Re: [Xen-devel] Implementaiton of cc-option in Config.mk

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Mar 15, 2018 at 05:29:39AM -0600, Jan Beulich wrote:
> >>> On 15.03.18 at 12:22, <wei.liu2@xxxxxxxxxx> wrote:
> > On Thu, Mar 15, 2018 at 02:45:15AM -0600, Jan Beulich wrote:
> >> >>> On 14.03.18 at 18:11, <wei.liu2@xxxxxxxxxx> wrote:
> >> > The implementation of cc-option (grepping the option being tested in
> >> > output) in Config.mk now makes it not possible to detect if -Og is
> >> > supported because "-Og" doesn't appear in the output if it is not
> >> > supported. I suspect there will be other options that cc-option can't 
> >> > work
> >> > with.
> >> > 
> >> > It is implemented like that because we try to detect -Wno-* option. But
> >> > why is that important? Can't we just ignore -Wno-* if they aren't
> >> > supported?
> >> 
> >> Well, the explanation for its behavior is given in the comment
> >> next to its definition:
> > 
> > Yeah, I know that. I'm just not sure why nonexistent -Wno-* should be
> > rejected. If there is no corresponding -W* option in the first place,
> > -Wno-* shouldn't cause any difference in the end result.
> 
> The problem is that at least some compiler versions error on unknown
> -Wno-* the first time they produce some (other) warning. Hence we
> can't blindly pass -Wno-*.
> 

Urgh, OK. Thanks for the explanation.

Wei.

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