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Revision as of 19:00, 4 October 2020
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Find the limit of recursion.
8080 Assembly
The 8080 was the first Intel processor to support a stack in RAM. (Its predecessor, the 8008, had an on-die call stack that was limited to 7 levels.) This means it was the first one on which recursive calls could be somewhat practical. It also set the convention that the machine stack grows downward into memory (i.e., the topmost item on the stack is one word below the second one, etc.), which is still true on modern Intel processors.
However, it has no support for any kind of memory protection. If the stack grows too large, it will simply overwrite other data or code, and the program will crash. This means it is up to the programmer to take care that this does not happen. Below are two ways of finding out the maximum recursion limit without crashing the program. (Note that they will give slightly different answers on the same system, as one program is slightly bigger than the other, leaving a little less room for the stack.)
Using a stack guard
One way of doing this is by using a stack guard (also known as a stack sentinel). The technique is to store a word of data just beyond the last byte of memory that the program wants to use. When you do a recursive call, you first check if it is still intact. If it isn't, the next call will overwrite something important, so in that case, the stack is full. This way, a stack overflow can be caught at run-time, at the cost of some overhead per call.
<lang 8080asm> org 100h lxi b,0 ; BC holds the amount of calls call recur ; Call the recursive routine ;;; BC now holds the maximum amount of recursive calls one ;;; can make, and the stack is back to the beginning. ;;; Print the value in BC to the console. The stack is freed by ret ;;; so push and pop can be used. ;;; Make number into ASCII string lxi h,num push h mov h,b mov l,c lxi b,-10 dgt: lxi d,-1 clcdgt: inx d dad b jc clcdgt mov a,l adi 10+'0' xthl dcx h mov m,a xthl xchg mov a,h ora l jnz dgt ;;; Use CP/M routine to print the string pop d mvi c,9 call 5 rst 0 ;;; Recursive routine recur: inx b ; Count the call lxi d,-GUARD ; See if the guard is intact (stack not full) lhld guard ; (subtract the original value from the dad d ; current one) mov a,h ; If so, the answer should be zero ora l cz recur ; If it is, do another recursive call ret ; Return ;;; Placeholder for numeric output db '00000' num: db '$' ;;; The program doesn't need any memory after this location, ;;; so all memory beyond here is free for use by the stack. ;;; If the guard is overwritten, the stack has overflowed. GUARD: equ $+2 ; Make sure it is not a valid return address guard: dw GUARD</lang>
- Output:
27034
(Value will differ depending on system, CP/M version, memory size, etc.)
Calculating the value
If all you need to know is how much room there is beforehand, it's possible to
just calculate the value. The 8080 processor decides where the stack is depending
on the SP (stack pointer) register, which always points to the
location of the topmost stack item (or, if the stack is considered 'empty',
it is just outside the stack).
Therefore, if you take the address of the highest byte of memory that your
program is actually using, and subtract this from SP, you get the
amount of free stack memory, in bytes. Because a stack item is two bytes
(addresses are 16 bits), if you then divide it by 2, you get the maximum amount
of calls you can make before the stack is full (and would overwrite your program).
<lang 8080asm> org 100h lxi h,-top ; Subtract highest used location from stack pointer dad sp xra a ; This gives bytes, but a call takes two bytes; ora h ; so HL should be divided by two to give the actual rar ; number. mov h,a mov a,l rar mov l,a ;;; The number of free stack words is now in HL, output it lxi d,num push d lxi b,-10 dgt: lxi d,-1 clcdgt: inx d dad b jc clcdgt mov a,l adi 10+'0' xthl dcx h mov m,a xthl xchg mov a,h ora l jnz dgt ;;; Use CP/M routine to print the string pop d mvi c,9 call 5 rst 0 ;;; Placeholder for numeric output db '00000' num: db '$' ;;; The program does not need any memory beyond this point. ;;; This means anything from this place up to SP is free for the ;;; stack. top: equ $ </lang>
- Output:
27039
(Value will differ depending on system, CP/M version, memory size, etc.)
ACL2
<lang Lisp>(defun recursion-limit (x)
(if (zp x)
0
(prog2$ (cw "~x0~%" x)
(1+ (recursion-limit (1+ x))))))</lang>
- Output:
(trimmed)
87195 87196 87197 87198 87199 87200 87201 *********************************************** ************ ABORTING from raw Lisp *********** Error: Stack overflow on value stack. ***********************************************
Ada
<lang Ada>with Ada.Text_IO; use Ada.Text_IO;
procedure Test_Recursion_Depth is
function Recursion (Depth : Positive) return Positive is
begin
return Recursion (Depth + 1);
exception
when Storage_Error =>
return Depth;
end Recursion;
begin
Put_Line ("Recursion depth on this system is" & Integer'Image (Recursion (1)));
end Test_Recursion_Depth;</lang> Note that unlike some solutions in other languages this one does not crash (though usefulness of this task is doubtful).
In Ada Storage_Error exception is propagated when there is no free memory to accomplish the requested action. In particular it is propagated upon stack overflow within the task where this occurs. Storage_Error can be handled without termination of the task. In the solution the function Recursion calls itself or else catches Storage_Error indicating stack overflow.
Note that this technique requires some care, because there must be enough stack space for the handler to work. In this case it works because the handler just return the current call depth. In real-life Storage_Error is usually fatal.
- Output:
Recursion depth on this system is 524091
ALGOL 68
The depth of recursion in Algol 68 proper is unlimited. Particular implementations will reach a limit, if only through exhaustion of storage and/or address space and/or time before power failure. If not time limited, the depth reached depends very much on what the recursive routine needs to store on the stack, including local variables if any. The simplest recursive Algol68 program is: <lang algol68>PROC recurse = VOID : recurse; recurse</lang> This one-liner running under Algol68 Genie and 64-bit Linux reaches a depth of 3535 with the shell's default stack size of 8Mbytes and 28672 when set to 64Mbytes, as shown by the following output. From this we can deduce that Genie does not implement tail recursion. The --trace option to a68g prints a stack trace when the program crashes; the first two commands indicate the format of the trace, the third counts the depth of recursion with the default stack size and the fourth shows the result of octupling the size of the stack.
- Output:
pcl@anubis ~/a68/Rosetta $ a68g --trace Recurse.a68 | head
genie: frame stack 6144k, expression stack 2048k, heap 49152k, handles 8192k
BEGIN MODE DOUBLE = LONG REAL, QUAD = LONG LONG REAL;
-
1 PROC recurse = VOID : recurse; recurse
-
genie_unit
1 PROC recurse = VOID : recurse; recurse
-
genie_unit
1 PROC recurse = VOID : recurse; recurse
pcl@anubis ~/a68/Rosetta $ a68g --trace Recurse.a68 | tail
1 PROC recurse = VOID : recurse; recurse
-
genie_unit
1 PROC recurse = VOID : recurse; recurse
-
genie_unit
1 PROC recurse = VOID : recurse; recurse
1
a68g: runtime error: 1: stack overflow (detected in particular-program).
Genie finished in 0.19 seconds
pcl@anubis ~/a68/Rosetta $ a68g --trace Recurse.a68 | grep recurse | wc
3535 28280 159075
pcl@anubis ~/a68/Rosetta $ prlimit --stack=67108864 a68g --trace Recurse.a68 | grep recurse | wc
28672 229376 1290240
pcl@anubis ~/a68/Rosetta $
AppleScript
A basic test for Applescript, which has a notoriously shallow recursion stack. <lang applescript>-- recursionDepth :: () -> IO String on recursionDepth()
script go
on |λ|(i)
try
|λ|(1 + i)
on error
"Recursion limit encountered at " & i
end try
end |λ|
end script
go's |λ|(0)
end recursionDepth
on run
recursionDepth()
end run</lang>
- Output:
"Recursion limit encountered at 502"
We get a fractionally higher (and arguably purer) result by deriving the highest Church Numeral (Church-encoded integer) that can be represented using AppleScript: <lang applescript>-- HIGHEST CHURCH NUMERAL REPRESENTABLE IN APPLESCRIPT ?
-- (This should be a good proxy for recursion depth)
on run
script unrepresentable
on |λ|(x)
try
churchFromInt(x)
return false
on error
return true
end try
x > 10
end |λ|
end script
"The highest Church-encoded integer representable in Applescript is " & ¬
(|until|(unrepresentable, my succ, 0) - 1)
end run
-- CHURCH NUMERALS ------------------------------------------------------
-- chZero :: (a -> a) -> a -> a on chZero(f)
script
on |λ|(x)
x
end |λ|
end script
end chZero
-- chSucc :: ((a -> a) -> a -> a) -> (a -> a) -> a -> a on chSucc(n)
script
on |λ|(f)
script
property mf : mReturn(f)'s |λ|
on |λ|(x)
mf(mReturn(n)'s |λ|(mf)'s |λ|(x))
end |λ|
end script
end |λ|
end script
end chSucc
-- churchFromInt :: Int -> (a -> a) -> a -> a on churchFromInt(x)
script go
on |λ|(i)
if 0 < i then
chSucc(|λ|(i - 1))
else
chZero
end if
end |λ|
end script
go's |λ|(x)
end churchFromInt
-- intFromChurch :: ((Int -> Int) -> Int -> Int) -> Int on intFromChurch(cn)
mReturn(cn)'s |λ|(my succ)'s |λ|(0)
end intFromChurch
-- GENERIC FUNCTIONS ----------------------------------------
-- until :: (a -> Bool) -> (a -> a) -> a -> a on |until|(p, f, x)
set v to x
set mp to mReturn(p)
set mf to mReturn(f)
repeat until mp's |λ|(v)
set v to mf's |λ|(v)
end repeat
end |until|
-- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: First-class m => (a -> b) -> m (a -> b) on mReturn(f)
if class of f is script then
f
else
script
property |λ| : f
end script
end if
end mReturn
-- succ :: Enum a => a -> a on succ(x)
1 + x
end succ</lang>
- Output:
"The highest Church-encoded integer representable in Applescript is 571"
AutoHotkey
<lang AutoHotkey>Recurse(0)
Recurse(x) {
TrayTip, Number, %x% Recurse(x+1)
}</lang>
Last visible number is 827.
