[Mono-dev] Malloc issue?

[Rodrigo Kumpera]

This crash is either a bug on glibc malloc, which I find to be the less
likely, or a bug on mono or your app.

Run it under the many malloc debugging tools that malloc(3) has or with a
tool such as valgrind - it will very
easily spot a memory overrun in mono/your app.

On Fri, Aug 24, 2012 at 11:12 AM, Greg Young <gregoryyoung1 at gmail.com>wrote:

> Will take a look. Not sure what it may not be liking. Code is very basic.
> Literally allocates 16mb chunk then frees it (each object has one) code
> works fine in windows with same calls. Will debug it on Sunday.
>
>
> On Friday, August 24, 2012, Jonathan Pryor wrote:
>
>> On Aug 23, 2012, at 2:35 AM, Greg Young <gregoryyoung1 at gmail.com> wrote:
>> > We are allocating and releasing unmanaged memory with
>> marshal.allochglobal. In mono we are getting the following failure (no
>> failures under clr).
>> >
>> > Any ideas?
>>
>> That's not a mono error, that's a glibc assert (and thus cannot become an
>> exception, ever):
>>
>> > part from team city logs:
>> > [20:55:52][Step 2/2] mono: malloc.c:2451: sYSMALLOc: Assertion
>> `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) -
>> __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) ||
>> ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof
>> (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 *
>> (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned
>> long)old_end & pagemask) == 0)' failed.
>>
>> Very probably coming from:
>>
>>
>> http://sourceware.org/git/?p=glibc.git;a=blob;f=malloc/malloc.c;h=0f1796c9134ffef289ec31fb1cd538f3a9490ae1;hb=HEAD#l2361
>>            /*
>>               If not the first time through, we require old_size to be
>>               at least MINSIZE and to have prev_inuse set.
>>            */
>>
>>            assert((old_top == initial_top(av) && old_size == 0) ||
>>                   ((unsigned long) (old_size) >= MINSIZE &&
>>                    prev_inuse(old_top) &&
>>                    ((unsigned long)old_end & pagemask) == 0));
>>
>> The line number is different, but it's the same file and the assert looks
>> close enough (considering macro expansion, etc.).
>>
>> In short, malloc(3) doesn't like you or something that you're doing. I
>> would suggest setting the MALLOC_CHECK_ environment variable (see the
>> malloc(3) man page), and/or "porting" your malloc use to C to verify that
>> it also crashes there.
>>
>>  - Jon
>>
>>
>
> --
> Le doute n'est pas une condition agréable, mais la certitude est absurde.
>
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