On 11/06/2021 10:44, Xi Ruoyao wrote:
> On Fri, 2021-06-11 at 10:37 +0100, Jonny Grant wrote:
>> Hello
>> This isn't real code, it's just an example to ask this question:
>>
>> Would GCC optimizer ever re-order these statements and cause a NULL ptr
>> de-reference SIGSEGV? I recall reading a Chris Lattner paper indicating
>> it could happen.
>>
>> void f(int * p)
>> {
>> if(!p)
>> {
>> return;
>> }
>>
>> printf("%d\n", *p);
>> }
>
> No it won't.
>
> What Chris paper says is about something like:
>
> void f(int * p)
> {
> int x = *p;
>
> if(!p)
> {
> return;
> }
>
> printf("%d\n", x);
> }
>
> if p is NULL, this is an UB and the compiler can do anything.
>
Many thanks for your reply Xi.
Yes, I see, the compiler wouldn't change the order.
Jonny
