gbuild: introduce plugin + loader concepts

This introduces two concepts: a plugin and its loader (library)

LO currrently has dependency cycles for some libraries. There is
scui, which depends on sc, while sc dlopen's scui. There are the
various vclplug_*, i18npool plugins, filters/gie, acc, etc.

Usually these plugins link to their loader library, because they
use its symbols. But as a result there is no sensible way to
express the runtime dependency of loaders on the plugins.

In GNU libtool plugins are called modules and they are implemented
in an IMHO more sensible way by allowing missing symbols at link
time. This way you can have a dependency from the loader library
to its plugins, as the plugins don't depend on the loader, but you
lose the link time detection of missing symbols.

While this is in theory possible in LO too, LO currently has
plugins, like acc (accessibility), loaded by tk (toolkit), which
depends on svt (svtools), which itself depends on tk, so dropping
the tk dependency for acc on its own doesn't help :-(

And while the dependency of the plugins on their loader is fine
for the shared / DYNLOADING build, for the "static" builds you
must (somehow) link the plugins into the executables.

I also codeified a few rules into the build system along with it:
* just plugins are allowed to depend / link other plugins
* plugins aren't allowed to be linked into the merge lib
* plugin loaders are "limited" to libraries

At the high level, this is implemented via new gbuild calls:
* gb_Library_set_plugin_for,lib,loader: declare a library to be a
plugin of a loader library and add a dependeny from the plugin
library to the loader library
* gb_Library_set_plugin_for_nodep,lib,loader: ^^^^ without adding
the library dependeny
* gb_Helper_register_plugins_for_install: "plugin" replacement for
gb_Helper_register_libraries_for_install to implement some
additional checks in the build system

In the end this patch just adds a bit syntactic sugar and nothing
changes for any build.

Change-Id: I7b01d9c384cbc5838bd2cc93aff18e4868939d6e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/126163
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

3 files changed, 65 insertions, 2 deletions

diff --git a/solenv/gbuild/Helper.mk b/solenv/gbuild/Helper.mk
index 4d2fdd698005..9f3e92e02ec4 100644
--- a/solenv/gbuild/Helper.mk
+++ b/solenv/gbuild/Helper.mk
@@ -199,6 +199,13 @@ $(if $(filter UNOVERLIBS RTVERLIBS,$(1)),\
 
 endef
 
+# a plugin is a library, why can't be dynamically linked and must be dlopen'd, but must be linked static
+define gb_Helper_register_plugins_for_install
+$(call gb_Helper_register_libraries_for_install,$(1),$(2),$(3))
+gb_Library_KNOWNPLUGINS += $(3)
+
+endef
+
 define gb_Helper__register_jars
 $(foreach group,$(gb_Jar_VALIDGROUPS),\
  $(foreach target,$(2),\
diff --git a/solenv/gbuild/Library.mk b/solenv/gbuild/Library.mk
index 6562cbf41d34..2fb98bcf622f 100644
--- a/solenv/gbuild/Library.mk
+++ b/solenv/gbuild/Library.mk
@@ -172,6 +172,23 @@ gb_Library__COMPONENTPREFIXES := \
 gb_Library_get_runtime_filename = $(call gb_Library_get_filename,$(1))
 gb_Library_get_runtime_filename_for_build = $(call gb_Library_get_filename_for_build,$(1))
 
