pointers - Array address in c++ -

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i have code :

int n; cin >> n; int array[n];  (int = 0; < n; ++i) {     cin >> array[i];   }  int tmp[n - 1]; tmp[0] = 1;

with input : 1 10 found value of array[0] changed , instead of 10 has same tmp[0].

then realized input length of tmp[] became zero. print address of array[] , tmp[] with:

printf("%d\n %d\n", array, tmp);

and found had same address.

i want figure out happen if array has length of 0; tried this:

int array[1]; array[0] = 10;  int tmp[0]; tmp[0] = 1;

address:

array[]: 1363909056 tmp[]  : 1363909052

it looks previous code (except input part). tmp[0] , array[0] has different values , address now.

and i'm confused tmp has smaller address array.

so question is:

  1. what happen if declare array of length zero?
  2. why these 2 codes works different? (they same me :) )

this called "undefined behavior". after declaring, in case

int tmp[0];

the next thing happens is:

tmp[0]=1;

since tmp[0] not exist, undefined behavior. problem not array declared size 0 (that's not kosher on own merits, not issue here), undefined behavior result of overwriting memory past end of array.


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