Out of index C/C++ -



Out of index C/C++ -

a typical declaration array in c/c++ is:

type name [elements];

where type valid type (such int, float...), name valid identifier , elements field (which enclosed in square brackets []), specifies length of array in terms of number of elements.

so declare array of int have 2 elements

int a[2]; a[3] =4;

why not throw exception?

out of bounds checking used higher level language java. in c/c++ not done default. gives little performance nail check bounds of array , hence c rationale have manually in case need offer best possible performance. c++ stl containers vector back upwards at() operation perform bound-checking , since can overload []-operator can enable bound-checks array-style access.

if array raw pointer statement array[i] comes downwards in c/c++:

*(array + i)

which simple add-on of address + offset. next statements equivalent:

*(array + i), *(i + array), array[i], i[array]

what happens internally take address stored in pointer, add together i-times size of array type , de-reference address.

so happens if specify index bigger array, access memory not belong array. read random info next array in memory. typical source of buffer-overflows if address written to. if memory trying access not belong process, segfault.

c++ c arrays indexing

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