No security leak - the information is stored in the same memory as
non-global variables. Its just that it is a bother to keep track of
global variables, avoid name-space collision, make sure they have correct
values etc.
When you encapsulate the data as private in classes, you know that only a
couple of methods of that class may change the data, thereby improving the
chance of the variables having the correct value.
An example: a linked list and a variable storing number of elements in the
list. Whenever an element is added or removed from the list, the count
variable must also be updated. If the list was global, some other code
might insert a new element but forget to update the counter.
An other example: How soon do your global variable get the correct value,
in case you can't assign the value in the declaration? You have to wait
until a specific function is called, but during this time, other code
might try to use the global variable. If it is encapsulated, the access
methods would know if it has been initialized or not.
Third example: in multithreaded environments, every access to the global
variable must be protected by a critical section or a mutex or similar, or
fatal things can happen to the application.
/Per W
On 30 Apr 2003, Christian Schaefer wrote:
> hi there!
>
> I wonder if there is any security issue in using global variables?
> are they just considered 'un-styleful' or are they a security leak?
>
> regards
> /christian
>
>
>
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