AutoIt
<lang AutoIt>;AutoIt Version: 3.2.10.0 $depth=0 recurse($depth) Func recurse($depth)
ConsoleWrite($depth&@CRLF) Return recurse($depth+1)
EndFunc</lang> Last value of $depth is 5099 before error. Error: Recursion level has been exceeded - AutoIt will quit to prevent stack overflow.
AWK
<lang AWK># syntax: GAWK -f FIND_LIMIT_OF_RECURSION.AWK
- version depth messages
- ------------------ ----- --------
- GAWK 3.1.4 2892 none
- XML GAWK 3.1.4 3026 none
- GAWK 4.0 >999999
- MAWK 1.3.3 4976 A stack overflow was encountered at
- address 0x7c91224e.
- TAWK-DOS AWK 5.0c 357 stack overflow
- TAWK-WIN AWKW 5.0c 2477 awk stack overflow
- NAWK 20100523 4351 Segmentation fault (core dumped)
BEGIN {
x()
print("done")
} function x() {
print(++n)
if (n > 999999) { return }
x()
}</lang>
Axe
Warning: running this program will cause you to have to clear your RAM. You will lose any data stored in RAM.
In Axe 1.2.2 on a TI-84 Plus Silver Edition, the last line this prints before hanging is 12520. This should be independent of any arguments passed since they are not stored on the stack.
<lang axe>RECURSE(1) Lbl RECURSE .Optionally, limit the number of times the argument is printed Disp r₁▶Dec,i RECURSE(r₁+1)</lang>
BASIC
Applesoft BASIC
Each GOSUB consumes 6 bytes of stack space and when more than 25 levels have been reached and an ?OUT OF MEMORY ERROR message is displayed.
<lang ApplesoftBasic> 100 PRINT "RECURSION DEPTH"
110 PRINT D" "; 120 LET D = D + 1 130 GOSUB 110"RECURSION</lang>
- Output:
RECURSION DEPTH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 ?OUT OF MEMORY ERROR IN 120
BaCon
Utterly dependent on the stack size and RAM available to the process.
<lang freebasic>' Recursion limit FUNCTION recurse(i)
PRINT i extraneous = recurse(i+1) RETURN 0
END FUNCTION
extraneous = recurse(0)</lang>
- Output:
prompt$ ./recursion-limit 0 1 2 ... 261881 261882 261883 Segmentation fault
FreeBASIC
<lang freebasic>sub sisyphus( n as ulongint )
print n sisyphus( 1 + n )
end sub sisyphus(0)</lang>
- Output:
0 1 2 ... 261785 261786 261787 Segmentation fault (core dumped)
Sinclair ZX81 BASIC
The only limit is the available memory. <lang basic>10 LET D=0 20 GOSUB 30 30 PRINT AT 0,0;D 40 LET D=D+1 50 GOSUB 30</lang>
- Output:
Run with 1k of RAM:
345 4/30
(The error code means "out of memory attempting to execute line 30".)
ZX Spectrum Basic
On the ZX Spectrum recursion is limited only by stack space. The program eventually fails, because the stack is so full that there is no stack space left to make the addition at line 110: <lang zxbasic>10 LET d=0: REM depth 100 PRINT AT 1,1; "Recursion depth: ";d 110 LET d=d+1 120 GO SUB 100: REM recursion 130 RETURN: REM this is never reached 200 STOP</lang>
- Output:
(from a 48k Spectrum)
Recursion depth: 13792 4 Out of memory, 110:1
Batch File
MUNG.CMD is a commandline tool written in DOS Batch language. It finds the limit of recursion possible using CMD /C.
<lang dos>@echo off set /a c=c+1 echo [Depth %c%] Mung until no good cmd /c mung.cmd echo [Depth %c%] No good set /a c=c-1</lang>
Result (abbreviated):
... [Depth 259] Mung until no good [Depth 260] Mung until no good [Depth 261] Mung until no good [Depth 261] No good [Depth 260] No good [Depth 259] No good ...
If one uses call rather than CMD/C, the call depth is much deeper but ends abruptly and can't be trapped.
<lang dos>@echo off set /a c=c+1 echo [Depth %c%] Mung until no good call mung.cmd echo [Depth %c%] No good set /a c=c-1</lang>
Result (abbreviated):
1240: Mung until no good 1241: Mung until no good ****** B A T C H R E C U R S I O N exceeds STACK limits ****** Recursion Count=1240, Stack Usage=90 percent ****** B A T C H PROCESSING IS A B O R T E D ******
You also get the exact same results when calling mung internally, as below
<lang dos>@echo off set c=0
- mung
set /a c=c+1 echo [Level %c%] Mung until no good call :mung set /a c=c-1 echo [Level %c%] No good</lang>
Setting a limit on the recursion depth can be done like this:
<lang dos>@echo off set c=0
- mung
set /a c=%1+1 if %c%==10 goto :eof echo [Level %c%] Mung until no good call :mung %c% set /a c=%1-1 echo [Level %c%] No good</lang>
BBC BASIC
<lang bbcbasic> PROCrecurse(1)
END
DEF PROCrecurse(depth%)
IF depth% MOD 100 = 0 PRINT TAB(0,0) depth%;
PROCrecurse(depth% + 1)
ENDPROC</lang>
- Output:
from BBC BASIC for Windows with default value of HIMEM
37400 No room
Befunge
In Befunge, the limit of recursion is essentially the depth of the stack. The program below calculates that limit by repeatedly pushing values until the stack overflows. After every iteration, it writes out the count of values pushed so far, so once the stack eventually does overflow, the last value output should tell you the depth that was reached.
Most interpreters allocate their stack on the global heap, so the size of the stack will depend on available memory, and on a modern system you're likely to run out of patience long before you run out of memory. That said, there have been some interpreters with a fixed stack depth - as low as 199 even - but that isn't a common implementation choice.
<lang befunge>1>1#:+#.:_@</lang>
Bracmat
<lang bracmat>rec=.out$!arg&rec$(!arg+1)</lang>
Observed recursion depths:
Windows XP command prompt: 6588 Linux: 18276
Bracmat crashes when it tries to exceed the maximum recursion depth.
C
<lang c>#include <stdio.h>
void recurse(unsigned int i) {
printf("%d\n", i);
recurse(i+1); // 523756
}
int main() {
recurse(0); return 0;
}</lang>
Segmentation fault occurs when i is 523756.
(This was checked debugging with gdb rather than waiting the output:
the printf line for the test was commented).
It must be noted that the recursion limit depends on how many parameters are passed onto the stack.
E.g. adding a fake double argument to recurse, the limit is reached at i == 261803.
The limit depends on the stack size and usage in the function.
Even if there are no arguments, the return address for a call to a subroutine is stored on the stack (at least on x86 and many more processors), so this is consumed even if we put arguments into registers.
The following code may have some effect unexpected by the unwary: <lang C>#include <stdio.h>
char * base; void get_diff() { char x; if (base - &x < 200) printf("%p %d\n", &x, base - &x); }
void recur() { get_diff(); recur(); }
int main()
{
char v = 32;
printf("pos of v: %p\n", base = &v);
recur();
return 0;
}</lang>
With GCC 4.5, if compiled without -O2, it segfaults quickly; if gcc -O2, crash never happens, because the optimizer noticed the tail recursion in recur() and turned it into a loop!
C#
<lang csharp>using System; class RecursionLimit {
static void Main(string[] args)
{
Recur(0);
}
private static void Recur(int i)
{
Console.WriteLine(i);
Recur(i + 1);
}
}</lang>
Through debugging, the highest I achieve is 14250.
Through execution (with Mono), another user has reached 697186.
C++
<lang cpp>
- include <iostream>
void recurse(unsigned int i) {
std::cout<<i<<"\n"; recurse(i+1);
}
int main() {
recurse(0);
} </lang>
Clojure
<lang clojure> => (def *stack* 0) => ((fn overflow [] ((def *stack* (inc *stack*))(overflow)))) java.lang.StackOverflowError (NO_SOURCE_FILE:0) => *stack* 10498 </lang>
COBOL
<lang cobol>identification division. program-id. recurse. data division. working-storage section. 01 depth-counter pic 9(3). 01 install-address usage is procedure-pointer. 01 install-flag pic x comp-x value 0. 01 status-code pic x(2) comp-5. 01 ind pic s9(9) comp-5.
linkage section.
01 err-msg pic x(325).
procedure division. 100-main.
set install-address to entry "300-err".
call "CBL_ERROR_PROC" using install-flag install-address returning status-code.
if status-code not = 0 display "ERROR INSTALLING ERROR PROC" stop run
end-if
move 0 to depth-counter.
display 'Mung until no good.'. perform 200-mung. display 'No good.'. stop run.
200-mung. add 1 to depth-counter. display depth-counter. perform 200-mung. 300-err. entry "300-err" using err-msg. perform varying ind from 1 by 1 until (err-msg(ind:1) = x"00") or (ind = length of err-msg) continue end-perform
display err-msg(1:ind).
