Re: Recursive SIGSEGV question

[Xi Ruoyao <xry111@mengyan1223.wang>]

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.
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University