declaring an array of 1000000 size

I was seeing a solution of a problem

in the solution an array is declared as

int vec[1000000]

when i copied the code and tried to run it on my system it gives me error
but when i submitted the same code on codechef i got correct answer.

while searching for the cause i found out that i cant declare array of that size because stack memory is limited.
i should declare it in heap using dynamic memory allocation
but my question is that how i got correct answer on codechef ?


It might be possible that your compiler flags are somewhat “ill-defined”, in the sense that you don’t allow so much stack memory to be used which basically means your stack-size has a different size limit than the one used by Codechef judge, but, I compiled that code in my system and it gave no errors or warnings…

I am using this to compile it:

gcc -Wall -ansi -pedantic -o teste teste.c -lm

This is my gcc version status:

gcc (Ubuntu/Linaro 4.7.3-1ubuntu1) 4.7.3
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO

You should re-check your compiler settings, as if the code works fine on my system and on Codechef, then the problem must be on your side…

Hope this helps!!

Best regards,


1 Like

when i checked my gcc version
it showed

gcc 3.4.2

copyright © 2004

i think its too old and that’s why its stack memory will be less than its current version.
thanks alot

I’m glad I could help you :slight_smile:

I’m not saying this will totally work and solve your problem but, if you declare your array globally then, i think even on old gcc compiler this will work.


yes its working.
but y?

Global variables are allocated in the heap memory, which is the memory where dynamically allocated memory resides.
Non-global variables are allocated in the stack which is typically much, much shorter… This a good trick to have present as it might help you even with newer compiler versions… :slight_smile:


I was having same problem while compiling some problem of codechef, but when i submitted it, got ac…

@abcdexter24 read my answer first

same as @kuruma

thanks it helped me in clearing some basic concepts…:slight_smile: