[avr-libc-dev] [bug #2143] malloc() routines chunk smaller than requested

[nobody]

=================== BUG #2143: LATEST MODIFICATIONS ==================
http://savannah.nongnu.org/bugs/?func=detailbug&bug_id=2143&group_id=2140

Changes by: Anonymous user        Date: Thu 07/10/03 at 10:09

------------------ Additional Follow-up Comments ----------------------------
malloc fails to detect that insufficient memory
is available if you allocate a block with length
larger than (unsigned)(0xffff) - brkval due to overflow
in the data types used.

doing it the quick way:
malloc()
{
unsigned long reqend;

/* ..... */

line 201:
        reqend = (unsigned long)(brkval) + (unsigned long)(len) + (unsigned 
long)(sizeof(size_t));

        if ( reqend < (unsigned long)(cp) ) {
/* ... */
        }

OR you could detect that brkval+len < len if you do want to keep
it somewhat independent of size_t being 16 bits (which doesn't 
seem to make sense on the AVR?).

Hope this helps

Regards
Titus





=================== BUG #2143: FULL BUG SNAPSHOT ===================


Submitted by: None                    Project: AVR C Runtime Library        
Submitted on: Mon 01/06/03 at 10:18
Category:  Library                    Severity:  5 - Major                  
Bug Group:  None                      Resolution:  None                     
Assigned to:  joerg_wunsch            Originator Email:  address@hidden    
Status:  Open                         

Summary:  malloc() routines chunk smaller than requested

Original Submission:  
I believe I've found in bug that exists in the malloc() implementation in the 
snapshots from 17dec2002 and 04nov2002.

Here's (basically) the code I'm running:

        char *ptrs[32];
        __malloc_heap_start = 0x8000;
        __malloc_heap_end = 0xFFFF;
        for (j = 0; j < 32; j++) {
                ptrs[j] = (char *)malloc(1024);
                /* output j and ptrs[j] to serial port */
        }

I would expect the last malloc() to return NULL, since there's not 1024 bytes 
left in the heap.  Instead, I get the following output:

0 = 00008002
1 = 00008404
2 = 00008806
-cut-
29 = 0000f43c
30 = 0000f83e
31 = 0000fc40

The last malloc() returns a chunk of memory that is only 959 bytes before the 
end of the heap!



Follow-up Comments
*******************

-------------------------------------------------------
Date: Thu 07/10/03 at 10:09         By: None
malloc fails to detect that insufficient memory
is available if you allocate a block with length
larger than (unsigned)(0xffff) - brkval due to overflow
in the data types used.

doing it the quick way:
malloc()
{
unsigned long reqend;

/* ..... */

line 201:
        reqend = (unsigned long)(brkval) + (unsigned long)(len) + (unsigned 
long)(sizeof(size_t));

        if ( reqend < (unsigned long)(cp) ) {
/* ... */
        }

OR you could detect that brkval+len < len if you do want to keep
it somewhat independent of size_t being 16 bits (which doesn't 
seem to make sense on the AVR?).

Hope this helps

Regards
Titus



-------------------------------------------------------
Date: Tue 02/25/03 at 06:19         By: None
creating a memmory heap malloc function writes some bytes of header information 
for handling heap size

-------------------------------------------------------
Date: Mon 01/06/03 at 17:02         By: joerg_wunsch
malloc() is my baby.


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