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Allocation problem [message #909727] Fri, 07 September 2012 16:47 Go to next message
Jordi Jacobs is currently offline Jordi Jacobs
Messages: 5
Registered: September 2012
Junior Member
Hi,

I can't get this to work:
/*
 ============================================================================
 Name        : hello.c
 Author      :
 Version     :
 Copyright   :
 Description : hello in C, Ansi-style
 ============================================================================
 */

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	int var1[1000000];
	printf("%i",var1[0]);
	return EXIT_SUCCESS;
}


I see this:
http://www.eclipse.org/forums/index.php/t/255620/

"-Wl,--stack,2097152" does not seem to work...

How can I fix this?

(I do want that array on a bigger stack.)

[Updated on: Fri, 07 September 2012 22:22]

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Re: Allocation problem [message #910021 is a reply to message #909727] Sat, 08 September 2012 11:50 Go to previous messageGo to next message
Jordi Jacobs is currently offline Jordi Jacobs
Messages: 5
Registered: September 2012
Junior Member
Now i've done this in linux eclips-cdt:

code:
#include <stdlib.h>
#include <stdio.h>
#include <sys/resource.h>

int main(void)
{
    const rlim_t kStackSize = 1024L * 1024L * 1024L;
    struct rlimit rl;
    int result;
    result = getrlimit(RLIMIT_STACK, &rl);
    printf("%i (%i)\n",(int)rl.rlim_cur,result);

    rl.rlim_cur = kStackSize;
    result = setrlimit(RLIMIT_STACK, &rl);
    printf("%i (%i)\n",(int)rl.rlim_cur,result);

    result = getrlimit(RLIMIT_STACK, &rl);
    printf("%i (%i)\n",(int)rl.rlim_cur,result);

    int k[2090000];
    printf("k\n");
    return EXIT_SUCCESS;
}



output:
8388608 (0)
1073741824 (0)
1073741824 (0)
k


code2:
int k[2090000]; ==> int k[2099000];


no output


Setting the RLIMIT_STACK to a bigger value does not seem to help...

Just to be sure: Each program has its own stack right? Because this linux command is throwing me off...

[Updated on: Sat, 08 September 2012 11:59]

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Re: Allocation problem [message #910031 is a reply to message #910021] Sat, 08 September 2012 12:29 Go to previous messageGo to next message
Jordi Jacobs is currently offline Jordi Jacobs
Messages: 5
Registered: September 2012
Junior Member
If I run the executable in a terminal I get this:
Segmentation fault (core dumped)

I like eclipse so far, but I don't like that it didn't show that error...

(Didn't find how to edit previous post...)

edit:
Lol that button was not there some seconds ago.

edit2:
valgrind gave this:
==7063== Process terminating with default action of signal 11 (SIGSEGV)
==7063==  Access not within mapped region at address 0x7FE7FE3A8
==7063==    at 0x400649: main (big_array.c:17)
==7063==  If you believe this happened as a result of a stack
==7063==  overflow in your program's main thread (unlikely but
==7063==  possible), you can try to increase the size of the
==7063==  main thread stack using the --main-stacksize= flag.
==7063==  The main thread stack size used in this run was 8388608.

[Updated on: Sat, 08 September 2012 12:45]

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Re: Allocation problem [message #910035 is a reply to message #910021] Sat, 08 September 2012 12:36 Go to previous messageGo to next message
Sunil Matta is currently offline Sunil Matta
Messages: 8
Registered: April 2012
Junior Member
Yes, each program has its own stack.
However, there are limits that you are restricted to. Check your env limits with ulimit for your stack limits. You are attempting to go way past allocated limits.

You are not getting any output because of your printf statement has no format specifier. change to printf("%d\n", k[0]);
Now you will probably get ouput AND a coredump due to going past the env limits.

Re: Allocation problem [message #910040 is a reply to message #910035] Sat, 08 September 2012 12:58 Go to previous messageGo to next message
Jordi Jacobs is currently offline Jordi Jacobs
Messages: 5
Registered: September 2012
Junior Member
Thanks for pointing me to env limits.

Ow no lol that was not my intent, the k is random (bad case of random). That was just to show if the programm reaches that point or not, output on screen just shows a "k".

edit:
Could you be specific about the ulimts because I can't seem to get it to work...
btw
The first output seems to indicate that the limit-change has succeeded...

edit3:
when I take:
const rlim_t kStackSize = 16L * 1024L * 1024L;
instead of:
const rlim_t kStackSize = 1024L * 1024L * 1024L;
the problem persists...
Is there any other parameter that i need to change?
Maybe this is some virtual limit while the program is running into the real limit (stack-allocation)?

edit4:
valgrind gives a warning:
"Warning: client switching stacks?  SP change: 0x7ff0000d0 --> 0x7fe7fe3d0
==8837==          to suppress, use: --max-stackframe=8396032 or greater"

(edit5: this warning is just because of the large change in the stack pointer as expected and the guess "switching stacks" is wrong)
also:
the error occurs on the line after the allocation
"Access not within mapped region at address 0x7FE7FE3C8
==8837==    at 0x40050C: main (big_array.c:32)"

line 32 being the next action

[Updated on: Sat, 08 September 2012 13:58]

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Re: Allocation problem [message #910060 is a reply to message #910040] Sat, 08 September 2012 14:17 Go to previous message
Jordi Jacobs is currently offline Jordi Jacobs
Messages: 5
Registered: September 2012
Junior Member
"The real limit" is set by the OS and ulimit is indeed the solution.

ulimit -s

==>
8192

ulimit -s 16384
ulimit -s

==>
16384

Thank you Sunil Matta.
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