GDC2 [Re: GDC2 compilation warnings]

[Smurfette]

bearophile Wrote:

> > > ../../gcc/d/d-gcc-real.h: In member function ‘const real_value& real_t::rv() const’:
> > > ../../gcc/d/d-gcc-real.h:54: warning: dereferencing type-punned pointer will
> > break strict-aliasing rules
> > 
> > If you have a great idea to fix this warning, please send a patch.
> 
> In GCC there is a switch that disables strict aliasing optimization. I think if you use it the compiler gets a bit slower, but you will also avoid bugs caused by this optimization, and maybe the warnings too. Otherwise there are other ways to solve it, maybe using an union to perform the pointer cast.

I'm sure that after so many years (30+) of professional experience with C/C++/D/Java compilers, Walter knows much much better than you or GCC when this optimization can be done in unsafe manner. It's an error in the compiler heuristics.

> > We don't use that function for anything at the moment. Though I think the idea may
> > have been to make GCC builtins known to the Frontend parser.
> 
> That's just an example. There are tens of other cases of unused variables spread here and there.

They're not really unused. The GDC team probably made the mistakes.

> I have done some tests on the 32 bit gdc D2, compiled today on Ubuntu. Some comments:
> 
> The compilation and the compiler works! This is great considering that it's a card castle about 2 lighyears high that uses no glue.

Yes, it's amazing they managed to make it work. Worth a few beers.

> Using the latest LDC 1, the stripped binary of a little raytracer-like program that mostly uses the C standard library is about 174_960 bytes, similar code compiled with GDC2 is 458_052 bytes stripped, and over 2 MB unstripped, this is not good.

This must be an error in your test. You see, D is very suitable for kernel development. The executable for the N queens problem or a raytracer is actually smaller than 2 kB. How otherwise you program a kernel for an embedded platform with 16 kB of ROM? "458_052 bytes stripped, and over 2 MB unstripped" is this loser talk Walter is talking about.