Re: [Xen-devel] [PATCH] xen: Don't use -nostdinc flags with CLANG

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.02.14 at 00:29, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> Commit 06a9c7e "xen: move -nostdinc into common Rules.mk." breaks
> compilation with clang:
> 
> In file included from sched_sedf.c:8:
> In file included from /home/julieng/works/xen/xen/include/xen/lib.h:5:
> /home/julieng/works/xen/xen/include/xen/stdarg.h:20:12: error: 'stdarg.h' 
> file
> not found with <angled> include; use "quotes" instead
>            ^~~~~~~~~~
>            "stdarg.h"
> In file included from sched_sedf.c:8:
> /home/julieng/works/xen/xen/include/xen/lib.h:101:63: error: unknown type 
> name 'va_list'
> extern int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
>                                                               ^
> /home/julieng/works/xen/xen/include/xen/lib.h:105:64: error: unknown type 
> name 'va_list'
> extern int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
> 
> I have the same errors on different version of clang:
>     - clang 3.0 on debian wheezy
>     - clang 3.3 on Fedora 20
>     - clang 3.5 build from trunk
> 
> Removing -nostdinc fix the build on clang.

But does this also do the right thing? I.e. I doubt you're immune
then against picking up headers you don't want to include in a
hypervisor build, or properly failing if - for whatever reason, e.g.
during development after having made a mistake - a header can't
be found in the paths we want the compiler to look for them, but
can be found in a "standard" include directory.

IOW I think it first needs to be understood/explained why and by
how much clang behavior differs here.

Jan

> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/Rules.mk | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/Rules.mk b/xen/Rules.mk
> index df1428f..ed9b8d0 100644
> --- a/xen/Rules.mk
> +++ b/xen/Rules.mk
> @@ -46,7 +46,8 @@ CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
>  CFLAGS += -pipe -g -D__XEN__ -include $(BASEDIR)/include/xen/config.h
>  # Solaris puts stdarg.h &c in the system include directory.
>  ifneq ($(XEN_OS),SunOS)
> -CFLAGS += -nostdinc -iwithprefix include
> +CFLAGS-y        += -iwithprefix include
> +CFLAGS-$(gcc)   += -nostdinc
>  endif
>  
>  CFLAGS-$(XSM_ENABLE)    += -DXSM_ENABLE
> -- 
> 1.8.5.3
> 
> 
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> http://lists.xen.org/xen-devel 




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