- > room for a better-than-abrupt death here.
exit program.</lang>
Compiled with
cobc -free -x -g recurse.cbl
gives, after a while,
... 249 250 251 252 253 Trapped: recurse.cob:38: Stack overflow, possible PERFORM depth exceeded recurse.cob:50: libcob: Stack overflow, possible PERFORM depth exceeded
Without stack-checking turned on (achieved with -g in this case), it gives
... 249 250 251 252 253 254 255 256 257 Attempt to reference unallocated memory (Signal SIGSEGV) Abnormal termination - File contents may be incorrect
which suggests that -g influences the functionality of CBL_ERROR_PROC
Thanks to Brian Tiffin for his demo code on opencobol.org's forum
A more 'canonical' way of doing it
from Richard Plinston on comp.lang.cobol
<lang cobol> IDENTIFICATION DIVISION.
PROGRAM-ID. recurse RECURSIVE.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 Starter PIC S9(8) VALUE 1.
PROCEDURE DIVISION.
Program-Recurse.
CALL "recurse-sub" USING Starter
STOP RUN.
IDENTIFICATION DIVISION.
PROGRAM-ID. recurse-sub.
DATA DIVISION.
WORKING-STORAGE SECTION.
LINKAGE SECTION.
01 Countr PIC S9(8).
PROCEDURE DIVISION USING Countr.
Program-Recursive.
DISPLAY Countr
ADD 1 TO Countr
CALL "recurse-sub" USING Countr
EXIT PROGRAM.
END PROGRAM recurse-sub.
END PROGRAM recurse. </lang>
Compiled with
cobc -x -g recurse.cbl
gives
... +00000959 +00000960 +00000961 +00000962 +00000963 +00000964 recurse.cbl:19: Attempt to reference unallocated memory (Signal SIGSEGV) Abnormal termination - File contents may be incorrect
CoffeeScript
<lang coffeescript> recurse = ( depth = 0 ) ->
try
recurse depth + 1
catch exception
depth
console.log "Recursion depth on this system is #{ do recurse }" </lang>
- Output:
Example on Node.js
Recursion depth on this system is 9668
Common Lisp
<lang lisp> (defun recurse () (recurse)) (trace recurse) (recurse) </lang>
- Output:
This test was done with clisp under cygwin
3056. Trace: (RECURSE) 3057. Trace: (RECURSE) 3058. Trace: (RECURSE) 3059. Trace: (RECURSE) *** - Lisp stack overflow. RESET
However, for an implementation of Lisp that supports proper tail recursion, this function will not cause a stack overflow, so this method will not work.
D
<lang d>import std.c.stdio;
void recurse(in uint i=0) {
printf("%u ", i);
recurse(i + 1);
}
void main() {
recurse();
}</lang> With the DMD compiler, using default compilation arguments, the stack overflows at 51_002.
With DMD increasing the stack size using for example -L/STACK:1500000000 the stack overflows at 75_002_026.
Using -O compilation argument DMD performs tail call optimization, and the stack doesn't overflow.
Dc
Tail recursion is optimized into iteration by GNU dc, so I designed a not tail recursive function, summing all numbers up to n: <lang dc>## f(n) = (n < 1) ? n : f(n-1) + n; [q]sg [dSn d1[>g 1- lfx]x Ln+]sf [ [n=]Pdn []pP lfx [--> ]P p ]sh
65400 lhx 65600 lhx</lang> With the standard Ubuntu stack size limit 8MB I get
- Output:
$ time dc t1.dc n=65400 --> 2138612700 n=65600 Segmentation fault (core dumped) real 0m0.337s user 0m0.112s sys 0m0.008s
With larger stack size limit I get linearly greater numbers: stack size / 128.
Delphi
<lang delphi>program Project2; {$APPTYPE CONSOLE} uses
SysUtils;
function Recursive(Level : Integer) : Integer; begin
try
Level := Level + 1;
Result := Recursive(Level);
except
on E: EStackOverflow do
Result := Level;
end;
end;
begin
Writeln('Recursion Level is ', Recursive(0));
Writeln('Press any key to Exit');
Readln;
end.</lang>
- Output:
Recursion Level is 28781
DWScript
Recursion limit is a parameter of script execution, which can be specified independently from the stack size to limit execution complexity.
<lang delphi>var level : Integer;
procedure Recursive; begin
Inc(level);
try
Recursive;
except
end;
end;
Recursive;
Println('Recursion Level is ' + IntToStr(level));</lang>
Déjà Vu
<lang dejavu>rec-fun n:
!. n
rec-fun ++ n
rec-fun 0</lang>
This continues until the memory is full, so I didn't wait for it to finish.
Currently, it should to to almost 3 million levels of recursion on a machine with 1 GB free.
Eliminating the n should give over 10 million levels on the same machine.
E
Outside of debugging access to other vats, E programs are (ideally) not allowed to observe recursion limits, because stack unwinding at an arbitrary point can break invariants of the code that was executing at the time. In particular, consider an attacker who estimates the stack size, nearly fills up the stack to that point, then invokes the victim — If the attacker is allowed to catch our hypothetical StackOverflowException from inside the victim, then there is a good chance of the victim then being in an inconsistent state, which the attacker can then make use of.
EasyLang
<lang>func recurse i . .
print i call recurse i + 1
. call recurse 0</lang>
0 . . 9999 ---------------------------- | max call depth of exceeded | ----------------------------
Elixir
same as "Erlang"
Emacs Lisp
<lang lisp>(defun my-recurse (n)
(my-recurse (1+ n)))
(my-recurse 1) => enters debugger at (my-recurse 595), per the default max-lisp-eval-depth 600 in Emacs 24.1</lang>
Variable max-lisp-eval-depth[1] is the maximum depth of function calls and variable max-specpdl-size[2] is the maximum depth of nested let bindings. A function call is a let of the parameters, even if there's no parameters, and so counts towards max-specpdl-size as well as max-lisp-eval-depth.
The limits can be increased with setq etc globally, or let etc temporarily. Lisp code which knows it needs deep recursion might temporarily increase the limits. Eg. regexp-opt.el. The ultimate limit is memory or C stack.
Erlang
Erlang has no recursion limit. It is tail call optimised. If the recursive call is not a tail call it is limited by available RAM. Please add what to save on the stack and how much RAM to give to Erlang and I will test that limit.
F#
A tail-recursive function will run indefinitely without problems (the integer will overflow, though).
<lang fsharp>let rec recurse n =
recurse (n+1)
recurse 0</lang>
The non-tail recursive function of the following example crashed with a StackOverflowException after 39958 recursive calls:
<lang fsharp>let rec recurse n =
printfn "%d" n 1 + recurse (n+1)
recurse 0 |> ignore</lang>
Factor
Factor is tail-call optimized, so the following example will run without issue. In fact, Factor's iterative combinators such as map, each, and times are written in terms of tail recursion.
<lang factor>: recurse ( n -- n ) 1 + recurse ;
0 recurse</lang> The following non-tail recursive word caused a call stack overflow error after 65518 recursive calls in the listener. <lang factor>SYMBOL: depth
- fn ( n -- n ) depth inc 1 + fn 1 + ;
[ 0 fn ] try depth get "Recursion depth on this system is %d.\n" printf</lang>
- Output:
Call stack overflow Type :help for debugging help. Recursion depth on this system is 65518.
Forth
<lang forth>: munge ( n -- n' ) 1+ recurse ;
- test 0 ['] munge catch if ." Recursion limit at depth " . then ;
test \ Default gforth: Recursion limit at depth 3817</lang>
Or you can just ask the system:
<lang forth>s" return-stack-cells" environment? ( 0 | potential-depth-of-return-stack -1 )</lang>
Full TCO is problematic, but a properly tail-recursive call is easy to add to any Forth. For example, in SwiftForth:
<lang forth>: recur; [ last 2 cells + literal ] @ +bal postpone again ; immediate
- test dup if 1+ recur; then drop ." I gave up finding a limit!" ;
1 test</lang>
Fortran
<lang fortran>program recursion_depth
implicit none
call recurse (1)
contains
recursive subroutine recurse (i)
implicit none integer, intent (in) :: i
write (*, '(i0)') i call recurse (i + 1)
end subroutine recurse
end program recursion_depth</lang>
- Output:
(snipped)
208914 208915 208916 208917 208918 208919 208920 208921 208922 208923 Segmentation fault (core dumped)
GAP
The limit is around 5000 : <lang gap>f := function(n)
return f(n+1);
end;
- Now loop until an error occurs
f(0);
- Error message :
- Entering break read-eval-print loop ...
- you can 'quit;' to quit to outer loop, or
- you may 'return;' to continue
n;
- 4998
- quit "brk mode" and return to GAP
quit;</lang> This is the default GAP recursion trap, see reference manual, section 7.10. It enters "brk mode" after multiples of 5000 recursions levels. On can change this interval : <lang gap>SetRecursionTrapInterval(100000);
- No limit (may crash GAP if recursion is not controlled) :
SetRecursionTrapInterval(0);</lang>
gnuplot
<lang gnuplot># Put this in a file foo.gnuplot and run as
- gnuplot foo.gnuplot
- probe by 1 up to 1000, then by 1% increases
if (! exists("try")) { try=0 } try=(try<1000 ? try+1 : try*1.01)
recurse(n) = (n > 0 ? recurse(n-1) : 'ok') print "try recurse ", try print recurse(try) reread</lang>
Gnuplot 4.6 has a builtin STACK_DEPTH limit of 250, giving
try recurse 251 "/tmp/foo.gnuplot", line 2760: recursion depth limit exceeded
Gnuplot 4.4 and earlier has no limit except the C stack, giving a segv or whatever eventually.
