[PATCH] D64579: [clang-shlib] Fix clang-shlib for PRIVATE dependencies

[Shoaib Meenai via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL365825: [clang-shlib] Fix clang-shlib for PRIVATE dependencies (authored by smeenai, committed by ).
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Changed prior to commit:
  https://reviews.llvm.org/D64579?vs=209283&id=209336#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64579/new/

https://reviews.llvm.org/D64579

Files:
  cfe/trunk/tools/clang-shlib/CMakeLists.txt


Index: cfe/trunk/tools/clang-shlib/CMakeLists.txt
===================================================================
--- cfe/trunk/tools/clang-shlib/CMakeLists.txt
+++ cfe/trunk/tools/clang-shlib/CMakeLists.txt
@@ -7,8 +7,35 @@
 
 foreach (lib ${clang_libs})
   list(APPEND _OBJECTS $<TARGET_OBJECTS:obj.${lib}>)
-  list(APPEND _DEPS $<TARGET_PROPERTY:${lib},INTERFACE_LINK_LIBRARIES>)
-  list(APPEND _DEPS $<TARGET_PROPERTY:${lib},LINK_LIBRARIES>)
+  # Use the static library for its dependencies. The objects that constitute the
+  # static library will appear on the link line before the library, so it'll
+  # just be ignored, but the dependencies of the library will still be linked
+  # correctly.
+  #
+  # We could propagate the dependencies manually using the library's
+  # INTERFACE_LINK_LIBRARIES property, but that will contain $<LINK_ONLY:...>
+  # generator expressions if a static library has a private dependency, so we
+  # can't use a $<TARGET_PROPERTY:...> generator expression to get the property
+  # (since it wouldn't evaluate any generator expressions inside the property).
+  # We could use get_property and do string manipulation to manually evaluate
+  # the $<LINK_ONLY:...>, but that would miss any dependencies added after we
+  # evaluate the get_property. We could also use the LINK_LIBRARIES property
+  # instead, which should be free of any generator expressions, but that's
+  # technically incorrect (it'd most likely work fine in practice, but still).
+  #
+  # Another alternative would be to use --whole-archive or equivalent instead of
+  # using the object library at all. However, CMake reorders static libraries on
+  # the link line so that a library appears after all its dependents, which can
+  # reorder static libraries out of their --whole-archive --no-whole-archive
+  # sandwich. It's really hard to avoid that reordering while still propagating
+  # dependencies, which defeats the whole point.
+  #
+  # The ideal solution here is to bump our minimum CMake requirement to 3.12,
+  # which adds support for dependencies on object libraries. Until then, linking
+  # both the object and the static libraries seems like the least bad solution.
+  #
+  # TODO: Rework this when we bump our minimum CMake version to 3.12 or newer.
+  list(APPEND _DEPS ${lib})
 endforeach ()
 
 add_clang_library(clang_shared


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