Re: [Xen-devel] [PATCH v3] tools: detect appropriate debug optimization level

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Feb 23, 2018 at 11:26:17PM -0600, Doug Goldstein wrote:
> On 4/28/16 12:40 PM, Wei Liu wrote:
> > On Tue, Apr 26, 2016 at 09:38:45AM -0500, Doug Goldstein wrote:
> >> When building debug use -Og as the optimization level if its available,
> >> otherwise retain the use of -O0. -Og has been added by GCC to enable all
> >> optimizations that to not affect debugging while retaining full
> >> debugability.
> >>
> >> Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>
> >> ---
> >> change since v2:
> >> - switch back to cc-option-add to not call cc-option on every invocation
> >> change since v1:
> >> - switch to cc-option to only specify -O0 if -Og isn't supported
> >> ---
> >>  tools/Rules.mk | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/tools/Rules.mk b/tools/Rules.mk
> >> index 9ef0b47..1b79a6e 100644
> >> --- a/tools/Rules.mk
> >> +++ b/tools/Rules.mk
> >> @@ -138,6 +138,7 @@ SHLIB_libxenvchan  = $(SHDEPS_libxenvchan) 
> >> -Wl,-rpath-link=$(XEN_LIBVCHAN)
> >>  ifeq ($(debug),y)
> >>  # Disable optimizations and enable debugging information for macros
> >>  CFLAGS += -O0 -g3
> >> +$(call cc-option-add,CFLAGS,CC,-Og)

Though -Og will supersede -O0 because it comes later, I would rather you
use cc-option to selectively add one of the two, like:

CFLAGS += $(cc-option,CC,-Og,-O0)

Wei.

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