Re: system.h and system header include cleanup - ORTHOGONAL POINTS

["N.M. Maclaren" <nmm1 at cam dot ac dot uk>]

On Nov 27 2010, Joseph S. Myers wrote:

Thanks very much.

> I don't think anything (at least anything built for the host) in GCC, 
> whether needed for bootstrapping or not, should be using VLAs; it's the 
> combination of the two that is documented as reducing the lifetime of 
> memory from alloca when building with GCC:

I agree that using both is doubleplus ungood.  If existing code uses the
wider scope of alloca, then not using VLAs is the only sane approach.

While VLAs are much cleaner and potentially much more efficient, I think 
that the description you gave and I snipped seriously underestimates the 
problems, in general. I have seen similar combinations (in other languages) 
cause memory leaks, for example, and it wouldn't surprise me if that 
happened with some C compilers/libraries and that combination. They each 
'poison' the other.

Regards,
Nick Maclaren.