Error

[sundar divas]

Program received signal SIGSEGV, Segmentation fault.
0xff2209e8 in _write () from /usr/lib/libc.so.1
(gdb) up
#1 0xff212bf4 in _xflsbuf () from /usr/lib/libc.so.1
(gdb) up
#2 0xff21000c in _flsbuf () from /usr/lib/libc.so.1
(gdb) up
#3 0x00000037 in ?? ()
(gdb) up
#4 0x00000037 in ?? ()
(gdb) up
Previous frame identical to this frame (corrupt stack?)
(gdb) up
Initial frame selected; you cannot go up.
(gdb)

Any help?

[sundar divas]

It is actually crazy. I have a call to a recursive function process() which recursively calls itself for 22460 times, but after taht it executes exactly the first line inside process which is cout<<"hi"; after which it says seg. fault and shows the above error. If I type another cout<"hi"; again after that, it executes the first cout and gives a seg fault. I mean it exactly executes the first line in the function and gives a seg. fault immediatley. I wonder what's happening

[Ancient Dragon]

what's happening is called stack overflow. Each recursive call required a little more stack space (or a lot more depending on how you wrote the function). Try to figure out how much stack space the function needs, add about 8 bytes for return address then multiply that by 22460. That could be a huge amount of memory.

[sundar divas]

How to figure out how much stack space the function needs

How to add 8 bytes for return address then multiply that by 22460

I am new to C++ programming and dont have much idea. Can you give me an example or something

[thekashyap]

google for getrusage, here is one link.

[Salem]

It's just simple maths

void process ( int a, int b ) {
  char var[10];
  process( 0, 0 );
}

You have a char array, so that's 10 bytes.
Two integers - say 4 bytes each (total 8).
Each call has a fixed overhead of several bytes (say saving the return address of the call), another 8.

So that's 26 bytes in this example.
26 * 22460 = 583960
which is way over 1/2MB.

Consider that many systems limit the stack space to a few MB in total anyway, then you don't need too many more local variables before you're in deep trouble.

The first thing you should do is look for a non-recursive solution (there is always a non-recursive solution).

[sundar divas]

I actaully tried calling non recursively and it works. I tried calling the function non-recursively more than 4 or 5 times and it still works. But for recursive function as I mentioned it loops for around 22460 times after which it seg. faults. By anyway can I find which line wrong memory allocation is taking place?

[thekashyap]

You can also find out the limits using getrlimit. So check if you're going over it or not.

[vijayan121]

It's just simple maths

void process ( int a, int b ) {
  char var[10];
  process( 0, 0 );
}

You have a char array, so that's 10 bytes.
Two integers - say 4 bytes each (total 8).
Each call has a fixed overhead of several bytes (say saving the return address of the call), another 8.

So that's 26 bytes in this example.
26 * 22460 = 583960...

we need to also take into acount
a. padding that would be added to align data (eg. in the above example, 2 bytes for the char array in a 32 bit architecture).
b. many compilers would also insert canaries on the stack to enable stack smashing protection. microsoft c++ 8, icc 9, gcc on FreeBSD, NetBsd, OpenBSD and SystemX all implement canaries by default. these canaries would be there in every stack frame (see http://en.wikipedia.org/wiki/Stack-smashing_protection#Implementations )