build: automatically handle GIT submodule checkout for dtc

Currently if DTC is required by configure and not available in the host
OS install, we exit with an error message telling the user to checkout a
git submodule or install the library.

This introduces automatic handling of the git submodule checkout process
and enables it for dtc. This only runs if building from GIT, so users of
release tarballs still need the system library install. The current state
of the git checkout is stashed in .git-submodule-status, and a helper
program is used to determine if this state matches the desired submodule
state. A dependency against 'Makefile' ensures that the submodule state
is refreshed at the start of the build process

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170929101201.21039-2-berrange@redhat.com

[ kraxel: use /bin/sh not bash for scripts/git-submodule.sh ]
[ kraxel: fix Makefile dependencies ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

[fixup] Makefile dep

.gitignore

@@ -113,6 +113,7 @@
 /docs/version.texi
 *.tps
 .stgit-*
+.git-submodule-status
 cscope.*
 tags
 TAGS

MAINTAINERS

@@ -1949,3 +1949,9 @@ M: Daniel P. Berrange <berrange@redhat.com>
 S: Odd Fixes
 F: docs/devel/build-system.txt
 
+Build System
+------------
+GIT submodules
+M: Daniel P. Berrange <berrange@redhat.com>
+S: Odd Fixes
+F: scripts/git-submodule.sh

Makefile

@@ -14,6 +14,27 @@ ifneq ($(wildcard config-host.mak),)
 all:
 include config-host.mak
 
+git-submodule-update:
+
+.PHONY: git-submodule-update
+
+ifeq (0,$(MAKELEVEL))
+  git_module_status := $(shell \
+    cd '$(SRC_PATH)' && \
+    ./scripts/git-submodule.sh status $(GIT_SUBMODULES); \
+    echo $$?; \
+  )
+
+ifeq (1,$(git_module_status))
+git-submodule-update:
+	$(call quiet-command, \
+          (cd $(SRC_PATH) && ./scripts/git-submodule.sh update $(GIT_SUBMODULES)), \
+          "GIT","$(GIT_SUBMODULES)")
+endif
+endif
+
+.git-submodule-status: git-submodule-update
+
 # Check that we're not trying to do an out-of-tree build from
 # a tree that's been used for an in-tree build.
 ifneq ($(realpath $(SRC_PATH)),$(realpath .))
@@ -84,6 +105,7 @@ endif
 GENERATED_FILES += $(TRACE_HEADERS)
 GENERATED_FILES += $(TRACE_SOURCES)
 GENERATED_FILES += $(BUILD_DIR)/trace-events-all
+GENERATED_FILES += .git-submodule-status
 
 trace-group-name = $(shell dirname $1 | sed -e 's/[^a-zA-Z0-9]/_/g')
 
@@ -330,7 +352,7 @@ DTC_MAKE_ARGS=-I$(SRC_PATH)/dtc VPATH=$(SRC_PATH)/dtc -C dtc V="$(V)" LIBFDT_src
 DTC_CFLAGS=$(CFLAGS) $(QEMU_CFLAGS)
 DTC_CPPFLAGS=-I$(BUILD_DIR)/dtc -I$(SRC_PATH)/dtc -I$(SRC_PATH)/dtc/libfdt
 
-subdir-dtc:dtc/libfdt dtc/tests
+subdir-dtc: .git-submodule-status dtc/libfdt dtc/tests
 	$(call quiet-command,$(MAKE) $(DTC_MAKE_ARGS) CPPFLAGS="$(DTC_CPPFLAGS)" CFLAGS="$(DTC_CFLAGS)" LDFLAGS="$(LDFLAGS)" ARFLAGS="$(ARFLAGS)" CC="$(CC)" AR="$(AR)" LD="$(LD)" $(SUBDIR_MAKEFLAGS) libfdt/libfdt.a,)
 
 dtc/%:

configure

@@ -264,6 +264,7 @@ cc_i386=i386-pc-linux-gnu-gcc
 libs_qga=""
 debug_info="yes"
 stack_protector=""
+git_submodules=""
 
 # Don't accept a target_list environment variable.
 unset target_list
@@ -3584,8 +3585,12 @@ EOF
   if compile_prog "" "$fdt_libs" ; then
     # system DTC is good - use it
     fdt=yes
-  elif test -d ${source_path}/dtc/libfdt ; then
-    # have submodule DTC - use it
+  else
+      # have GIT checkout, so activate dtc submodule
+      if test -e "${source_path}/.git" ; then
+          git_submodules="${git_submodules} dtc"
+      fi
+      if test -d "${source_path}/dtc/libfdt" || test -e "${source_path}/.git" ; then
           fdt=yes
           dtc_internal="yes"
           mkdir -p dtc
@@ -3596,16 +3601,15 @@ EOF
           fdt_cflags="-I\$(SRC_PATH)/dtc/libfdt"
           fdt_libs="-L\$(BUILD_DIR)/dtc/libfdt $fdt_libs"
       elif test "$fdt" = "yes" ; then
-    # have neither and want - prompt for system/submodule install
-    error_exit "DTC (libfdt) version >= 1.4.2 not present. Your options:" \
-        "  (1) Preferred: Install the DTC (libfdt) devel package" \
-        "  (2) Fetch the DTC submodule, using:" \
-        "      git submodule update --init dtc"
+          # Not a git build & no libfdt found, prompt for system install
+          error_exit "DTC (libfdt) version >= 1.4.2 not present." \
+                     "Please install the DTC (libfdt) devel package"
       else
           # don't have and don't want
           fdt_libs=
           fdt=no
       fi
+  fi
 fi
 
 libs_softmmu="$libs_softmmu $fdt_libs"
@@ -5295,6 +5299,7 @@ echo "local state directory   queried at runtime"
 echo "Windows SDK       $win_sdk"
 fi
 echo "Source path       $source_path"
+echo "GIT submodules    $git_submodules"
 echo "C compiler        $cc"
 echo "Host C compiler   $host_cc"
 echo "C++ compiler      $cxx"
@@ -5483,6 +5488,7 @@ echo "extra_cxxflags=$EXTRA_CXXFLAGS" >> $config_host_mak
 echo "extra_ldflags=$EXTRA_LDFLAGS" >> $config_host_mak
 echo "qemu_localedir=$qemu_localedir" >> $config_host_mak
 echo "libs_softmmu=$libs_softmmu" >> $config_host_mak
+echo "GIT_SUBMODULES=$git_submodules" >> $config_host_mak
 
 echo "ARCH=$ARCH" >> $config_host_mak
 

scripts/git-submodule.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+#
+# This code is licensed under the GPL version 2 or later.  See
+# the COPYING file in the top-level directory.
+
+set -e
+
+substat=".git-submodule-status"
+
+command=$1
+shift
+modules="$@"
+
+if test -z "$modules"
+then
+    test -e $substat || touch $substat
+    exit 0
+fi
+
+if ! test -e ".git"
+then
+    echo "$0: unexpectedly called with submodules but no git checkout exists"
+    exit 1
+fi
+
+case "$command" in
+status)
+    test -f "$substat" || exit 1
+    trap "rm -f ${substat}.tmp" EXIT
+    git submodule status $modules > "${substat}.tmp"
+    diff "${substat}" "${substat}.tmp" >/dev/null
+    exit $?
+    ;;
+update)
+    git submodule update --init $modules 1>/dev/null 2>&1
+    git submodule status $modules > "${substat}"
+    ;;
+esac