at: lt: document, fix extra DESTDIR ref

1 files changed, 38 insertions, 2 deletions

diff --git a/build-aux/Makefile.once.head/10-lt.mk b/build-aux/Makefile.once.head/10-lt.mk
index 355a5b4343..2841bfe214 100644
--- a/build-aux/Makefile.once.head/10-lt.mk
+++ b/build-aux/Makefile.once.head/10-lt.mk
@@ -1,13 +1,49 @@
 mod.lt.description = (systemd) Easy handling of libtool dependencies
-mod.lt.deps += files quote
+mod.lt.depends += files
+define mod.lt.doc
+# Inputs:
+#   - Global variable    : `$(.LIBPATTERNS)`
+#   - Directory variable : `$(files.sys)`
+#   - Target variable    : `$@`
+#   - Target variable    : `$(@F)`
+#   - Target variable    : `$^`
+# Outputs:
+#   - Target variable : `lt.lib.rpath`     (`$(@D)`, `$(files.sys)`)
+#   - Target variable : `lt.lib.files.all` (`$^`, `$(.LIBPATTERNS)`)
+#   - Target variable : `lt.lib.files.ld`  (`$(lt.lib.rpath)`, `$(lt.lib.files.all)`)
+#   - Target variable : `lt.lib.post`      (`$(lt.lib.rpath)`, `$(lt.lib.files.all)`)
+#   - Target variable : `lt.exe.files.all` (`$^`, `$(.LIBPATTERNS)`)
+#   - Target variable : `lt.exe.files.ld`  (an alias for `lt.exe.files.all`)
+#
+# A set of variables to make interacting with libtool a little easier.
+#
+# libtool tries to abstract away the difference between static libraries
+# and dynamic libraries.  But, it does a crappy job.  If one library
+# depends on another library, you have to care about which of them are
+# static and which are dynamic, or you'll either end up with missing
+# symbols, or duplicate symbols.  Either way, it will fail to link your
+# executable.
+#
+# So, our workaround: don't pass any .la libraries to libtool/ld when
+# linking a convenience library, but then run a post-libtool command to
+# insert them into the .la file's dependency_libs. This uses the
+# emptiness of lt.lib.rpath to determine if a library is a static
+# convenience library or not.
+endef
+mod.lt.doc := $(value mod.lt.doc)
 
 _lt.patsubst-all = $(if $1,$(call _lt.patsubst-all,$(wordlist 2,$(words $1),$1),$2,$(patsubst $(firstword $1),$2,$3)),$3)
 _lt.unLIBPATTERNS = $(foreach _lt.tmp,$1,$(if $(filter $(.LIBPATTERNS),$(notdir $(_lt.tmp))),$(call _lt.patsubst-all,$(.LIBPATTERNS),-l%,$(notdir $(_lt.tmp))),$(_lt.tmp)))
 _lt.rest = $(wordlist 2,$(words $1),$1)
+# Usage: $(call _lt.dedup,ITEM1 ITEM2 ITEM3)
+# Removes duplicate items while keeping the order the same (the leftmost of a duplicate is used).
 _lt.dedup = $(if $1,$(if $(filter $(firstword $1),$(call _lt.rest,$1)),,$(firstword $1) )$(call _lt.dedup,$(call _lt.rest,$1)))
+# Usage: $(call _lt.dependency_libs,LIB1.la OBJ.lo LIB2.la)
+#        => LIB1.la LIB1.la:dependency_libs OBJ.lo LIB2.la LIB2.la:dependency_libs
+# Insert a .la library's dependency_libs after the library itself in the list.
 _lt.dependency_libs = $(foreach _lt.tmp,$1,$(_lt.tmp)$(if $(filter %.la,$(_lt.tmp)), $(shell . $(_lt.tmp); echo $$dependency_libs)))
 
- lt.lib.rpath     = $(dir $(patsubst $(DESTDIR)%,%,$(filter %/$(@F),$(files.sys))))
+ lt.lib.rpath     = $(dir $(filter %/$(@F),$(files.sys))
  lt.lib.files.all = $(filter %.lo %.la -l%,$(call _lt.unLIBPATTERNS,$^))
  lt.lib.files.ld  = $(strip $(if $(lt.lib.rpath),\
                                  $(lt.lib.files.all),\