In tree libraries which link against other in tree libraries in a way
which is opaque to their callers need special handling, specifically
correct use of -Wl,-rpath-link for the recusively used libraries.
Currently this is rather simple, but up coming changes are going to
introduce transitive dependencies more than 1 step deep.
Introduce a SHDEPS idiom to contain all the recursive deps for a
library and include those in both LDLIBS (for linking) and SHLIB (for
recursive uses).
Try and document the whole thing.
Signed-off-by: Ian Campbell
Acked-by: Ian Jackson
---
v4: Unmanged description of libbaz.
---
tools/Rules.mk | 74 --
1 file changed, 62 insertions(+), 12 deletions(-)
diff --git a/tools/Rules.mk b/tools/Rules.mk
index 2c422bd..24dc56b 100644
--- a/tools/Rules.mk
+++ b/tools/Rules.mk
@@ -34,25 +34,72 @@ INSTALL_SHLIB = : install-shlib-unsupported-fail
SYMLINK_SHLIB = : symlink-shlib-unsupported-fail
endif
+# Compiling and linking against in tree libraries.
+#
+# In order to compile and link against an in-tree library various
+# cpp/compiler/linker options are required.
+#
+# For example consider a library "libfoo" which itself uses two other
+# libraries:
+# libbar - whose use is entirely internal to libfoo and not exposed
+# to users of libfoo at all.
+# libbaz - whose use is entirely internal to libfoo but libfoo's
+# public headers include one or more of libbaz's
+# public headers. Users of libfoo are therefore transitively
+# using libbaz's header but not linking against libbaz.
+#
+# SHDEPS_libfoo: Flags for linking recursive dependencies of
+#libfoo. Must contain SHLIB for every library which
+#libfoo links against. So must contain both
+#$(SHLIB_libbar) and $(SHLIB_libbaz).
+#
+# SHLIB_libfoo: Flags for recursively linking against libfoo. Must
+# contains SHDEPS_libfoo and:
+# -Wl,-rpath-link=
+#
+# CFLAGS_libfoo: Flags for compiling against libfoo. Must add the
+#directories containing libfoo's headers to the
+#include path. Must recursively include
+#$(CFLAGS_libbaz), to satisfy the transitive inclusion
+#of the headers but not $(CFLAGS_libbar) since none of
+#libbar's headers are required to build against
+#libfoo.
+#
+# LDLIBS_libfoo: Flags for linking against libfoo. Must contain
+#$(SHDEPS_libfoo) and the path to libfoo.so
+#
+# Consumers of libfoo should include $(CFLAGS_libfoo) and
+# $(LDLIBS_libfoo) in their appropriate directories. They should not
+# include any CFLAGS or LDLIBS relating to libbar or libbaz unless
+# they use those libraries directly (not via libfoo) too.
+#
+# Consumers of libfoo should not directly use $(SHDEPS_libfoo) or
+# $(SHLIB_libfoo)
+
CFLAGS_libxenctrl = -I$(XEN_LIBXC)/include $(CFLAGS_xeninclude)
+SHDEPS_libxenctrl =
LDLIBS_libxenctrl = $(XEN_LIBXC)/libxenctrl$(libextension)
SHLIB_libxenctrl = -Wl,-rpath-link=$(XEN_LIBXC)
CFLAGS_libxenguest = -I$(XEN_LIBXC)/include $(CFLAGS_xeninclude)
-LDLIBS_libxenguest = $(XEN_LIBXC)/libxenguest$(libextension)
-SHLIB_libxenguest = -Wl,-rpath-link=L$(XEN_LIBXC)
+SHDEPS_libxenguest =
+LDLIBS_libxenguest = $(SHDEPS_libxenguest)
$(XEN_LIBXC)/libxenguest$(libextension)
+SHLIB_libxenguest = $(SHDEPS_libxenguest) -Wl,-rpath-link=L$(XEN_LIBXC)
CFLAGS_libxenstore = -I$(XEN_XENSTORE)/include $(CFLAGS_xeninclude)
-LDLIBS_libxenstore = $(XEN_XENSTORE)/libxenstore$(libextension)
-SHLIB_libxenstore = -Wl,-rpath-link=$(XEN_XENSTORE)
+SHDEPS_libxenstore =
+LDLIBS_libxenstore = $(SHDEPS_libxenguest)
$(XEN_XENSTORE)/libxenstore$(libextension)
+SHLIB_libxenstore = $(SHDEPS_libxenguest) -Wl,-rpath-link=$(XEN_XENSTORE)
CFLAGS_libxenstat = -I$(XEN_LIBXENSTAT)
-LDLIBS_libxenstat = $(SHLIB_libxenctrl) $(SHLIB_libxenstore)
$(XEN_LIBXENSTAT)/libxenstat$(libextension)
-SHLIB_libxenstat = -Wl,-rpath-link=$(XEN_LIBXENSTAT)
+SHDEPS_libxenstat = $(SHLIB_libxenctrl) $(SHLIB_libxenstore)
+LDLIBS_libxenstat = $(SHDEPS_libxenstat)
$(XEN_LIBXENSTAT)/libxenstat$(libextension)
+SHLIB_libxenstat = $(SHDEPS_libxenstat) -Wl,-rpath-link=$(XEN_LIBXENSTAT)
CFLAGS_libxenvchan = -I$(XEN_LIBVCHAN)
-LDLIBS_libxenvchan = $(SHLIB_libxenctrl) $(SHLIB_libxenstore)
$(XEN_LIBVCHAN)/libxenvchan$(libextension)
-SHLIB_libxenvchan = -Wl,-rpath-link=$(XEN_LIBVCHAN)
+SHDEPS_libxenvchan = $(SHLIB_libxenctrl) $(SHLIB_libxenstore)
+LDLIBS_libxenvchan = $(SHDEPS_libxenvchan)
$(XEN_LIBVCHAN)/libxenvchan$(libextension)
+SHLIB_libxenvchan = $(SHDEPS_libxenvchan) -Wl,-rpath-link=$(XEN_LIBVCHAN)
ifeq ($(debug),y)
# Disable optimizations and enable debugging information for macros
@@ -65,17 +112,20 @@ LIBXL_BLKTAP ?= $(CONFIG_BLKTAP2)
ifeq ($(LIBXL_BLKTAP),y)
CFLAGS_libblktapctl = -I$(XEN_BLKTAP2)/control -I$(XEN_BLKTAP2)/include
$(CFLAGS_xeninclud
