>>
>> the following report has been posted to the Cygwin list.  A test 
>> application
>> using printf("%f") in short-lived threads uses up all memory.  The test
>> application is very simple:
>>
>>   void *testThread(void *data)
>>   {
>>     printf("\r\n%f",1.232231212);
>>     return(NULL);
>>   }
>>   int main (int argc, char *argv[])
>>   {
>>     pthread_t t;
>>
>>     while(1)
>>       {
>>       pthread_create(&t,NULL,testThread,NULL);
>>       pthread_join(t,NULL);
>>       }     return 1;
>>   }
>> The cause is apparently a memory leak in ldtoa resp. dtoa.  The first
>> time the function is called, _REENT_MP_RESULT(ptr) gets newly allocated
>> memory by a call to Balloc.  This memory is Bfree'd in subsequent calls
>> to ldtoa/dtoa, but immediately re-Ballocated.  Since a Ballocated area
>> is only actually freed in _reclaim_reent when a matching Bfree has been
>> called, the _REENT_MP_RESULT(ptr) memory is never actually freed and
>> every new thread using ldtoa/dtoa will leak this memory area when the
>> thread exits.
>>
>> The solution is to explicitely free the _REENT_MP_RESULT(ptr) area in
>> _reclaim_reent.  That's what the below patch does.  Ok to apply?
>>
>
> Yes, please go ahead.  Thanks.
>
> -- Jeff J.
>
>>
>> Corinna
>>
>>
>>     * libc/reent/reeent.c (_reclaim_reent): Free _REENT_MP_RESULT.
>>
>>
>> Index: libc/reent/reent.c
>> ===================================================================
>> RCS file: /cvs/src/src/newlib/libc/reent/reent.c,v
>> retrieving revision 1.8
>> diff -u -p -r1.8 reent.c
>> --- libc/reent/reent.c    9 Sep 2004 19:46:54 -0000    1.8
>> +++ libc/reent/reent.c    9 Oct 2006 17:44:46 -0000
>> @@ -69,6 +69,8 @@ _DEFUN (_reclaim_reent, (ptr),
>>  
>>        _free_r (ptr, _REENT_MP_FREELIST(ptr));
>>      }
>> +      if (_REENT_MP_RESULT(ptr))
>> +        _free_r (ptr, _REENT_MP_RESULT(ptr));
>>  
>>  #ifdef _REENT_SMALL
>>        if (ptr->_emergency)
>>
>>
>