Go
Go features stacks that grow as needed making the effective recursion limits relatively large.
Pre-Go 1.2 this could be all of memory and the program would grow without bounds until the system swap space was exhausted and the program was killed (either by the a run-time panic after an allocation failure or by the operating system killing the process).
Go 1.2 set a limit to the maximum amount of memory that can be used by a single goroutine stack.
The initial setting is 1 GB on 64-bit systems, 250 MB on 32-bit systems.
The default can be changed by SetMaxStack in the runtime/debug package. It is documented as "useful mainly for limiting the damage done by goroutines that enter an infinite recursion."
<lang go>package main
import ( "flag" "fmt" "runtime/debug" )
func main() { stack := flag.Int("stack", 0, "maximum per goroutine stack size or 0 for the default") flag.Parse() if *stack > 0 { debug.SetMaxStack(*stack) } r(1) }
func r(l int) { if l%1000 == 0 { fmt.Println(l) } r(l + 1) }</lang>
Run without arguments on a 64-bit system:
- Output:
[…] 4471000 4472000 4473000 runtime: goroutine stack exceeds 1000000000-byte limit fatal error: stack overflow runtime stack: runtime.throw(0x5413ae) /usr/local/go/src/pkg/runtime/panic.c:520 +0x69 runtime.newstack() /usr/local/go/src/pkg/runtime/stack.c:770 +0x486 runtime.morestack() /usr/local/go/src/pkg/runtime/asm_amd64.s:228 +0x61 goroutine 16 [stack growth]: main.r(0x444442) […]/rosetta/stack_size/stack.go:9 fp=0xc2680380c8 sp=0xc2680380c0 main.r(0x444441) […]/rosetta/stack_size/stack.go:13 +0xc5 fp=0xc268038140 sp=0xc2680380c8 main.r(0x444440) […] ...additional frames elided... created by _rt0_go /usr/local/go/src/pkg/runtime/asm_amd64.s:97 +0x120 goroutine 19 [finalizer wait]: runtime.park(0x412a20, 0x542ce8, 0x5420a9) /usr/local/go/src/pkg/runtime/proc.c:1369 +0x89 runtime.parkunlock(0x542ce8, 0x5420a9) /usr/local/go/src/pkg/runtime/proc.c:1385 +0x3b runfinq() /usr/local/go/src/pkg/runtime/mgc0.c:2644 +0xcf runtime.goexit() /usr/local/go/src/pkg/runtime/proc.c:1445 exit status 2
Run with "-stack 262144000" (to simulate the documented 250 MB limit on a 32-bit system):
- Output:
[…] 1117000 1118000 runtime: goroutine stack exceeds 262144000-byte limit fatal error: stack overflow […]
On a 32-bit system an int is 32 bits so the maximum value to debug.SetMaxStack is 2147483647 (nearly 2 GB).
On a 64-bit system an int is usually 64 bits so the maximum value will much larger, more than the available memory. Thus setting the maximum value will either exhaust all the system memory and swap (as with pre-Go 1.2) or will result in a allocation failure and run-time panic (e.g. 32-bit systems often have more memory and swap in total than the memory accessible to a single user program due to the limits of a 32 bit address space shared with the kernel).
Note, unlike with some other systems, increasing or changing this value only changes the allocation limit. The stack still starts out very small and only grows as needed, there is no large stack pre-allocation even when using a very high limit. Also note that this is per-goroutine, each goroutine can recurse independently and approach the limit.
The above code built pre-Go 1.2 (without the then non-existent debug.SetMaxStack call) and
run on a 1 GB RAM machine with 2.5 GB swap filled available RAM quickly, at a recursion depth of about 10M.
It took a several minutes to exhaust swap before exiting with this trace: (as you see, at a depth of over 25M.)
[…] 25611000 25612000 25613000 25614000 throw: out of memory (FixAlloc) runtime.throw+0x43 /home/sonia/go/src/pkg/runtime/runtime.c:102 runtime.throw(0x80e80c8, 0x1) runtime.FixAlloc_Alloc+0x76 /home/sonia/go/src/pkg/runtime/mfixalloc.c:43 runtime.FixAlloc_Alloc(0x80eb558, 0x2f) runtime.stackalloc+0xfb /home/sonia/go/src/pkg/runtime/malloc.c:326 runtime.stackalloc(0x1000, 0x8048c44) runtime.newstack+0x140 /home/sonia/go/src/pkg/runtime/proc.c:768 runtime.newstack() runtime.morestack+0x4f /home/sonia/go/src/pkg/runtime/386/asm.s:220 runtime.morestack() ----- morestack called from goroutine 1 ----- main.r+0x1a /home/sonia/t.go:9 main.r(0x186d801, 0x0) main.r+0x95 /home/sonia/t.go:13 main.r(0x186d800, 0x0) main.r+0x95 /home/sonia/t.go:13 main.r(0x186d7ff, 0x0) main.r+0x95 /home/sonia/t.go:13 main.r(0x186d7fe, 0x0) main.r+0x95 /home/sonia/t.go:13 main.r(0x186d7fd, 0x0) ... (more of the same stack trace omitted) ----- goroutine created by ----- _rt0_386+0xc1 /home/sonia/go/src/pkg/runtime/386/asm.s:80 goroutine 1 [2]: runtime.entersyscall+0x6f /home/sonia/go/src/pkg/runtime/proc.c:639 runtime.entersyscall() syscall.Syscall+0x53 /home/sonia/go/src/pkg/syscall/asm_linux_386.s:33 syscall.Syscall() syscall.Write+0x5c /home/sonia/go/src/pkg/syscall/zsyscall_linux_386.go:734 syscall.Write(0x1, 0x977e4f18, 0x9, 0x40, 0x9, ...) os.*File·write+0x39 /home/sonia/go/src/pkg/os/file_unix.go:115 os.*File·write(0x0, 0x0, 0x9, 0x40, 0x9, ...) os.*File·Write+0x98 /home/sonia/go/src/pkg/os/file.go:141 os.*File·Write(0xbffe1980, 0x8, 0x9, 0x8048cbf, 0x186d6b4, ...) ----- goroutine created by ----- _rt0_386+0xc1 /home/sonia/go/src/pkg/runtime/386/asm.s:80
Gri
In Gri 2.12.23 the total depth of command calls is limited to an internal array size cmd_being_done_LEN which is 100. There's no protection or error check against exceeding this, so the following code segfaults shortly after 100,
<lang Gri>`Recurse' {
show .depth.
.depth. = {rpn .depth. 1 +}
Recurse
} .depth. = 1 Recurse</lang>
Groovy
Solution: <lang groovy>def recurse; recurse = {
try {
recurse (it + 1)
} catch (StackOverflowError e) {
return it
}
}
recurse(0)</lang>
- Output:
387
Haskell
<lang haskell>import Debug.Trace (trace)
recurse :: Int -> Int recurse n = trace (show n) recurse (succ n)
main :: IO () main = print $ recurse 1</lang>
Or point-free: <lang haskell>import Debug.Trace (trace) import Data.Function (fix)
recurse :: Int -> Int recurse = fix ((<*> succ) . flip (trace . show))
main :: IO () main = print $ recurse 1</lang>
Or, more practically, testing up to a given depth:
<lang haskell>import Debug.Trace (trace)
testToDepth :: Int -> Int -> Int testToDepth max n
| n >= max = max | otherwise = trace (show n) testToDepth max (succ n)
main :: IO () main = print $ testToDepth 1000000 1</lang>
- Output:
... 999987 999988 999989 999990 999991 999992 999993 999994 999995 999996 999997 999998 999999 1000000
hexiscript
<lang hexiscript>fun rec n
println n rec (n + 1)
endfun
rec 1</lang>
HolyC
The point at which a stack overflow occurs varies depending upon how many parameters passed onto the stack. Running the code from within the editor on a fresh boot of TempleOS will cause a stack overflow when i is larger than ~8100.
<lang holyc>U0 Recurse(U64 i) {
Print("%d\n", i);
Recurse(i + 1);
}
Recurse(0);</lang>
i
<lang i>function test(counter) { print(counter) test(counter+1) }
software { test(0) }</lang>
Icon and Unicon
<lang Icon>procedure main() envar := "MSTKSIZE" write(&errout,"Program to test recursion depth - dependant on the environment variable ",envar," = ",\getenv(envar)|&null) deepdive() end
procedure deepdive() static d initial d := 0 write( d +:= 1) deepdive() end</lang> Note: The stack size environment variable defaults to about 50000 words. This terminates after approximately 3500 recursions (Windows). The interpreter should terminate with a 301 error, but currently this does not work.
Inform 7
<lang inform7>Home is a room.
When play begins: recurse 0.
To recurse (N - number): say "[N]."; recurse N + 1.</lang>
Using the interpreters built into Windows build 6F95, a stack overflow occurs after 6529 recursions on the Z-machine or 2030 recursions on Glulx.
J
Testing stack depth can be risky because the OS may shut down J in the limiting case. To portably test stack depth it's best to run jconsole and display a count as each stack frame is entered.
Note also that task assumes that all stack frames must be the same size, which is probably not the case.
<lang J>(recur=: verb def 'recur smoutput N=:N+1')N=:0</lang>
This above gives a stack depth of 9998 on one machine.
Note also, that ^: can be used for induction, and does not have stack size limits, though it does require that the function involved is a mathematical function of known variables -- and this is not always the case (for example, Markov processes typically use non-functions or "functions of unknown variables").
Java
<lang Java> public class RecursionTest {
private static void recurse(int i) {
try {
recurse(i+1); } catch (StackOverflowError e) { System.out.print("Recursion depth on this system is " + i + "."); }
}
public static void main(String[] args) {
recurse(0);
}
} </lang>
- Output:
Recursion depth on this system is 10473.
