Re: [PATCH 1/2] Use -isystem for linux-headers dir

[Eduardo Habkost]

On Wed, Mar 11, 2020 at 07:05:45PM -0400, Michael S. Tsirkin wrote:
> On Wed, Mar 11, 2020 at 06:51:29PM -0400, Eduardo Habkost wrote:
> > glibc and Linux-provided headers are known to generate macro
> > redefinition warnings when used together.  For example:
> > <linux/mman.h> and <sys/mman.h> duplicate some macro definitions.
> > 
> > We normally never see those warnings because GCC suppresses
> > warnings generated by system headers.  We carry our own copy of
> > Linux header files, though, and this makes those warnings not be
> > suppressed when glibc headers are included before Linux headers
> > (e.g. if <sys/mman.h> is included before <linux/mman.h>).
> > 
> > Use -isystem instead of -I for linux-headers.  This makes the
> > compiler treat our linux-headers directory the same way it treats
> > system-provided Linux headers, and suppress warnings generated by
> > them.
> > 
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  Makefile.target | 2 +-
> >  configure       | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Makefile.target b/Makefile.target
> > index 2d43dc586a..934a9f7431 100644
> > --- a/Makefile.target
> > +++ b/Makefile.target
> > @@ -12,7 +12,7 @@ endif
> >  
> >  $(call set-vpath, $(SRC_PATH):$(BUILD_DIR))
> >  ifdef CONFIG_LINUX
> > -QEMU_CFLAGS += -I../linux-headers
> > +QEMU_CFLAGS += -isystem ../linux-headers
> >  endif
> >  QEMU_CFLAGS += -iquote .. -iquote $(SRC_PATH)/target/$(TARGET_BASE_ARCH) 
> > -DNEED_CPU_H
> >  
> > diff --git a/configure b/configure
> > index cbf864bff1..04a2a7f2dd 100755
> > --- a/configure
> > +++ b/configure
> > @@ -899,7 +899,7 @@ Linux)
> >    linux="yes"
> >    linux_user="yes"
> >    kvm="yes"
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/linux-headers -I$PWD/linux-headers 
> > $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-isystem \$(SRC_PATH)/linux-headers -I$PWD/linux-headers 
> > $QEMU_INCLUDES"
> 
> Shouldn't both be -isystem?

I haven't noticed we had both.

This line looks weird, does anybody know why we have
$PWD/linux-headers here?

-- 
Eduardo