[PATCH] libxl/build: print a pretty message if flex/bison are needed but not found

[Roger Pau Monne <roger.pau@citrix.com>]

This patchs adds better support for both Flex and Bison, which might be needed
to compile libxl. Now configure script sets BISON and FLEX Makefile vars if
bison and flex are found, but doesn't complain if they are not found.

Also, added some Makefile soccery to print a nice error message if Bison or Flex
are needed but not found.

Please run autogen after applying this patch.

Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Cc: zhihao wang <accept.acm@gmail.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
---
 tools/configure.ac   |    2 ++
 tools/libxl/Makefile |   16 ++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/tools/configure.ac b/tools/configure.ac
index 3da0c82..8ccdc92 100644
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -75,6 +75,8 @@ AC_PROG_CC
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
 AC_PROG_INSTALL
+AC_PATH_PROG([BISON], [bison])
+AC_PATH_PROG([FLEX], [flex])
 AX_PATH_PROG_OR_FAIL([PERL], [perl])
 AS_IF([test "x$xapi" = "xy"], [
     AX_PATH_PROG_OR_FAIL([CURL], [curl-config])
diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index ac8b810..e8ec8e9 100644
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -48,6 +48,18 @@ please check libxl_linux.c and libxl_netbsd.c to see how to get it ported)
 endif
 endif
 
+ifeq ($(FLEX),)
+%.c %.h:: %.l
+	$(error Flex is needed to compile libxl, please install it and rerun \
+	configure)
+endif
+
+ifeq ($(BISON),)
+%.c %.h:: %.y
+	$(error Bison is needed to compile libxl, please install it an rerun \
+	configure)
+endif
+
 LIBXL_LIBS += -lyajl
 
 LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
@@ -83,11 +95,11 @@ all: $(CLIENTS) libxenlight.so libxenlight.a libxlutil.so libxlutil.a \
 
 $(LIBXL_OBJS) $(LIBXLU_OBJS) $(XL_OBJS): $(AUTOINCS)
 
-%.c %.h: %.y
+%.c %.h:: %.y
 	@rm -f $*.[ch]
 	$(BISON) --output=$*.c $<
 
-%.c %.h: %.l
+%.c %.h:: %.l
 	@rm -f $*.[ch]
 	$(FLEX) --header-file=$*.h --outfile=$*.c $<
 
-- 
1.7.7.5 (Apple Git-26)