Settings:
Default size of stack is 320 kB.. To extend the memory allocated for stack can be used switch -Xss with the memmory limits. For example: java -cp . -Xss1m RecursionTest (set the stack size to 1 MB).
JavaScript
<lang javascript> function recurse(depth) {
try
{
return recurse(depth + 1);
}
catch(ex)
{
return depth;
}
}
var maxRecursion = recurse(1); document.write("Recursion depth on this system is " + maxRecursion);</lang>
- Output:
(Chrome)
Recursion depth on this system is 10473.
- Output:
(Firefox 1.6.13)
Recursion depth on this system is 3000.
- Output:
(IE6)
Recursion depth on this system is 2552.
jq
Recent versions of jq (after July 1, 2014, i.e. after version 1.4) include some "Tail Call Optimizations" (TCO). As a result, tail-recursive functions of arity 0 will run indefinitely in these later versions. The TCO optimizations also speed up other recursive functions.
Accordingly we present two test functions and show the results using jq 1.4 and using a version of jq with TCO optimizations.
Arity-0 Function <lang jq>def zero_arity:
if (. % 1000000 == 0) then . else empty end, ((.+1)| zero_arity);
1|zero_arity</lang> Arity-1 Function <lang jq>def with_arity(n):
if (n % 1000 == 0) then n else empty end, with_arity(n+1);
with_arity(1)</lang>
Results using jq 1.4 <lang sh>
- Arity 0 - without TCO:
... 23000000 # 1.62 GB 25000000
- error: can't allocate region
user 0m54.558s sys 0m2.773s
- Arity 1 - without TCO:
... 77000 # 23.4 MB ... 85000 # 23.7 MB 90000 # 25.4 MB 237000 # 47.4 MB (5h:08) 242000 # 50.0 MB (5h:14m)
- [job cancelled manually after over 5 hours]
</lang> Results using jq with TCO
The arity-0 test was stopped after the recursive function had been called 100,000,000 (10^8) times. The memory required did not grow beyond 360 KB (sic). <lang sh> $ time jq -n -f Find_limit_of_recursions.jq ... 10000000 # 360 KB ... 100000000 # 360 KB
- [job cancelled to get a timing]
user 2m0.534s sys 0m0.329s </lang>
The arity-1 test process was terminated simply because it had become too slow; at that point it had only consumed about 74.6K MB. <lang sh> ... 56000 # 9.9MB ... 95000 # 14.8 MB 98000 # 15.2 MB 99000 # 15.4 MB 100000 # 15.5 MB 127000 # 37.4 MB 142000 # 37.4 MB 254000 # 74.6 MB 287000 # 74.6 MB 406000 # 74.6 MB (8h:50m) 412000 # 74.6 MB (9h:05m)
- [job cancelled manually after over 9 hours]</lang>
Discussion
Even without the TCO optimizations, the effective limits for recursive jq functions are relatively high:
- the arity-0 function presented here proceeded normally beyond 25,000,000 (25 million) iterations;
- the arity-1 function is more effectively constrained by performance than by memory: the test process was manually terminated after 242,000 iterations.
With the TCO optimizations:
- the arity-0 function is not only unconstrained by memory but is fast and remains fast; it requires only 360 KB (that is KB).
- the arity-1 function is, once again, more effectively constrained by performance than by memory: the test process was terminated after 412,000 iterations simply because it had become too slow; at that point it had only consumed about 74.6 MB.
Julia
This solution includes two versions of the function for probing recursion depth. The Clean version is perhaps more idiomatic. However the Dirty version, by using a global variable for the depth counter and minimizing the complexity of the called code reaches a significantly greater depth of recursion.
Clean <lang Julia> function divedivedive(d::Int)
try
divedivedive(d+1)
catch
return d
end
end </lang> Dirty <lang Julia> function divedivedive()
global depth depth += 1 divedivedive()
end </lang> Main <lang Julia> depth = divedivedive(0) println("A clean dive reaches a depth of ", depth, ".")
depth = 0 try
divedivedive()
end println("A dirty dive reaches a depth of ", depth, ".") </lang>
- Output:
A clean dive reaches a depth of 21807. A dirty dive reaches a depth of 174454.
Kotlin
The result is a typical figure for Oracle's JVM 1.8.0_121 running on Ubuntu version 14.04, 64 bit using the default stack size.
One might have expected that the result would be the same (or only vary over a small range) for a given configuration but in fact the results are all over the place - running the program a number of times I obtained figures as high as 26400 and as low as 9099! I have no idea why. <lang scala>// version 1.1.2
fun recurse(i: Int) {
try {
recurse(i + 1)
}
catch(e: StackOverflowError) {
println("Limit of recursion is $i")
}
}
fun main(args: Array<String>) = recurse(0)</lang>
- Output:
10367
Liberty BASIC
Checks for the case of gosub & for proper subroutine. <lang lb> 'subroutine recursion limit- end up on 475000
call test 1
sub test n
if n mod 1000 = 0 then locate 1,1: print n call test n+1
end sub </lang>
<lang lb> 'gosub recursion limit- end up on 5767000 [test]
n = n+1 if n mod 1000 = 0 then locate 1,1: print n
gosub [test] </lang>
LIL
lil.c allows an optional build time value to set a limit on recursion: <lang c>/* Enable limiting recursive calls to lil_parse - this can be used to avoid call stack
* overflows and is also useful when running through an automated fuzzer like AFL */
/*#define LIL_ENABLE_RECLIMIT 10000*/</lang>
Otherwise, it is a race to run out of stack:
- Output:
Little Interpreted Language Interactive Shell
# func recur {n} {print $n; inc n; recur $n}
recur
# recur
1
2
...
37323
37324
Segmentation fault (core dumped)
That number will varying depending on system and state of system.
Logo
Like Scheme, Logo guarantees tail call elimination, so recursion is effectively unbounded. You can catch a user interrupt though to see how deep you could go.
<lang logo>make "depth 0
to recurse
make "depth :depth + 1 recurse
end
catch "ERROR [recurse]
; hit control-C after waiting a while
print error ; 16 Stopping... recurse [make "depth :depth + 1] (print [Depth reached:] :depth) ; some arbitrarily large number</lang>
LSL
I ran this twice and got 1891 and 1890; probably varies with the number Avatars on a Sim and other variables I can't control.
Originally I had it without the OwnerSay in the recursive function. Generally, if LSL has a Runtime Error it just shouts on the DEBUG_CHANNEL and skips to the next statement (which would have returned to the next statement in state_entry() said the highest number it had achieved) but, it just shouted "Script run-time error. Object: Stack-Heap Collision" on debug and quit running.
To test it yourself; rez a box on the ground, and add the following as a New Script. <lang LSL>integer iLimit_of_Recursion = 0; Find_Limit_of_Recursion(integer x) { llOwnerSay("x="+(string)x); iLimit_of_Recursion = x; Find_Limit_of_Recursion(x+1); } default { state_entry() { Find_Limit_of_Recursion(0); llOwnerSay("iLimit_of_Recursion="+(string)iLimit_of_Recursion); } } </lang>
- Output:
[2012/07/07 18:40] Object: x=0 [2012/07/07 18:40] Object: x=1 [2012/07/07 18:40] Object: x=2 ... ... ... ... ... [2012/07/07 18:41] Object: x=1888 [2012/07/07 18:41] Object: x=1889 [2012/07/07 18:41] Object: x=1890 [2012/07/07 18:41] Object: Object [script:New Script] Script run-time error [2012/07/07 18:41] Object: Stack-Heap Collision
Lua
Lua (version 5.3) support proper tail call, if the recursion is proper tail call there is no limit. Otherwise, it is limited by stack size set by the implementation. <lang Lua> local c = 0 function Tail(proper)
c = c + 1 if proper then if c < 9999999 then return Tail(proper) else return c end else return 1/c+Tail(proper) -- make the recursive call must keep previous stack end
end
local ok,check = pcall(Tail,true) print(c, ok, check) c=0 ok,check = pcall(Tail,false) print(c, ok, check) </lang>
- Output:
9999999 true 9999999 333325 false D:\00EXE\share\lua\5.3\test.lua:57: stack overflow
M2000 Interpreter
Modules & Functions
<lang M2000 Interpreter> Module checkit {
Global z
Function a {
z++
=a()
}
try {
m=a()
}
Print z
z<=0
Function a {
z++
call a()
}
try {
call a()
}
Print z
z<=0
Module m {
z++
Call m
}
try {
call m
}
Print z
z<=0
\\ without Call a module can't call itself
\\ but can call something global, and that global can call back
Module Global m1 {
z++
m2
}
Module Global m2 {
z++
m1
}
try {
call m1
}
Print z
} Checkit </lang> In Wine give these:
4030 8473 (plus 2 because we have Checkit inside a Z so these are two calls) 8473 (the same as above) 11225 (the same as above)
Subroutines
A lot of languages have a subroutine as a function without return value. As we see before, M2000 has Modules (as procedures) and Functions as that can be called as procedures too. These "procedures" can use only globals and anything they make for them. So what is a subroutine in Μ2000?
Subroutines are part of modules/functions. They haven't execution object, and they have to use parent object. So this parent object has the return stack, and use heap for this. So we can set a limit with Recursion.Limit to say 500000.
So a subroutine is code with module's scope, with recursion and local definitions. Utilizing current stack we can get results, or we can use by reference parameters to get results too.
We have to use statement Local for local variables and arrays who shadows same name variables or arrays. Parent can be the module/function as the caller, or another subroutine, or the same, but all have the same parent, the module/function.
