On Tue, Nov 15, 2016 at 10:47 AM, Eric Botcazou <ebotca...@adacore.com> wrote:
>> Can you verify that a TU compiled with -fstrict-aliasing will link as
>> if -fno-strict-aliasing if -fno-strict-aliasing is specified at link time?
>
> Yes, it does:
>
> eric@polaris:~/build/gcc/native> ~/install/gcc/bin/gcc -c t.c -O2 -flto
> eric@polaris:~/build/gcc/native> ~/install/gcc/bin/gcc -o t t.o -O2 -save-
> temps -fverbose-asm && grep strict-aliasing t.ltrans0.s
> # -fstore-merging -fstrict-aliasing -fstrict-overflow
> eric@polaris:~/build/gcc/native> ~/install/gcc/bin/gcc -o t t.o -O2 -fno-
> strict-aliasing -save-temps -fverbose-asm && grep strict-aliasing t.ltrans0.s
> # -fno-strict-aliasing -fverbose-asm -fltrans t.ltrans0.o
Yes, I know -fno-strict-aliasing is globally set, but will all -fstrict-aliasing
optimization attributes on functions be "overwritten"? That is, are you
sure that when optimizing a function originally compiled with -fstrict-aliasing
that -fno-strict-aliasing is in effect?
>> That said, -Wno-lto-type-mismatch can be used to disable the warning as
>> well.
>
> Right, but the wording ("code may be misoptimized") is a bit scaring so I'd
> rather avoid it when possible.
>
> --
> Eric Botcazou
