[Xen-devel] [PATCH] Add -MP to CFLAGS along with -MMD.

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

This causes gcc (yes, and clang) to emit phony targets for each dependency.

This means that when a header file is deleted, the C files which *used*
to include it will no longer stop building with bogus out-of-date
dependencies like this:

  make[5]: *** No rule to make target
  '/home/dwmw2/git/xen/xen/include/asm/hvm/svm/amd-iommu-proto.h',
  needed by 'p2m.o'. Stop.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
 tools/Rules.mk | 2 +-
 xen/Rules.mk   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/Rules.mk b/tools/Rules.mk
index 52f47be3f8..9bac15c8d1 100644
--- a/tools/Rules.mk
+++ b/tools/Rules.mk
@@ -186,7 +186,7 @@ SHLIB_libxlutil  = $(SHDEPS_libxlutil) 
-Wl,-rpath-link=$(XEN_XLUTIL)
 CFLAGS += -D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__
 
 # Get gcc to generate the dependencies for us.
-CFLAGS += -MMD -MF .$(if $(filter-out .,$(@D)),$(subst /,@,$(@D))@)$(@F).d
+CFLAGS += -MMD -MP -MF .$(if $(filter-out .,$(@D)),$(subst /,@,$(@D))@)$(@F).d
 DEPS = .*.d
 
 ifneq ($(FILE_OFFSET_BITS),)
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 92a13ca601..9079df7978 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -71,7 +71,7 @@ AFLAGS += -D__ASSEMBLY__
 ALL_OBJS := $(ALL_OBJS-y)
 
 # Get gcc to generate the dependencies for us.
-CFLAGS-y += -MMD -MF $(@D)/.$(@F).d
+CFLAGS-y += -MMD -MP -MF $(@D)/.$(@F).d
 
 CFLAGS += $(CFLAGS-y)
 # allow extra CFLAGS externally via EXTRA_CFLAGS_XEN_CORE

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