Re: [Xen-devel] [PATCH] tools: work around collision of -O0 and -D_FORTIFY_SOURCE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.02.15 at 00:33, <dslutz@xxxxxxxxxxx> wrote:
> On 02/04/15 12:01, Jan Beulich wrote:
>> The former gets enforced by our debug builds, the latter appears to be
>> not uncommon for certain distros' Python packages. Newer glibc warns on
>> uses of _FORTIFY_SOURCE without optimization being enabled, which with
>> -Werror causes the build to fail.
>> 
>> Determine Python's intended flags to be passed to the C compiler via
>> "python-config --cflags", and replace -O0 by -O1 when a non-zero value
>> gets set for _FORTIFY_SOURCE.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Well, this does not fix debug=y builds for me:
> [...]
> gcc -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions

Where is this -Wp,-D_FORTIFY_SOURCE=2 coming from? Is
python-config producing this? The patch provided certainly doesn't
deal with that case.

> Using this change:
> 
> dcs-xen-54:~/xen-master>git show | cat
> commit 3cda306a162e55d73c25efc14840e7afeec8d3d3
> Author: Don Slutz <dslutz@xxxxxxxxxxx>
> Date:   Wed Feb 4 17:57:00 2015 -0500
> 
>     tools/Rules.mk: Drop -O0 for debug=y
> 
>     This is a partial revert of
> 
>     commit 1166ecf781b1016eaa61f8d5ba4fb1fde9d599b6
>     Author: Euan Harris <euan.harris@xxxxxxxxxx>
>     Date:   Mon Dec 1 14:21:05 2014 +0000
> 
>         tools/Rules.mk: Don't optimize debug builds; add macro debugging
> information
> 
>     Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> 
> diff --git a/tools/Rules.mk b/tools/Rules.mk
> index 74cf37e..8bf603d 100644
> --- a/tools/Rules.mk
> +++ b/tools/Rules.mk
> @@ -56,7 +56,7 @@ SHLIB_libxenvchan  = -Wl,-rpath-link=$(XEN_LIBVCHAN)
> 
>  ifeq ($(debug),y)
>  # Disable optimizations and enable debugging information for macros
> -CFLAGS += -O0 -g3
> +CFLAGS += -g3
>  endif
> 
>  LIBXL_BLKTAP ?= $(CONFIG_BLKTAP2)
> 
> 
> I can now build with "debug=y" on Fedora 17.

If you went through the earlier discussion, you'd have seen that
this was already rejected as a possible fix.

Jan


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