<lang M2000 Interpreter>
Module Checkit {
\\ recursion for subs controled by a value
\\ change limit get a list of numbers from 1 to limit
Recursion.Limit 10
function FindZ {
z=1
Try {
CallmeAgain(1)
}
=Abs(z)
Sub CallmeAgain(x)
z--
CallmeAgain(x+1)
z++
End Sub
}
z=FindZ()
Print "Calls:"; z
NormalCall(1)
Sub NormalCall(x)
Print x
z--
if z>0 then NormalCall(x+1)
z++
End Sub
} Checkit </lang>
Mathematica / Wolfram Language
The variable $RecursionLimit can be read for its current value or set to different values. eg <lang>$RecursionLimit=10^6</lang> Would set the recursion limit to one million.
MATLAB / Octave
The recursion limit can be 'get' and 'set' using the "get" and "set" keywords.
Sample Usage: <lang MATLAB>>> get(0,'RecursionLimit')
ans =
500
>> set(0,'RecursionLimit',2500) >> get(0,'RecursionLimit')
ans =
2500</lang>
Maxima
<lang maxima>f(p) := f(n: p + 1)$ f(0); Maxima encountered a Lisp error:
Error in PROGN [or a callee]: Bind stack overflow.
Automatically continuing. To enable the Lisp debugger set *debugger-hook* to nil.
n; 406</lang>
МК-61/52
<lang>П2 ПП 05 ИП1 С/П ИП0 ИП2 - x<0 20 ИП0 1 + П0 ПП 05 ИП1 1 + П1 В/О</lang>
Modula-2
<lang modula2>MODULE recur;
IMPORT InOut;
PROCEDURE recursion (a : CARDINAL);
BEGIN
InOut.Write ('.'); (* just count the dots.... *)
recursion (a + 1)
END recursion;
BEGIN
recursion (0)
END recur.</lang> Producing this: <lang Modula-2> jan@Beryllium:~/modula/rosetta$ recur >testfile Segmentation fault jan@Beryllium:~/modula/rosetta$ ls -l -rwxr-xr-x 1 jan users 20032 2011-05-20 00:26 recur* -rw-r--r-- 1 jan users 194 2011-05-20 00:26 recur.mod -rw-r--r-- 1 jan users 523264 2011-05-20 00:26 testfile jan@Beryllium:~/modula/rosetta$ wc testfile
0 1 523264 testfile</lang>
So the recursion depth is just over half a million.
MUMPS
<lang MUMPS>RECURSE
IF $DATA(DEPTH)=1 SET DEPTH=1+DEPTH IF $DATA(DEPTH)=0 SET DEPTH=1 WRITE !,DEPTH_" levels down" DO RECURSE QUIT</lang>
End of the run ...
1918 levels down 1919 levels down 1920 levels down DO RECURSE ^ <FRAMESTACK>RECURSE+4^ROSETTA USER 72d0>
Nanoquery
<lang nanoquery>def recurse(counter)
println counter
counter += 1
recurse(counter)
end
recurse(1)</lang>
- Output:
1 2 3 ... 456 457 458 %recursion depth exception: recursion too deep while calling function 'recurse'
Neko
<lang ActionScript>/**
Recursion limit, in Neko
- /
/* This version is effectively unlimited, (50 billion test before ctrl-c) */ sum = 0.0 counter = 0 tco = function(n) {
sum += n counter += 1 if n > 10000000 return n else tco(n + 1)
}
try $print("Tail call recursion: ", tco(0), " sum: ", sum, "\n") catch with $print("tco counter: ", counter, " ", with, "\n")
/* Code after tail, these accumulate stack, will run out of space */ sum = 0.0 counter = 0 recurse = function(n) {
sum += n counter += 1 if n > 1000000 return n else recurse(n + 1) return sum
}
try $print("Recurse: ", recurse(0), " sum: ", sum, "\n") catch with $print("recurse limit exception: ", counter, " ", with, "\n")</lang>
- Output:
prompt$ nekoc recursion-limit.neko prompt$ neko recursion-limit.n Tail call recursion: 10000001 sum: 50000015000001 recurse limit exception: 52426 Stack Overflow
NetRexx
Like Java, NetRexx memory allocation is managed by the JVM under which it is run. The following sample presents runtime memory allocations then begins the recursion run. <lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols binary
import java.lang.management.
memoryInfo() digDeeper(0)
/**
* Just keep digging * @param level depth gauge */
method digDeeper(level = int) private static binary
do
digDeeper(level + 1)
catch ex = Error
System.out.println('Recursion got' level 'levels deep on this system.')
System.out.println('Recursion stopped by' ex.getClass.getName())
end
return
/**
* Display some memory usage from the JVM * @see ManagementFactory * @see MemoryMXBean * @see MemoryUsage */
method memoryInfo() private static
mxBean = ManagementFactory.getMemoryMXBean() -- get the MemoryMXBean hmMemoryUsage = mxBean.getHeapMemoryUsage() -- get the heap MemoryUsage object nmMemoryUsage = mxBean.getNonHeapMemoryUsage() -- get the non-heap MemoryUsage object say 'JVM Memory Information:' say ' Heap:' hmMemoryUsage.toString() say ' Non-Heap:' nmMemoryUsage.toString() say '-'.left(120, '-') say return
</lang>
- Output:
JVM Memory Information:
Heap: init = 0(0K) used = 2096040(2046K) committed = 85000192(83008K) max = 129957888(126912K)
Non-Heap: init = 24317952(23748K) used = 5375328(5249K) committed = 24317952(23748K) max = 136314880(133120K)
------------------------------------------------------------------------------------------------------------------------
Recursion got 9673 levels deep on this system.
Recursion stopped by java.lang.StackOverflowError
Nim
<lang nim>proc recurse(i): int =
echo i recurse(i+1)
echo recurse(0)</lang> Compiled without optimizations it would stop after 87317 recursions. With optimizations on recurse is translated into a tail-recursive function, without any recursion limit. Instead of waiting for the 87317 recursions you compile with debuginfo activated and check with gdb:
nim c --debuginfo --lineDir:on recursionlimit.nim
OCaml
When the recursion is a "tail-recursion" there is no limit. Which is important because being a functional programming language, OCaml uses recursion to make loops.
If the recursion is not a tail one, the execution is stopped with the message "Stack overflow": <lang ocaml># let last = ref 0 ;; val last : int ref = {contents = 0}
- let rec f i =
last := i; i + (f (i+1)) ;;
val f : int -> int = <fun>
- f 0 ;;
stack overflow during evaluation (looping recursion?).
- !last ;;
- : int = 262067</lang>
here we see that the function call stack size is 262067.
<lang ocaml>(* One can build a function from the idea above, catching the exception *)
let rec_limit () =
let last = ref 0 in let rec f i = last := i; 1 + f (i + 1) in try (f 0) with Stack_overflow -> !last
rec_limit ();; 262064
(* Since with have eaten some stack with this function, the result is slightly lower. But now it may be used inside any function to get the available stack space *)</lang>
Oforth
Limit found is 173510 on Windows system. Should be more on Linux system.
<lang Oforth>: limit 1+ dup . limit ;
0 limit</lang>
ooRexx
Using ooRexx for the program shown under Rexx:
rexx pgm 1>x1 2>x2
puts the numbers in x1 and the error messages in x2
...
2785
2786
8 *-* call self
....
8 *-* call self
3 *-* call self
Error 11 running C:\work.ooRexx\wc\main.4.1.1.release\Win32Rel\StreamClasses.orx line 366: Control stack full
Error 11.1: Insufficient control stack space; cannot continue execution
Oz
Oz supports an unbounded number of tail calls. So the following code can run forever with constant memory use (although the space used to represent Number will slowly increase):
<lang oz>declare
proc {Recurse Number}
{Show Number}
{Recurse Number+1}
end
in
{Recurse 1}</lang>
With non-tail recursive functions, the number of recursions is only limited by the available memory.
PARI/GP
As per "Recursive functions" in the Pari/GP users's manual. <lang parigp>dive(n) = dive(n+1) dive(0)</lang>
The limit is the underlying C language stack. Deep recursion is detected before the stack is completely exhausted (by checking RLIMIT_STACK) so a gp level error is thrown instead of a segfault.
Pascal
See Delphi
Perl
Maximum recursion depth is memory dependent.
<lang perl>my $x = 0; recurse($x);
sub recurse ($x) {
print ++$x,"\n"; recurse($x);
}</lang>
1 2 ... ... 10702178 10702179 Out of memory!
Phix
On a 32-bit version the limit is an impressive 34 million. Of course on real word apps with more parameters etc it will be smaller. Unfortunately other problems are stopping me from testing this on a 64-bit version right now. <lang Phix>atom t1 = time()+1
integer depth = 0
procedure recurse()
if time()>t1 then
?depth
t1 = time()+1
end if
depth += 1
-- only 1 of these will ever get called, of course...
recurse()
recurse()
recurse()
end procedure
recurse()</lang>
- Output:
C:\Program Files (x86)\Phix>p e01 8336837 16334140 20283032 21863323 22547975 22875708 23227196 23536921 24051004 24902668 25518908 26211370 26899260 27457596 27946743 28627343 29129830 29811260 31081002 31893231 32970812 33612604 34624828 34886703 Your program has run out of memory, one moment please C:\Program Files (x86)\Phix\e01.exw:48 in procedure recurse() memory allocation failure ... called from C:\Program Files (x86)\Phix\e01.exw:48 in procedure recurse() ... called from C:\Program Files (x86)\Phix\e01.exw:48 in procedure recurse() ... called from C:\Program Files (x86)\Phix\e01.exw:48 in procedure recurse() ... called from C:\Program Files (x86)\Phix\e01.exw:48 in procedure recurse() Global & Local Variables --> see C:\Program Files (x86)\Phix\ex.err Press Enter... C:\Program Files (x86)\Phix>
It takes about 25 seconds to build that stack and slightly longer to tear it down. You should also note that somewhat less clean error reports are likely: even the above could theoretically fail mid-sprintf and hence exercise a completely different error handling path, and there are likely to be several hundred different ways to fail when there is no more memory.