+# instead of setting nodep use gb_Library_set_plugin_for_nodep
+#
+# call gb_Library_set_plugin_for,library,loader,nodep
+define gb_Library_set_plugin_for
+ifneq (,$$(filter-out $(gb_Library_KNOWNPLUGINS),$(1)))
+$$(eval $$(call gb_Output_info,currently known plugins are: $(sort $(gb_Library_KNOWNPLUGINS)),ALL))
+$$(eval $$(call gb_Output_error,Unknown plugin(s) '$$(filter-out $(gb_Library_KNOWNPLUGINS),$(1)))'. Plugins must be registered in Repository.mk or RepositoryExternal.mk))
+endif
+
+$(call gb_LinkTarget_get_target,$(call gb_Library_get_linktarget,$(2))) : PLUGINS += $(1)
+$(eval $(call gb_LinkTarget__add_plugin,$(call gb_Library_get_linktarget,$(2)),$(1)))
+$(eval $(call gb_LinkTarget__set_plugin_for,$(call gb_Library_get_linktarget,$(1)),$(2),$(3)))
+endef
+
+# call gb_Library_set_plugin_for_nodep,library,loader
+gb_Library_set_plugin_for_nodep = $(call gb_Library_set_plugin_for,$(1),$(2),$(true))
+
 # forward the call to the gb_LinkTarget implementation
 # (note: because the function name is in $(1), the other args are shifted by 1)
 define gb_Library__forward_to_Linktarget
@@ -182,7 +199,6 @@ endef
 # copy pasta for forwarding: this could be (and was) done more elegantly, but
 # these here can be found by both git grep and ctags
 gb_Library_add_cobject = $(call gb_Library__forward_to_Linktarget,$(0),$(1),$(2),$(3))
-gb_Library_add_cobject = $(call gb_Library__forward_to_Linktarget,$(0),$(1),$(2),$(3))
 gb_Library_add_cobjects = $(call gb_Library__forward_to_Linktarget,$(0),$(1),$(2),$(3))
 gb_Library_add_cxxobject = $(call gb_Library__forward_to_Linktarget,$(0),$(1),$(2),$(3))
 gb_Library_add_cxxobjects = $(call gb_Library__forward_to_Linktarget,$(0),$(1),$(2),$(3))
diff --git a/solenv/gbuild/LinkTarget.mk b/solenv/gbuild/LinkTarget.mk
index 783f6022abe6..a5306eeb38b9 100644
--- a/solenv/gbuild/LinkTarget.mk
+++ b/solenv/gbuild/LinkTarget.mk
@@ -1225,6 +1225,7 @@ ifeq ($(DISABLE_DYNLOADING),)
 $(call gb_LinkTarget_get_target,$(1)) : \
 	$(foreach lib,$(3),$(call gb_Library_get_exports_target,$(lib)))
 endif
+
 $(call gb_LinkTarget_get_headers_target,$(1)) : \
 	$(foreach lib,$(2),$(call gb_Library_get_headers_target,$(lib)))
 $(foreach lib,$(2),$(call gb_LinkTarget__lib_dummy_depend,$(lib)))
@@ -1273,7 +1274,12 @@ endef
 define gb_LinkTarget_use_libraries
 ifneq (,$$(filter-out $(gb_Library_KNOWNLIBS),$(2)))
 $$(eval $$(call gb_Output_info,currently known libraries are: $(sort $(gb_Library_KNOWNLIBS)),ALL))
-$$(eval $$(call gb_Output_error,Cannot link against library/libraries $$(filter-out $(gb_Library_KNOWNLIBS),$(2)). Libraries must be registered in Repository.mk or RepositoryExternal.mk))
+$$(eval $$(call gb_Output_error,Cannot link against library/libraries '$$(filter-out $(gb_Library_KNOWNLIBS),$(2))'. Libraries must be registered in Repository.mk or RepositoryExternal.mk))
+endif
+ifneq (,$$(filter $(2),$(gb_Library_KNOWNPLUGINS)))
+ifneq (,$$(filter $(1),$$(foreach plugin,$(gb_Library_KNOWNPLUGINS),$(call gb_Library__get_workdir_linktargetname,$(plugin)))))
+$$(eval $$(call gb_Output_error,Cannot link against plugin library/libraries '$$(filter $(2),$(gb_Library_KNOWNPLUGINS))'. Only plugins are allowed to do that.))
+endif
 endif
 
 ifeq ($(call gb_LinkTarget__is_build_tool,$(1)),$(true))
@@ -2102,4 +2108,38 @@ endif
 
 endef
 
+gb_LinkTarget__get_plugins_var = $(call gb_LinkTarget__get_workdir_linktargetname,$(1))<>PLUGINS
+gb_LinkTarget__get_plugins = $($(call gb_LinkTarget__get_plugins_var,$(1)))
+gb_Library__get_plugins = $($(call gb_LinkTarget__get_plugins_var,$(call gb_Library_get_linktarget,$(1))))
+
+define gb_LinkTarget__add_plugin
+$(call gb_LinkTarget__get_plugins_var,$(1)) += $(2)
+
+endef
+
+# Instead of setting nodep use gb_LinkTarget__set_plugin_for_nodep
+#
+# call gb_LinkTarget__set_plugin_for,linktarget,loader,nodep
+define gb_LinkTarget__set_plugin_for
+ifneq (,$$(filter-out $(gb_Library_KNOWNLIBS),$(2)))
+$$(eval $$(call gb_Output_info,currently known libraries are: $(sort $(gb_Library_KNOWNLIBS)),ALL))
+$$(eval $$(call gb_Output_error,Cannot link against library/libraries $$(filter-out $(gb_Library_KNOWNLIBS),$(2)). Libraries must be registered in Repository.mk or RepositoryExternal.mk))
+endif
+ifeq (,$(filter $(1),$(foreach plugin,$(gb_Library_KNOWNPLUGINS),$(call gb_Library_get_linktarget,$(plugin)))))
+$$(eval $$(call gb_Output_error,Unknown plugin(s) '$(filter $(1),$(foreach plugin,$(gb_Library_KNOWNPLUGINS),$(call gb_Library_get_linktarget,$(plugin))))'. Plugins must be registered in Repository.mk or RepositoryExternal.mk))
+endif
+ifneq (,$(filter $(1),$(foreach lib,$(gb_MERGEDLIBS),$(call gb_Library_get_linktarget,$(lib)))))
+$$(eval $$(call gb_Output_error,Plugins can't be in mergelibs))
+endif
+ifeq ($(call gb_LinkTarget__is_build_tool,$(1)),$(true))
+$$(eval $$(call gb_Output_error,Plugin support for build tools not implemented))
+endif
+
+$(if $(3),,$(call gb_LinkTarget__use_libraries,$(1),$(2),$(2)))
+
+endef
+
+# call gb_LinkTarget__set_plugin_for_nodep,linktarget,loader
+gb_LinkTarget__set_plugin_for_nodep = $(call gb_LinkTarget__set_plugin_for,$(1),$(2),$(true))
+
 # vim: set noet sw=4: