stack frame & dangling pointer weirdness

[Alain De Vos]

On Thursday, 21 April 2022 at 06:57:41 UTC, drug wrote:
> On 21.04.2022 08:49, Alain De Vos wrote:
>> Following program:
>> ```
>> import std.stdio;
>> 
>> void main() @trusted
>> {
>> 
>> int *p=null;
>> void myfun(){
>>      int x=2;
>>      p=&x;
>>      writeln(p);
>>      writeln(x);
>> }
>> myfun();
>> *p=16;
>> writeln(p);
>> writeln(*p);
>> }
>> ```
>> 
>> outputs :
>> 7FFFFFFFDFAC
>> 2
>> 7FFFFFFFDFAC
>> 32767
>> 
>> I don't understand why. Would it be possible to explain  ?
>
> Like others have said `writeln` overwrites the memory. You can 
> check it by commenting `writeln(p);` out - then you get:
> ```d
> 7FFF23725D1C
> 2
> 16
> ```

No error was thrown during execution.
Should an error be thrown or is this optional by the operating 
system ?
How can i force an error to be thrown when doing something "bad" ?