PHP
<lang PHP><?php function a() {
static $i = 0; print ++$i . "\n"; a();
} a();</lang>
- Output:
1 2 3 [...] 597354 597355 597356 597357 597358 Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 261904 bytes) in [script-location.php] on line 5
PicoLisp
The 64-bit and the 32-bit version behave slightly different. While the 32-bit version imposes no limit on its own, and relies on the 'ulimit' setting of the caller, the 64-bit version segments the available stack (likewise depending on 'ulimit') and allows each (co)routine a maximal stack size as configured by 'stack'.
32-bit version
$ ulimit -s 8192 $ pil + : (let N 0 (recur (N) (recurse (msg (inc N))))) ... 730395 730396 730397 Segmentation fault
64-bit version
$ ulimit -s unlimited $ pil + : (stack) # The default stack segment size is 64 MB -> 64 : (co 'a (yield 7)) # Start a dummy coroutine -> 7 : (let N 0 (recur (N) (recurse (println (inc N))))) ... 2475 2476 2477 Stack overflow ?
PL/I
<lang PL/I> recurs: proc options (main) reorder; dcl sysprint file; dcl mod builtin;
dcl ri fixed bin(31) init (0);
recursive: proc recursive;
ri += 1; if mod(ri, 1024) = 1 then put data(ri);
call recursive();
end recursive;
call recursive(); end recurs; </lang>
Result (abbreviated):
... RI= 4894721; RI= 4895745; RI= 4896769; RI= 4897793; RI= 4898817;
At this stage the program, running on z/OS with a REGION=0M on the EXEC statement (i.e. grab as much storage as you like), ABENDs with a USER COMPLETION CODE=4088 REASON CODE=000003EC
Obviously, if the procedure recursive would have contained local variables, the depth of recursion would be reached much earlier...
PowerShell
When the overflow exception is thrown, the entire stack collapses. But anticipating this, we can leverage PowerShell features to get and process all of the results from before the exception. In PowerShell, when anything is written the the output stream WITHOUT the "Return" keyword, processing continues, so we can successfully return data from the function even if the function never successfully completes. The original calling line will also be terminated when the exception is thrown, but if instead of assigning it to a variable, we send the results to a pipeline, we can process the earlier results before handling the exception. <lang PowerShell> function TestDepth ( $N )
{
$N
TestDepth ( $N + 1 )
}
try
{
TestDepth 1 | ForEach { $Depth = $_ }
}
catch
{
"Exception message: " + $_.Exception.Message
}
"Last level before error: " + $Depth </lang>
- Output:
Exception message: The script failed due to call depth overflow. Last level before error: 4994
PureBasic
The recursion limit is primarily determined by the stack size. The stack size can be changed when compiling a program by specifying the new size using '/stack:NewSize' in the linker file.
Procedural
In addition to the stack size the recursion limit for procedures is further limited by the procedure's parameters and local variables which are also stored on the same stack. <lang PureBasic>Procedure Recur(n)
PrintN(str(n)) Recur(n+1)
EndProcedure
Recur(1)</lang>
Stack overflow after 86317 recursions on x86 Vista.
Classic
<lang PureBasic>rec:
PrintN(str(n)) n+1 Gosub rec Return</lang> Stack overflow after 258931 recursions on x86 Vista.
Python
<lang python>import sys print(sys.getrecursionlimit())</lang>
To set it:
<lang python>import sys sys.setrecursionlimit(12345)</lang>
Or, we can test it:
<lang python>def recurse(counter):
print(counter) counter += 1 recurse(counter)</lang>
Giving:
<lang python>File "<stdin>", line 2, in recurse RecursionError: maximum recursion depth exceeded while calling a Python object 996</lang>
Which we could change if we wanted to.
We can catch the RecursionError and keep going a bit further:
<lang python>def recurseDeeper(counter):
try:
print(counter)
recurseDeeper(counter + 1)
except RecursionError:
print("RecursionError at depth", counter)
recurseDeeper(counter + 1)</lang>
Giving:
<lang python>1045 Fatal Python error: Cannot recover from stack overflow.</lang>
R
R's recursion is counted by the number of expressions to be evaluated, rather than the number of function calls. <lang r>#Get the limit options("expressions")
- Set it
options(expressions = 10000)
- Test it
recurse <- function(x) {
print(x) recurse(x+1)
} recurse(0)</lang>
Racket
<lang Racket>#lang racket (define (recursion-limit)
(with-handlers ((exn? (lambda (x) 0))) (add1 (recursion-limit))))</lang>
This should theoretically return the recursion limit, as the function can't be tail-optimized and there's an exception handler to return a number when an error is encountered. For this to work one has to give the Racket VM the maximum possible memory limit and wait.
Raku
(formerly Perl 6) Maximum recursion depth is memory dependent. Values in excess of 1 million are easily achieved.
<lang perl6>my $x = 0; recurse;
sub recurse () {
++$x; say $x if $x %% 1_000_000; recurse;
}</lang>
- Output:
When manually terminated memory use was on the order of 4Gb:
1000000 2000000 3000000 4000000 5000000 6000000 7000000 8000000 9000000 10000000 ^C
Retro
When run, this will display the address stack depth until it reaches the max depth. Once the address stack is full, Retro will crash.
<lang Retro>: try -6 5 out wait 5 in putn cr try ;</lang>
REXX
recursive procedure
On (IBM's) VM/CMS, the limit of recursion was built-into CMS to stop run-away EXEC programs (this
included EXEC[0], EXEC2, and REXX) being called recursively; it was either 200 or 250 as I recall.
This limit was maybe changed later to allow the user to specify the limit. My memory is really fuzzy
about these details, it was over thirty years ago.
<lang rexx>/*REXX program finds the recursion limit: a subroutine that repeatably calls itself. */
parse version x; say x; say /*display which REXX is being used. */
- =0 /*initialize the numbers of invokes to 0*/
call self /*invoke the SELF subroutine. */
/* [↓] this will never be executed. */
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ self: procedure expose # /*declaring that SELF is a subroutine.*/
#=#+1 /*bump number of times SELF is invoked. */
say # /*display the number of invocations. */
call self /*invoke ourselves recursively. */</lang>
- output when using Regina 3.6 under Windows/XP Pro:
REXX-Regina_3.6(MT) 5.00 31 Dec 2011 . . . 164405 164406 164407 System resources exhausted
[Your mileage will vary.]
For BREXX 2.1.0, it was 251 For Regina 3.2, " " 3,641 For Regina 3.3, " " 4,234 For Regina 3.4, " " 945,144 For Regina 3.4P1, " " " For Regina 3.5, " " 164,560 For Regina 3.6, " " 164,407 For Regina 3.7, " " " For Regina 3.7RC1, " " " For Regina 3.8, " " " For Regina 3.8RC1, " " " For Regina 3.8.2, " " " For Regina 3.9.0, " " 164,527 For Regina 3.9.1, " " " For Regina 3.9.3, " " 164,398
Note that the above recursion limit will be less and it's dependent upon how much virtual memory the program itself uses,
this would include REXX variables and their values, and the program source (as it's kept in virtual memory also),
and the size of the REXX.EXE and REXX.DLL programs, and any other programs executing in the Windows DOS (including
either the CMD.EXE or COMMAND.COM) shell).
- output when using Personal REXX under Windows/XP Pro:
The recursion level wasn't captured, but the last number shown was 240.
REXX/Personal 4.00 21 Mar 1992
.
.
.
10 +++ call self
10 +++ call self
10 +++ call self
4 +++ call SELF
Error 5 on line 10 of D:\SELF.REX: Machine resources exhausted
- output when using R4 REXX under Windows/XP Pro:
REXX-r4 4.00 29 Apr 2012 . . . 505 506 507 An unexpected error occurred
- output when using ROO REXX under Windows/XP Pro:
REXX-roo 4.00 28 Jan 2007 . . . 380 381 382 An unexpected error occurred
recursive subroutine
All REXXes were executed under Windows/XP Pro. <lang rexx>/*REXX program finds the recursion limit: a subroutine that repeatably calls itself. */ parse version x; say x; say /*display which REXX is being used. */
- =0 /*initialize the numbers of invokes to 0*/
call self /*invoke the SELF subroutine. */
/* [↓] this will never be executed. */
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ self: #=#+1 /*bump number of times SELF is invoked. */
say # /*display the number of invocations. */
call self /*invoke ourselves recursively. */</lang>
- output (paraphrased and edited)
For BREXX 2.1.0, it was 251 For Regina 3.2, " " 4,234 For Regina 3.3, " " 3,641 For Regina 3.4, " " 945,144 For Regina 3.4P1, " " " For Regina 3.5, " " " For Regina 3.6, " " 828,441 For Regina 3.7, " " " For Regina 3.7RC1, " " " For Regina 3.8, " " " For Regina 3.8RC1, " " " For Regina 3.8.2, " " " For Regina 3.9.0, " " 828,441 For Regina 3.9.1, " " " For Regina 3.9.3, " " " For Personal REXX, it was 240 (the same) For R4, it was 507 (the same) For ROO, it was 382 (the same)
Ring
<lang ring> recurse(0)
func recurse x
see ""+ x + nl
recurse(x+1)
</lang>
Ruby
<lang ruby>def recurse x
puts x recurse(x+1)
end
recurse(0)</lang>
- Output:
Produces a SystemStackError
. . . 6074 recurse.rb:3:in `recurse': stack level too deep (SystemStackError) from recurse.rb:3:in `recurse' from recurse.rb:6
when tracking Stack overflow exceptions ; returns 8732 on my computer :
<lang ruby>def recurse n
recurse(n+1)
rescue SystemStackError
n
end
puts recurse(0)</lang>
Run BASIC
<lang runbasic>a = recurTest(1)
function recurTest(n) if n mod 100000 then cls:print n if n > 327000 then [ext]
n = recurTest(n+1)
[ext] end function</lang>
327000
Rust
<lang rust>fn recurse(n: i32) {
println!("depth: {}", n);
recurse(n + 1)
}
fn main() {
recurse(0);
}</lang>
- Output:
... depth: 18433 depth: 18434 depth: 18435 thread '<main>' has overflowed its stack An unknown error occurred To learn more, run the command again with --verbose.
