JDK 9 build with GCC 6.1.1

[Andrew Haley]

On 27/06/16 21:43, David Holmes wrote:
> 
> Okay. So I know I was initially surprised we have code that can do:
> 
> a->foo();
> 
> when a is NULL, but that is because it is actually compiled as:
> 
> foo(a);

Yes, it is.

> IIRC foo() has a "if (this != NULL)" check internally.

It doesn't, unless you write it in the body of foo().

> I'm kind of surprised that the compiler itself seems to think a->foo()  
> implies a is not NULL.

That's what the standard says, and it's what GCC does.

> I also hope it either is extremely smart about this or else very  
> conservative. Would want it to make a mess of this:
> 
> if (init(&a) != NULL) {
>    a->foo();
> }
> else {
>    log(...);
> }
> if (a)
>    a->bar();

This isn't enough to prove that a is non-null, so GCC won't eliminate
the test.

Andrew.