Re: Recursive SIGSEGV question

[Jonny Grant <jg@jguk.org>]

Hi!

On 25/03/2019 13:55, Xi Ruoyao wrote:
> 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.  For example
> 
> int foo() {volatile char p[10000000]; p[0] = 1;}
> 
> and
> 
> int foo() {
>   volatile char a;
>   (&a)[-9999999] = 1;
> }
> 
> may be compiled to exactly same machine code.  Now which one is a stack
> overflow?
> 
>> AddressSanitizer:DEADLYSIGNAL
>> =================================================================
>> ==16598==ERROR: AddressSanitizer: stack-overflow on address
>> 0x7ffe4b0e7fc0 (pc 0x7f85c609293a bp 0x7ffe4b0e88d0 sp 0x7ffe4b0e7fb0 T0)
>>       #0 0x7f85c6092939  (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x28939)
>>       #1 0x7f85c6091217  (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x27217)
>>       #2 0x7f85c615974e in operator new(unsigned long)
>> (/usr/lib/x86_64-linux-gnu/libasan.so.5+0xef74e)
>>       #3 0x563e23701a4a in void std::__cxx11::basic_string<char,
>> std::char_traits<char>, std::allocator<char> >::_M_construct<char
>> const*>(char const*, char const*, std::forward_iterator_tag)
>> /usr/include/c++/8/bits/basic_string.tcc:219
>>       #4 0x563e23947131 in void std::__cxx11::basic_string<char,
>> std::char_traits<char>, std::allocator<char> >::_M_construct_aux<char
>> const*>(char const*, char const*, std::__false_type)
>> /usr/include/c++/8/bits/basic_string.h:236
>>       #5 0x563e23947131 in void std::__cxx11::basic_string<char,
>> std::char_traits<char>, std::allocator<char> >::_M_construct<char
>> const*>(char const*, char const*) /usr/include/c++/8/bits/basic_string.h:255
>>       #6 0x563e23947131 in std::__cxx11::basic_string<char,
>> std::char_traits<char>, std::allocator<char> >::basic_string(char
>> const*, std::allocator<char> const&)
>> /usr/include/c++/8/bits/basic_string.h:516
> 
> If you consume too much stack, stack overflow may happens in any functions.  For
> example:
> 
> int x()
> {
> 	int a[100];
> 	malloc(1);
> 	return x();
> }
> 
> int main()
> {
> 	return x();
> }
> 
>> Sanitizer says the same. There isn't really anything that can be done
>> when stack is exceeded! There isn't a StackOverflowException
> 
> This is gcc-help, not java-help or python-help.  But actually you can do
> something here:
> 
> 0.  Do not consume so much stack.  Throw large things into the heap.
> 1.  Set a signal handler for SIGSEGV.  And you will need sigaltstack so the
> signal handler can run in an alternative stack.
> 2.  Use ulimit -s or setrlimit to increase stack limit, if you really need more
> stack.
> 3.  Use -fsplit-stack to automatically "increase" stack size when it overflows,
> if you really need this feature.
> 
> If you don't like all of these suggestions, go to use Java.
> 

Sorry, it looks like there was a misunderstanding. I don't need more 
stack. Testcase was created to recurse and reproduce crash! It 
replicated a typo in an application change, which called itself !

The compiler toolchain is ideally placed to provide a clearer abort, 
exit, backtrace when such issues occur. Feels like this mailing list is 
the ideal place to discuss.

Jonny