On Fri, May 8, 2026 at 4:56 PM Georg-Johann Lay <[email protected]> wrote:
>
> Am 08.05.26 um 11:53 schrieb Richard Biener:
> > On Thu, May 7, 2026 at 2:36 PM Georg-Johann Lay <[email protected]> wrote:
> >>
> >> This patch fixes -mno-call-main which did not work with LTO.
> >>
> >> Instead of emitting .global __call_main + __call_main=0 in some
> >> module, it uses a %{mno-call-main: --defsym __call_main=0} spec.
> >>
> >> The problem with the old implementation is that avr_no_call_main_p was
> >> set by cc1[plus] (in avr_insert_attributes) but used by lto1 (in
> >> avr_file_end).
> >> The new approach uses --defsym __call_main=0 in order to avoid link
> >> fails due to multiple definitions of __call_main in *.o and lib<mcu>.a.
> >
> > In the patch the avr.opt and the avr_insert_attributes hunk shouldn't
> > be necessary?
>
> The avr.opt change is according to
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125194#c1
>
> Some avr_insert_attributes hunk is needed because avr_no_call_main_p
> has been removed, since it is no more needed.
>
> And I added "used" to main because otherwise, LTO optimized out main.
>
> > That said, even w/o the patch the LTRANS invocations with -flto
> > should see -mno-call-main, but avr_insert_attributes might not
> > be called at LTO time.
>
> That's not a problem imho. The hook just adds section(".init9")
> and used, and they will survive as attributes.
>
> > So if in avr_file_end you check
> > avropt_call_main instead of avr_no_call_main_p you should
> > get the .global emitted. Of course in every LTRANS object,
> > but I suppose the linker should merge multiple defs?
>
> Like mentioned, I am getting multiple symbol definitions error
> from ld when emitting .global __call_main=0. Therefore, I
> switched to --defsym __call_main=0 which works fine.
OK. Another solution might have been to make the symbol
weak?
Having a testcase in the testsuite would be nice btw.
Richard.
> Johann
>
> >> This is for trunk. If you agree, I would also packport it.
> >>
> >> Johann
> >>
> >> --
> >>
> >> AVR: target/125194 - Make -mno-call-main work with -flto.
> >>
> >> Instead of emitting .global __call_main + __call_main=0 in some module,
> >> use a %{mno-call-main: --defsym __call_main=0} spec.
> >>
> >> The problem with the old implementation is that avr_no_call_main_p was set
> >> by cc1[plus] (in avr_insert_attributes) but used by lto1 (in avr_file_end).
> >> The new approach uses --defsym __call_main=0 in order to avoid link
> >> fails due to multiple definitions of __call_main in *.o and lib<mcu>.a.
> >>
> >> PR target/125194
> >> gcc/
> >> * config/avr/avr.cc (avr_no_call_main_p): Remove variable...
> >> (avr_file_end): ...and code that uses it.
> >> (avr_insert_attributes): Same. Add "used" to main attributes
> >> when -mno-call-main.
> >> * config/avr/avr.opt (-mcall-main): Add Save option flag.
> >> * config/avr/gen-avr-mmcu-specs.cc (print_mcu): Emit code
> >> for link_no_call_main specs.
> >> * config/avr/specs.h (LINK_SPEC): Add %(link_no_call_main).
>
