[PATCH v2] libxl/build: print a warning if flex/bison are needed

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

This patch 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 warning message if
Bison or Flex are needed but not found.

Please run autogen after applying this patch.

Changes since v1:

 * Print a warning message instead of an error if flex/bison are
   needed but not found.

Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Cc: Ian Jackson <Ian.Jackson@eu.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 250dffd..47becfe 100644
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -77,6 +77,8 @@ 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 0ac43bd..13de15d 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
+	$(warning Flex is needed to compile libxl, please install it and rerun \
+	configure)
+endif
+
+ifeq ($(BISON),)
+%.c %.h:: %.y
+	$(warning 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)