Shortest code that return SIGSEGV

Question

Shortest code that returns Segmentation Fault (SIGSEGV) in any programming language.

Answer 1

C, 5 characters

main;

It's variable declaration - int type is implied (feature copied from B language) and 0 is default value. When executed this tries to follow null pointer and causes SIGSEGV.

Answer 2

Bash, 11      

kill -11 $$

Answer 3

pdfTeX (51)

\def~#1{\meaning}\write0{\expandafter~\string}\bye

This is actually probably a bug, but it is not present in the original TeX, written by Knuth: compiling the code with tex filename.tex instead of pdftex filename.tex does not produce a segfault.

Answer 4

C, 18

main(){raise(11);}

Answer 5

3 Characters in Assembly

RET

writing only this will give Segmentation Fault.

Answer 6

Haskell, 31

foreign import ccall main::IO()

This produces a segfault when compiled with GHC and run. No extension flags are needed, as the Foreign Function Interface is in the Haskell 2010 standard.

Answer 7

C - 11(19) 7(15) 6(14) 1 chars, AT&T x86 assembler - 8(24) chars

C version is:

*(int*)0=0;

The whole program (not quite ISO-compliant, let's assume it's K&R C) is 19 chars long:

main(){*(int*)0=0;}

Assembler variant:

orl $0,0

The whole program is 24 chars long (just for evaluation, since it's not actually assembler):

main(){asm("orl $0,0");}

EDIT:

A couple of C variants. The first one uses zero-initialization of global pointer variable:

*p;main(){*p=0;}

The second one uses infinite recursion:

main(){main();}

The last variant is the shortest one - 7(15) characters.

EDIT 2:

Invented one more variant which is shorter than any of above - 6(14) chars. It assumes that literal strings are put into a read-only segment.

main(){*""=0;}

EDIT 3:

And my last try - 1 character long:

P

Just compile it like that:

cc -o segv -DP="main(){main();}" segv.c

Answer 8

Perl, 10 / 12 chars

A slightly cheatish solution is to shave one char off Joey Adams' bash trick:

kill 11,$$

However, to get a real segfault in Perl, unpack p is the obvious solution:

unpack p,1x8

Technically, this isn't guaranteed to segfault, since the address 0x31313131 (or 0x3131313131313131 on 64-bit systems) just might point to valid address space by chance. But the odds are against it. Also, if perl is ever ported to platforms where pointers are longer than 64 bits, the x8 will need to be increased.

Answer 9

C# - 62

System.Runtime.InteropServices.Marshal.ReadInt32(IntPtr.Zero);

Edit: 23

unsafe{int i=*(int*)0;}

Must compile with /unsafe for this one to work. For some reason I don't understand, *(int*)0=0 just throws a NullReferenceException, while this version gives the proper access violation.

Answer 10

19 characters in C

main(a){*(&a-1)=1;}

It corrupts return address value of main function, so it gets a SIGSEGV on return of main.

Answer 11

Python, 33 characters

>>> import ctypes;ctypes.string_at(0)
Segmentation fault

Source: http://bugs.python.org/issue1215#msg143236

Python, 60 characters

>>> import sys;sys.setrecursionlimit(1<<30);f=lambda f:f(f);f(f)
Segmentation fault

Source: http://svn.python.org/view/python/trunk/Lib/test/crashers/recursive_call.py?view=markup

This is the Python version I'm testing on:

Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin

In general the Python interpreter is hard to crash, but the above is selective abusiveness...

Answer 12

Python 33

import os
os.kill(os.getpid(),11)

Sending signal 11 (SIGSEGV) in python.

Answer 13

Perl ( < 5.14 ), 9 chars

/(?{??})/

In 5.14 the regex engine was made reentrant so that it could not be crashed in this way, but 5.12 and earlier will segfault if you try this.

Answer 14

dc - 7 chars

[dx0]dx

causes a stack overflow

Answer 15

Cython, 14

This often comes in handy for debugging purposes.

a=(<int*>0)[0]

Answer 16

F90 - 25 chars

REAL A(1)
n=2
A(n)=0
END

Compiled with Intel compiler 12.0 which actually refuses to compile without the intermediate n as it detects the bound error. Does this count as a segfault?:

ifort -C sigsegv.F90 
./a.out 
forrtl: severe (408): fort: (2): Subscript #1 of the array A has value 2 which is greater than the upper bound of 1