[tlbuild] Compiling asy with recent gcc

[Ken Brown]

On 3/5/2020 5:48 PM, Karl Berry wrote:
>      If I build without optimization, the problem doesn't occur.
> 
> Doesn't that imply a compiler bug?

Probably, but it can also be caused by programming errors.  For example, if a 
pointer is dereferenced without a null check, the optimizer can assume it's not 
null and delete later null checks.  This happens if the 
-fdelete-null-pointer-checks option is enabled, which it is by default when 
optimizing with -O2 or -O3.

Unfortunately, doesn't explain the crash I found, which happens even with -O1. 
Moreover, the crash occurs at the first dereference, and there are no null 
pointer checks to delete.

> Good luck reporting it :(. -k

I won't even try without a better reproducer.

Ken