Sather
<lang sather>class MAIN is
attr r:INT; recurse is r := r + 1; #OUT + r + "\n"; recurse; end; main is r := 0; recurse; end;
end;</lang>
Segmentation fault is reached when r is 130560.
Scala
<lang scala>def recurseTest(i:Int):Unit={
try{
recurseTest(i+1)
} catch { case e:java.lang.StackOverflowError =>
println("Recursion depth on this system is " + i + ".")
}
} recurseTest(0)</lang>
- Output:
depending on the current stack size
Recursion depth on this system is 4869.
If your function is tail-recursive the compiler transforms it into a loop. <lang scala>def recurseTailRec(i:Int):Unit={
if(i%100000==0) println("Recursion depth is " + i + ".")
recurseTailRec(i+1)
}</lang>
Scheme
<lang scheme>(define (recurse number)
(begin (display number) (newline) (recurse (+ number 1))))
(recurse 1)</lang> Implementations of Scheme are required to support an unbounded number of tail calls. Furthermore, implementations are encouraged, but not required, to support exact integers of practically unlimited size.
SenseTalk
<lang sensetalk>put recurse(1)
function recurse n
put n get the recurse of (n+1)
end recurse</lang> Recursion limit error is reached at 40.
Sidef
Maximum recursion depth is memory dependent. <lang ruby>func recurse(n) {
say n; recurse(n+1);
}
recurse(0);</lang>
- Output:
0 1 2 ... ... 357077 357078 357079
Smalltalk
In the Squeak dialect of Smalltalk:
<lang smalltalk> Object subclass: #RecursionTest instanceVariableNames: classVariableNames: poolDictionaries: category: 'RosettaCode' </lang>
Add the following method:
<lang smalltalk> counter: aNumber ^self counter: aNumber + 1 </lang>
Call from the Workspace:
<lang smalltalk> r := RecursionTest new. r counter: 1. </lang>
After some time the following error pops up:
Warning! Squeak is almost out of memory! Low space detection is now disabled. It will be restored when you close or proceed from this error notifier. Don't panic, but do proceed with caution. Here are some suggestions: If you suspect an infinite recursion (the same methods calling each other again and again), then close this debugger, and fix the problem. If you want this computation to finish, then make more space available (read on) and choose "proceed" in this debugger. Here are some ways to make more space available... * Close any windows that are not needed. * Get rid of some large objects (e.g., images). * Leave this window on the screen, choose "save as..." from the screen menu, quit, restart the Squeak VM with a larger memory allocation, then restart the image you just saved, and choose "proceed" in this window. If you want to investigate further, choose "debug" in this window. Do not use the debugger "fullStack" command unless you are certain that the stack is not very deep. (Trying to show the full stack will definitely use up all remaining memory if the low-space problem is caused by an infinite recursion!).
Other dialects raise an exception: <lang smalltalk> counter := 0. down := [ counter := counter + 1. down value ]. down on: RecursionError do:[
'depth is ' print. counter printNL
].</lang>
Swift
<lang swift>var n = 1
func recurse() {
print(n) n += 1 recurse()
}
recurse()</lang>
Tcl
<lang tcl>proc recur i {
puts "This is depth [incr i]"
catch {recur $i}; # Trap error from going too deep
} recur 0</lang> The tail of the execution trace looks like this:
This is depth 995 This is depth 996 This is depth 997 This is depth 998 This is depth 999
Note that the maximum recursion depth is a tunable parameter, as is shown in this program: <lang tcl># Increase the maximum depth interp recursionlimit {} 1000000 proc recur i {
if {[catch {recur [incr i]}]} {
# If we failed to recurse, print how far we got
puts "Got to depth $i"
}
} recur 0</lang> For Tcl 8.5 on this platform, this prints:
Got to depth 6610
At which point it has exhausted the C stack, a trapped error. Tcl 8.6 uses a stackless execution engine, and can go very deep if required:
Got to depth 999999
TSE SAL
<lang TSE SAL> // library: program: run: recursion: limit <description>will stop at 3616</description> <version>1.0.0.0.3</version> <version control></version control> (filenamemacro=runprrli.s) [kn, ri, su, 25-12-2011 23:12:02] PROC PROCProgramRunRecursionLimit( INTEGER I )
Message( I ) PROCProgramRunRecursionLimit( I + 1 )
END
PROC Main()
PROCProgramRunRecursionLimit( 1 )
END </lang>
TXR
<lang txrlisp>(set-sig-handler sig-segv
(lambda (signal async-p) (throw 'out)))
(defvar *count* 0)
(defun recurse ()
(inc *count*) (recurse))
(catch (recurse)
(out () (put-line `caught segfault!\nreached depth: @{*count*}`)))</lang>
- Output:
$ txr limit-of-recursion.tl caught segfault! reached depth: 10909
UNIX Shell
<lang bash>recurse() {
# since the example runs slowly, the following # if-elif avoid unuseful output; the elif was # added after a first run ended with a segmentation # fault after printing "10000" if $(($1 % 5000)) -eq 0 ; then echo $1; elif $1 -gt 10000 ; then echo $1 fi recurse $(($1 + 1))
}
recurse 0</lang>
The Bash reference manual says No limit is placed on the number of recursive calls, nonetheless a segmentation fault occurs at 13777 (Bash v3.2.19 on 32bit GNU/Linux)
Ursa
<lang ursa>def recurse (int counter)
try
recurse (+ counter 1)
catch recursionerror
out "the limit of recursion was " counter endl console
end try
end
recurse 1</lang>
VBA
<lang vb> Option Explicit
Sub Main()
Debug.Print "The limit is : " & Limite_Recursivite(0)
End Sub
Function Limite_Recursivite(Cpt As Long) As Long
Cpt = Cpt + 1 'Count On Error Resume Next Limite_Recursivite Cpt 'recurse On Error GoTo 0 Limite_Recursivite = Cpt 'return
End Function </lang>
- Output:
The limit is : 6442
VBScript
Haven't figured out how to see the depth. And this depth is that of calling the O/S rather than calling within.
<lang vb>'mung.vbs option explicit
dim c if wscript.arguments.count = 1 then c = wscript.arguments(0) c = c + 1 else c = 0 end if wscript.echo "[Depth",c & "] Mung until no good." CreateObject("WScript.Shell").Run "cscript Mung.vbs " & c, 1, true wscript.echo "[Depth",c & "] no good."</lang>
Okay, the internal limits version.
<lang vb>'mung.vbs option explicit
sub mung(c) dim n n=c+1 wscript.echo "[Level",n & "] Mung until no good" on error resume next mung n on error goto 0 wscript.echo "[Level",n & "] no good" end sub
mung 0</lang>
- Output:
(abbrev.)
[Level 1719] Mung until no good [Level 1720] Mung until no good [Level 1721] Mung until no good [Level 1722] Mung until no good [Level 1722] no good [Level 1721] no good [Level 1720] no good [Level 1719] no good
x86 Assembly
<lang asm> global main
section .text
main xor eax, eax call recurse ret
recurse add eax, 1 call recurse ret</lang>
I've used gdb and the command print $eax to know when the segmentation fault occurred. The result was 2094783.
Wren
I cannot find any published information on the maximum amount of memory that can be used by a fiber's stack - and hence the limit of recursion for a given function - but it appears to be 4 GB on a sufficiently large 64-bit system such as my own (32 GB) with no shell limit.
The final figure produced by the following script was 536,870,500 and multiplying by 8 (the number of bytes of storage required for the parameter 'n') gives 4,294,964,000 which is just 3,296 bytes short of 4 GB.
In Wren a fiber's stack starts small and is increased as required. It appears that the runtime makes no attempt to check for any limitation internally leaving the script to eventually segfault. <lang ecmascript>var f f = Fn.new { |n|
if (n%500 == 0) System.print(n) // print progress after every 500 calls
System.write("") // required to fix a VM recursion bug
f.call(n + 1)
} f.call(1)</lang>
- Output:
... 536870000 536870500 Segmentation fault (core dumped)
zkl
<lang zkl>fcn{self.fcn()}()</lang>
- Output:
Stack trace for VM#1 (): Cmd.__fcn#1_2 addr:3 args(0) reg(0) R <repeats 2096 times> Cmd.__constructor addr:3 args(0) reg(0) R startup.__constructor addr:2242 args(0) reg(1) ER startup.__constructor addr:2178 args(0) reg(22) Exception thrown: AssertionError(That is one big stack, infinite recursion?)
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