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Re: [build, lto] Only accept -fuse-linker-plugin if linker supports -plugin (PR lto/46944)
Richard Guenther <rguenther@suse.de> writes:
>> > Can we to fix 46944 change the dejagnu require-linker-plugin
>> > to check if a linker plugin is used by default and not add
>> > -fuse-linker-plugin?
>>
>> That might be involved since it requires parsing gcc -Wl,-debug output.
>> I suppose the solution outlined above is simpler and thus more robust.
>
> It might be as simple as
>
> int res;
> int main() { int x; asm ("mov res, %0" : x(g)); return x; }
>
> which should fail to link with the plugin only (but yes, requies
> target dependent assembly ...).
... which I'd consider far too complicated/hard to maintain to consider.
> Or, use -save-temps and check for the existence of the resolution
> file for int main() {}. It should be named t.res for gcc -o t t.c -flto.
Only with -save-temps, otherwise it's some random file in /var/tmp. But
even so the file is removed immediately.
And even if we decide to fix PR lto/46944 like this, we're still left
with the problem of users invoking gcc with -fuse-linker-plugin and
getting either strange errors or no effect instead of a clear
diagnostic.
Rainer
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Rainer Orth, Center for Biotechnology, Bielefeld University