Re: [Qemu-devel] [PATCH for-2.12 2/2] make: switch from -I to -iquote

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

On Wed, Mar 21, 2018 at 03:36:51PM +0000, Daniel P. Berrangé wrote:
> On Wed, Mar 21, 2018 at 05:22:07PM +0200, Michael S. Tsirkin wrote:
> > Our rule right now is to use <> for external headers,
> > "" for internal ones. The idea was to avoid conflicts
> > between e.g. a system file named <trace.h> and an
> > internal one by the same name.
> > 
> > Unfortunately we use -I compiler flag so it does not
> > help: a system file doing #include <trace.h> will
> > still pick up ours first.
> 
> Has that actually hit you practice ?  I'm wondering if this
> is just theoretical in which case it could wait till 2.13
> since this scenario has existed in QEMU along time, or
> a real problem right now requiring fix in 2.12.

It's borderline.

In particular there is at least one instance where we already have a
conflict (yes, there are probably other ways to address this, but
I consider them less robust):

util/getauxval.c:#include <sys/auxv.h>
/usr/include/sys/auxv.h:#include <elf.h>

So it really does build by luck.


> > To fix, switch to -iquote which is supported by both
> > gcc and clang and only affects #include "" directives.
> 
> Fine since we don't support anything other than
> gcc and clang. I'm assuming -iquote has been supported
> by these two compilers for a long time though ? The GCC
> docs annoyingly don't ever mention what release features
> appear in :-(

Judging by git log output:

For clang it appears to be there since 2007 that's pretty
close to day 1.

gcc's log is better documented, it's been there since 2004-05-03

> > 
> > As a side effect, this catches any future uses of
> >  #include <> for internal headers.
> > 
> > Suggested-by: Stefan Weil <sw@weilnetz.de>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Thanks!

> 
> > 
> > I still think we want to switch to a more formal rule such as qemu/
> > prefix for all includes down the road, but this will at least catch any
> > scheme violations from creeping in meanwhile.
> > 
> > 
> >  configure       | 16 ++++++++--------
> >  rules.mak       |  2 +-
> >  Makefile.target |  4 ++--
> >  3 files changed, 11 insertions(+), 11 deletions(-)
> > 
> > diff --git a/configure b/configure
> > index af72fc8..23a4f3b 100755
> > --- a/configure
> > +++ b/configure
> > @@ -534,7 +534,7 @@ QEMU_CFLAGS="-fno-strict-aliasing -fno-common -fwrapv $QEMU_CFLAGS"
> >  QEMU_CFLAGS="-Wall -Wundef -Wwrite-strings -Wmissing-prototypes $QEMU_CFLAGS"
> >  QEMU_CFLAGS="-Wstrict-prototypes -Wredundant-decls $QEMU_CFLAGS"
> >  QEMU_CFLAGS="-D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE $QEMU_CFLAGS"
> > -QEMU_INCLUDES="-I. -I\$(SRC_PATH) -I\$(SRC_PATH)/accel/tcg -I\$(SRC_PATH)/include"
> > +QEMU_INCLUDES="-iquote . -iquote \$(SRC_PATH) -iquote \$(SRC_PATH)/accel/tcg -iquote \$(SRC_PATH)/include"
> >  if test "$debug_info" = "yes"; then
> >      CFLAGS="-g $CFLAGS"
> >      LDFLAGS="-g $LDFLAGS"
> > @@ -6560,19 +6560,19 @@ if test "$vxhs" = "yes" ; then
> >  fi
> >  
> >  if test "$tcg_interpreter" = "yes"; then
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/tci $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/tci $QEMU_INCLUDES"
> >  elif test "$ARCH" = "sparc64" ; then
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/sparc $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/sparc $QEMU_INCLUDES"
> >  elif test "$ARCH" = "s390x" ; then
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/s390 $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/s390 $QEMU_INCLUDES"
> >  elif test "$ARCH" = "x86_64" -o "$ARCH" = "x32" ; then
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/i386 $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/i386 $QEMU_INCLUDES"
> >  elif test "$ARCH" = "ppc64" ; then
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/ppc $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/ppc $QEMU_INCLUDES"
> >  else
> > -  QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/\$(ARCH) $QEMU_INCLUDES"
> > +  QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/\$(ARCH) $QEMU_INCLUDES"
> >  fi
> > -QEMU_INCLUDES="-I\$(SRC_PATH)/tcg $QEMU_INCLUDES"
> > +QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg $QEMU_INCLUDES"
> >  
> >  echo "TOOLS=$tools" >> $config_host_mak
> >  echo "ROMS=$roms" >> $config_host_mak
> > diff --git a/rules.mak b/rules.mak
> > index 6e94333..93a0702 100644
> > --- a/rules.mak
> > +++ b/rules.mak
> > @@ -29,7 +29,7 @@ QEMU_DGFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d
> >  # dir, one absolute and the other relative to the compiler working
> >  # directory. These are the same for target-independent files, but
> >  # different for target-dependent ones.
> > -QEMU_LOCAL_INCLUDES = -I$(BUILD_DIR)/$(@D) -I$(@D)
> > +QEMU_LOCAL_INCLUDES = -iquote $(BUILD_DIR)/$(@D) -iquote $(@D)
> >  
> >  WL_U := -Wl,-u,
> >  find-symbols = $(if $1, $(sort $(shell $(NM) -P -g $1 | $2)))
> > diff --git a/Makefile.target b/Makefile.target
> > index 6549481..d0ec77a 100644
> > --- a/Makefile.target
> > +++ b/Makefile.target
> > @@ -11,9 +11,9 @@ $(call set-vpath, $(SRC_PATH):$(BUILD_DIR))
> >  ifdef CONFIG_LINUX
> >  QEMU_CFLAGS += -I../linux-headers
> >  endif
> > -QEMU_CFLAGS += -I.. -I$(SRC_PATH)/target/$(TARGET_BASE_ARCH) -DNEED_CPU_H
> > +QEMU_CFLAGS += -iquote .. -iquote $(SRC_PATH)/target/$(TARGET_BASE_ARCH) -DNEED_CPU_H
> >  
> > -QEMU_CFLAGS+=-I$(SRC_PATH)/include
> > +QEMU_CFLAGS+=-iquote $(SRC_PATH)/include
> >  
> >  ifdef CONFIG_USER_ONLY
> >  # user emulator name
> > -- 
> > MST
> > 
> 
> Regards,
> Daniel
> -- 
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