malloc crash

[Mark Geisert]

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/malloc.cc:4232
>>>> #1  0x0000000180196b96 in dlmalloc (bytes=1024) at
>>>> ../../../../temp/winsup/cygwin/malloc.cc:4669
>>>> #2  0x00000001801993e1 in dlrealloc (oldmem=0x0, bytes=1024) at
>>>> ../../../../temp/winsup/cygwin/malloc.cc:5187
>>>> #3  0x00000001800e8eed in realloc (p=0x0, size=1024) at
>>>> ../../../../temp/winsup/cygwin/malloc_wrapper.cc:73
>>>
>>> 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 
dcrt0.cc for the details.

..mark