malloc crash

Mark Geisert
Mon Oct 25 23:36:50 GMT 2021

Ken Brown wrote:
> On 10/25/2021 5:29 PM, Mark Geisert wrote:
>> Corinna Vinschen wrote:
>>> On Oct 25 08:35, Ken Brown wrote:
>>>> On 10/25/2021 4:59 AM, Corinna Vinschen wrote:
>>>>> Has the thread already been started at this point?
>>>> Yes, here's the backtrace of that thread:
>>>> Thread 5 (Thread 9692.0x7c4c):
>>>> #0  0x00000001801934f9 in sys_alloc (m=0x18036f860 <_gm_>, nb=1040) at
>>>> ../../../../temp/winsup/cygwin/
>>>> #1  0x0000000180196b96 in dlmalloc (bytes=1024) at
>>>> ../../../../temp/winsup/cygwin/
>>>> #2  0x00000001801993e1 in dlrealloc (oldmem=0x0, bytes=1024) at
>>>> ../../../../temp/winsup/cygwin/
>>>> #3  0x00000001800e8eed in realloc (p=0x0, size=1024) at
>>>> ../../../../temp/winsup/cygwin/
>>> Er... huh?  So both threads are in a malloc function?  This shouldn't
>>> have happened, given the clunky muto guarding malloc calls.  This is
>>> really strange.  Why's the muto not working here?
>> Is it possible both threads have executed malloc_init()?
>> If so, the second one would reinit the muto.
> Or does the fifo_reader thread call a malloc function before the main thread has 
> called malloc_init()?  This would presumably cause __malloc_lock() to fail, but 
> there's no error check.

If there's a global constructor involved, that is known to happen.  Constructors 
are run from dll_crt0_0(), before malloc_init() is called from dll_crt0_1().  See for the details.


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