[xen staging] libxl: Generate golang bindings in libxl Makefile

[patchbot@xxxxxxx]

commit 60db5da62ac051aab0b217fa2d96acca1cd3ca3e
Author:     George Dunlap <george.dunlap@xxxxxxxxxx>
AuthorDate: Thu May 28 12:20:53 2020 +0100
Commit:     George Dunlap <george.dunlap@xxxxxxxxxx>
CommitDate: Thu May 28 12:20:53 2020 +0100

    libxl: Generate golang bindings in libxl Makefile
    
    The generated golang bindings (types.gen.go and helpers.gen.go) are
    left checked in so that they can be fetched from xenbits using the
    golang tooling.  This means that they must be updated whenever
    libxl_types.idl (or other dependencies) are updated.  However, the
    golang bindings are only built optionally; we can't assume that anyone
    updating libxl_types.idl will also descend into the tools/golang tree
    to re-generate the bindings.
    
    Fix this by re-generating the golang bindings from the libxl Makefile
    when the IDL dependencies are updated, so that anyone who updates
    libxl_types.idl will also end up updating the golang generated files
    as well.
    
     - Make a variable for the generated files, and a target in
       xenlight/Makefile which will only re-generate the files.
    
     - Add a target in libxl/Makefile to call external idl generation
       targets (currently only golang).
    
    For ease of testing, also add a specific target in libxl/Makefile just
    to check and update files generated from the IDL.
    
    This does mean that there are two potential paths for generating the
    files during a parallel build; but that shouldn't be an issue, since
    tools/golang/xenlight should never be built until after tools/libxl
    has completed building anyway.
    
    Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Reviewed-by: Nick Rosbrook <rosbrookn@xxxxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/golang/xenlight/Makefile | 11 ++++++++++-
 tools/libxl/Makefile           | 17 ++++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/tools/golang/xenlight/Makefile b/tools/golang/xenlight/Makefile
index cd0a62505f..8ab4cb5665 100644
--- a/tools/golang/xenlight/Makefile
+++ b/tools/golang/xenlight/Makefile
@@ -17,12 +17,21 @@ all: build
 .PHONY: package
 package: $(XEN_GOPATH)$(GOXL_PKG_DIR)
 
-$(XEN_GOPATH)/src/$(XEN_GOCODE_URL)/xenlight/: xenlight.go types.gen.go 
helpers.gen.go
+GOXL_GEN_FILES = types.gen.go helpers.gen.go
+
+$(XEN_GOPATH)/src/$(XEN_GOCODE_URL)/xenlight/: xenlight.go $(GOXL_GEN_FILES)
        $(INSTALL_DIR) $(XEN_GOPATH)$(GOXL_PKG_DIR)
        $(INSTALL_DATA) xenlight.go $(XEN_GOPATH)$(GOXL_PKG_DIR)
        $(INSTALL_DATA) types.gen.go $(XEN_GOPATH)$(GOXL_PKG_DIR)
        $(INSTALL_DATA) helpers.gen.go $(XEN_GOPATH)$(GOXL_PKG_DIR)
 
+# NOTE: This target is called from libxl/Makefile:all.  Since that
+# target must finish before golang/Makefile is called, this is
+# currently safe.  It must not be called from anywhere else in the
+# Makefile system without careful thought about races with
+# xenlight/Makefile:all
+idl-gen: $(GOXL_GEN_FILES)
+
 %.gen.go: gengotypes.py $(LIBXL_SRC_DIR)/libxl_types.idl 
$(LIBXL_SRC_DIR)/idl.py
        XEN_ROOT=$(XEN_ROOT) $(PYTHON) gengotypes.py 
$(LIBXL_SRC_DIR)/libxl_types.idl
 
diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index 69fcf21577..947eb6036e 100644
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -218,7 +218,7 @@ testidl.c: libxl_types.idl gentest.py libxl.h $(AUTOINCS)
 .PHONY: all
 all: $(CLIENTS) $(TEST_PROGS) $(PKG_CONFIG) $(PKG_CONFIG_LOCAL) \
                libxenlight.so libxenlight.a libxlutil.so libxlutil.a \
-       $(AUTOSRCS) $(AUTOINCS)
+       $(AUTOSRCS) $(AUTOINCS) idl-external
 
 $(LIBXL_OBJS) $(LIBXLU_OBJS) $(SAVE_HELPER_OBJS) \
                $(LIBXL_TEST_OBJS) $(TEST_PROG_OBJS): \
@@ -274,6 +274,21 @@ _libxl_type%.h _libxl_type%_json.h _libxl_type%_private.h 
_libxl_type%.c: libxl_
        $(call 
move-if-changed,__libxl_type$(stem)_json.h,_libxl_type$(stem)_json.h)
        $(call move-if-changed,__libxl_type$(stem).c,_libxl_type$(stem).c)
 
+# NOTE: This is safe to do at the moment because idl-external and
+# idl-gen are only called from libxl/Makefile:all, which must return
+# before golang/Makefile is callid.  idl-external and idl-gen must
+# never be called from another part of the make system without careful thought
+# about races with tools/golang/xenlight/Makefile:all
+.PHONY: idl-external
+idl-external:
+       $(MAKE) -C $(XEN_ROOT)/tools/golang/xenlight idl-gen
+
+LIBXL_IDLGEN_FILES = _libxl_types.h _libxl_types_json.h _libxl_types_private.h 
_libxl_types.c \
+       _libxl_types_internal.h _libxl_types_internal_json.h 
_libxl_types_internal_private.h _libxl_types_internal.c
+
+
+idl-gen: $(LIBXL_GEN_FILES) idl-external
+
 libxenlight.so: libxenlight.so.$(MAJOR)
        $(SYMLINK_SHLIB) $< $@
 
--
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