How to define Array size dynamically

**softte** · 28-01-2009

Hi guys!

I'm taking over the C language after more than a year, and I suddenly collapsed a certainty

As far as I know, when you define an array of its size should be known at compile time, and in particular it should be a constant. Now, doing some evidence, I realize that compiling and running a program like this:

Code:

  # include <stdio.h> 

  int main (void) 
  ( 
     int c; 
     int DIM; 
     printf ( "Enter array size:"); 
     scanf ( "% d", & DIM); 
     int string [SIZE]; 
     for (c = 0; c <DIM, c + +) 
       string [c] = c; 
     printf ( "\ nFine \ n"); 
     return 0; 
  )

not only do not get errors in compiling, but not even a segmentation fault at runtime.

If you could explain to me why?

Accurate use gcc version 4.2.4 on Linux 2.6.24 64-bit

**Adley** · 28-01-2009

the C99 can be done, is the c + + which does not support

**softte** · 28-01-2009

I tried to fill this with g + +, and not even get a runtime error ...

Code:

 # include <iostream> 

  using namespace std; 

  int main (void) 
  ( 
     int d; 
   
     court << "Enter array size:"; 
     cin>> d; 
   
     int carrier [d]; 
   
     for (int i = 0; i <d-1, i + +) 
       vector [i] = i; 
   
     court << "Done!" <<endl; 
   
     return 0; 
  )

EDIT: Only if you fill a passing the-pedantic I get the warning on variable size of the array, but not a mistake ...

Code:

warning: ISO C90 forbids variable-size array 'string'

**Shell** · 28-01-2009

I tried to fill this with g + +, and not even get a runtime error ...

Code:

# include <iostream> 

  using namespace std; 

  int main (void) 
  ( 
     int d; 
   
     court << "Enter array size:"; 
     cin>> d; 
   
     int carrier [d]; 
   
     for (int i = 0; i <d-1, i + +) 
       vector [i] = i; 
   
     court << "Done!" <<endl; 
   
     return 0; 
  )

EDIT: Only if you fill a passing the-pedantic I get the warning on variable size of the array, but not a mistake ...

precisely because it prohibits not the C90 and C99 as the gcc compiler C99 is a string that is accepted, and its validity "imported" in c + +