Re: [avr-gcc-list] Link Time Optimization vs __builtin_unreachable() and .signature?

[Georg-Johann Lay]

Bob Paddock schrieb:
> > Can you be more specific what you mean with "after"?
>
> Alas it is not as simple as the __builtin_unreachable when I look at
> the .map and .sym files, as I thought yesterday.
>
> A working build has this:
> Size after:
>    text    data     bss
>   66435     775    3954
>
> Build with LTO enabled has this:
> Size after:
>    text    data     bss
>   14527      88    2151
>
> LTO diff between with_lto.map and no_lto.map shows 71 sections have
> been removed:
>
> [...]
>
> Tables of strings and tables of function pointers have also been removed.
>
> If main(), and many other used functions, are being removed little
> wonder the program doesn't work with LTO.

By no means main should be optimized away, so there is evidence that
something fundamental is breaking.

Is main decorated with attributes?

> I no longer understand what LTO was meant to do (I'm sure throwing
> away vast amounts of needed code and tables was not its purpose), so
> I'll give up on it for now.
>
> If you have any interest in looking at this code, let me know and I'll
> put it on a web site for you to download.

Yes, if the project is ready to be easily rebuilt (no missing 
headers/directories, etc)