configure: Support configuring C++ compiler

Add configuration for C++ compiler in configure and Makefiles.
The C++ compiler is choosed as following:
 - ${CXX}, if it is specified.
 - ${cross_prefix}g++, if ${cross_prefix} is specified.
 - Otherwise, c++ is used.

Currently, usage of C++ language is only for access to Windows VSS
using COM+ services in qemu-guest-agent for Windows.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Micael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

configure

@@ -252,6 +252,8 @@ for opt do
   ;;
   --cc=*) CC="$optarg"
   ;;
+  --cxx=*) CXX="$optarg"
+  ;;
   --source-path=*) source_path="$optarg"
   ;;
   --cpu=*) cpu="$optarg"
@@ -282,6 +284,12 @@ else
   cc="${CC-${cross_prefix}gcc}"
 fi
 
+if test -z "${CXX}${cross_prefix}"; then
+  cxx="c++"
+else
+  cxx="${CXX-${cross_prefix}g++}"
+fi
+
 ar="${AR-${cross_prefix}ar}"
 as="${AS-${cross_prefix}as}"
 cpp="${CPP-$cc -E}"
@@ -626,6 +634,8 @@ for opt do
   ;;
   --host-cc=*) host_cc="$optarg"
   ;;
+  --cxx=*)
+  ;;
   --objcc=*) objcc="$optarg"
   ;;
   --make=*) make="$optarg"
@@ -1032,6 +1042,7 @@ echo "  --cross-prefix=PREFIX    use PREFIX for compile tools [$cross_prefix]"
 echo "  --cc=CC                  use C compiler CC [$cc]"
 echo "  --host-cc=CC             use C compiler CC [$host_cc] for code run at"
 echo "                           build time"
+echo "  --cxx=CXX                use C++ compiler CXX [$cxx]"
 echo "  --objcc=OBJCC            use Objective-C compiler OBJCC [$objcc]"
 echo "  --extra-cflags=CFLAGS    append extra C compiler flags QEMU_CFLAGS"
 echo "  --extra-ldflags=LDFLAGS  append extra linker flags LDFLAGS"
@@ -3561,6 +3572,7 @@ fi
 echo "Source path       $source_path"
 echo "C compiler        $cc"
 echo "Host C compiler   $host_cc"
+echo "C++ compiler      $cxx"
 echo "Objective-C compiler $objcc"
 echo "CFLAGS            $CFLAGS"
 echo "QEMU_CFLAGS       $QEMU_CFLAGS"
@@ -4148,6 +4160,7 @@ echo "PYTHON=$python" >> $config_host_mak
 echo "CC=$cc" >> $config_host_mak
 echo "CC_I386=$cc_i386" >> $config_host_mak
 echo "HOST_CC=$host_cc" >> $config_host_mak
+echo "CXX=$cxx" >> $config_host_mak
 echo "OBJCC=$objcc" >> $config_host_mak
 echo "AR=$ar" >> $config_host_mak
 echo "AS=$as" >> $config_host_mak

rules.mak

@@ -8,9 +8,13 @@ MAKEFLAGS += -rR
 %.d:
 %.h:
 %.c:
+%.cpp:
 %.m:
 %.mak:
 
+# Flags for C++ compilation
+QEMU_CXXFLAGS = -D__STDC_LIMIT_MACROS $(filter-out -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Wold-style-declaration -Wold-style-definition -Wredundant-decls, $(QEMU_CFLAGS))
+
 # Flags for dependency generation
 QEMU_DGFLAGS += -MMD -MP -MT $@ -MF $(*D)/$(*F).d
 
@@ -50,6 +54,9 @@ endif
 %.o: %.asm
 	$(call quiet-command,$(AS) $(ASFLAGS) -o $@ $<,"  AS    $(TARGET_DIR)$@")
 
+%.o: %.cpp
+	$(call quiet-command,$(CXX) $(QEMU_INCLUDES) $(QEMU_CXXFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) -c -o $@ $<,"  CXX   $(TARGET_DIR)$@")
+
 %.o: %.m
 	$(call quiet-command,$(OBJCC) $(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) -c -o $@ $<,"  OBJC  $(TARGET_DIR)$@")
 
@@ -70,7 +77,7 @@ quiet-command = $(if $(V),$1,$(if $(2),@echo $2 && $1, @$1))
 cc-option = $(if $(shell $(CC) $1 $2 -S -o /dev/null -xc /dev/null \
               >/dev/null 2>&1 && echo OK), $2, $3)
 
-VPATH_SUFFIXES = %.c %.h %.S %.m %.mak %.texi %.sh %.rc
+VPATH_SUFFIXES = %.c %.h %.S %.cpp %.m %.mak %.texi %.sh %.rc
 set-vpath = $(if $1,$(foreach PATTERN,$(VPATH_SUFFIXES),$(eval vpath $(PATTERN) $1)))
 
 # find-in-path