Re: [Xen-devel] [PATCH 2/2] tools: detect appropriate debug optimization level

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On Wed, Apr 6, 2016 at 3:07 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Doug Goldstein writes ("[PATCH 2/2] tools: detect appropriate debug 
> optimization level"):
>> The build should not use -O0 as that results in miscompilations. There
>> have been a few instances on the ML where users were told to switch
>> from -O0 to -O1 or -O2 or to set debug=n and their issue went away. The
>> preferred route should be to use -Og if its available, otherwise use
>> -O1 which is the default. This change undoes the change from -O1 to -O0
>> in 1166ecf781b1016eaa61f8d5ba4fb1fde9d599b6.
>
> To summarise: I agree with using -Og if it is available.  But I
> disagree with reverting 1166ecf7 in the case where it isn't; if -Og is
> not available, we should stick with -O0.
>
> I'm open to persuasion in the latter point but I would like specific
> examples of problems (and then I would form an opinion about the
> specific problems), not generalities.
>
> Doug, would you like to, for now, propose a patch that uses -Og if it
> is available, but otherwise falls back to -O0 ?  NB that if
> convenient, this can be done simply by always specifying -O0 and
> putting -Og after it if it is supported.

I agree that it would be good to include specific bugs that this
fixes.  Presuming that they are as described (compilation errors for
reasonable setups), I continue to think that making things compile for
everyone is more important than making them debuggable via gdb for
people running compilers that don't support -Og.

 -George

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