Re: Recursive SIGSEGV question

[Jonny Grant <jg@jguk.org>]

Hi!

On 25/03/2019 17:14, Florian Weimer wrote:
> * Andrew Haley:
> 
>> On 3/25/19 2:01 PM, Florian Weimer wrote:
>>> * Xi Ruoyao:
>>>
>>>> On 2019-03-25 13:06 +0000, Jonny Grant wrote:
>>>>>
>>>>> I built & ran with the Sanitizer, it seems it's also stack overflow
>>>>> within the operator new()
>>>>>
>>>>> I had thoughts GCC would generate code that monitored the stack size and
>>>>> aborted with a clear message when the stack size was exceeded. Looked
>>>>> online, and it doesn't seem to be the case.
>>>>
>>>> Impossible.  We can't distinguish "stack overflow" with other segmentation
>>>> faults.
>>>
>>> I think “impossible” is too strong.
>>
>> It is. We do it with stack banging and a few guard pages in the HotSpot JVM.
>> The problem is that recovering well enough to throw an exception requires
>> some quite hairy non-portable code.
> 
> Of course it's going to be non-portable.  Ideally, this would be
> handled out-of-process: the shell registers itself with the system
> coredump handler, and the handler analyzes the crash and provides
> information back to the shell for display.
> 
> It's quite difficult to get there, but it's certainly not impossible.
> We really should have lightweight tracebacks for aborts and the like
> in C/C++ code.  Right now, every moderately large piece of software
> tries to write their robust in-process crash handler, with varying
> results.
> .

Could GCC add a simple crash handler? maybe  -fcrash-handler

C++ exceptions show a few clues when there is a crash, which is helpful, eg:

// g++-8 -Wall -o cpp cpp.cpp
#include <vector>
int main()
{
     std::vector<int> v;
     return v.at(0);
}


$ ./cpp
terminate called after throwing an instance of 'std::out_of_range'
   what():  vector::_M_range_check: __n (which is 0) >= this->size() 
(which is 0)
Aborted


Jonny