make: switch from -I to -iquote

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.

To fix, switch to -iquote which is supported by both
gcc and clang and only affects #include "" directives.

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>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>

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

configure

@@ -419,7 +419,7 @@ QEMU_CFLAGS="-fPIC -fno-strict-aliasing -fno-common -fwrapv $QEMU_CFLAGS"
 QEMU_CFLAGS="-Wall -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 $QEMU_CFLAGS"
-QEMU_INCLUDES="-I. -I\$(SRC_PATH) -I\$(SRC_PATH)/include"
+QEMU_INCLUDES="-iquote . -iquote \$(SRC_PATH) -iquote \$(SRC_PATH)/include"
 if test "$debug_info" = "yes"; then
     CFLAGS="-g $CFLAGS"
     LDFLAGS="-g $LDFLAGS"
@@ -6048,19 +6048,19 @@ if test "$pthread_setname_np" = "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

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)
 
 # Include PANDA headers.
 QEMU_INCLUDES += -I$(SRC_PATH)/panda/include