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

["Michael S. Tsirkin" <mst@redhat.com>]

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 <ehabkost@redhat.com>
> ---
>  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?

>    supported_os="yes"
>    libudev="yes"
>  ;;
> -- 
> 2.24.1