On Wed, Jan 23, 2013 at 4:50 PM, Ramana Radhakrishnan <ramra...@arm.com> wrote: > On 01/23/13 15:36, Richard Biener wrote: >> >> On Tue, Jan 22, 2013 at 5:00 PM, Ramana Radhakrishnan <ramra...@arm.com> >> wrote: >>> >>> Hi, >>> >>> I ran into PR driver/47785 when doing some testing with an option passed >>> to >>> the testsuite and I chose to fix this by putting out COLLECT_AS_OPTIONS >>> as >>> though these are options for the driver by prepending them with a "'-Wa", >>> and suffixing them with a "'" character and additionally providing spaces >>> as >>> duly required. I've chosen a simple implementation. >>> >>> Tested in the past with x86_64-linux-gnu and arm-none-eabi cross tests >>> (with >>> an additional -Wa option passed to the default flags in a site.exp) >>> >>> Thoughts ? >>> >>> Ok for trunk now or should I stage this for 4.9 ? >> >> >> I don't think this fix will work reliably - it's probably desirable >> anyway for other uses >> of -Wa,... but providing a symbol definition is something that needs >> to be understood >> by LTO at WPA time, otherwise we will get confusing / wrong symbol >> resolutions and >> eventually wrong code generated in the end. Thus with the patch you get >> some >> false sense of security I think (consider -fno-fat-lto-objects, you'd >> get x UNDEFed, >> and with -ffat-lto-objects you'd get a prevailing IRONLY def but the >> symbol wasn't >> in the LTO symbol table and we don't find a prevailing definition at >> WPA time ...) > > > Can you define a symbol on the command line for the assembler ? I didn't > know GAS or assemblers could do that and even if it did, I don't understand > why ... > > The linker allows you a -Wl,--defsym=foo=<val> or whatever you want to do > there, so even if the assembler were to have an undef reference to a symbol > in an object file, it would get fixed up at link time by the linker. > > So if you are saying that we need to make LTO handle -Wl, > --defsym=sym=<value> I'd envisage the need to handle potential confusion but > even that's a separate patch and unrelated to this one ...... :) > > Intrigued :)
Well, if you look at the testcase you added with your patch you see -Wa,--defsym=x=42, so the answer is yes. Richard. > cheers, > Ramana > >
