[libc++] Move the linker script generation step to CMake
Summary:
This allows the linker script generation to query CMake properties
(specifically the dependencies of libc++.so) instead of having to
carry these dependencies around manually in global variables. Notice
the removal of the LIBCXX_INTERFACE_LIBRARIES global variable.
Reviewers: phosek, EricWF
Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D68343
llvm-svn: 374116
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 1ea8bb39b9c4ec71bb53196a2cdfa001328e1cac
diff --git a/cmake/Modules/DefineLinkerScript.cmake b/cmake/Modules/DefineLinkerScript.cmake
new file mode 100644
index 0000000..2b456a4
--- /dev/null
+++ b/cmake/Modules/DefineLinkerScript.cmake
@@ -0,0 +1,50 @@
+# This function defines a linker script in place of the symlink traditionally
+# created for shared libraries.
+#
+# More specifically, this function goes through the PUBLIC and INTERFACE
+# library dependencies of <target> and gathers them into a linker script,
+# such that those libraries are linked against when the shared library for
+# <target> is linked against.
+#
+# Arguments:
+# <target>: A target representing a shared library. A linker script will be
+# created in place of that target's TARGET_LINKER_FILE, which is
+# the symlink pointing to the actual shared library (usually
+# libFoo.so pointing to libFoo.so.1, which itself points to
+# libFoo.so.1.0).
+
+function(define_linker_script target)
+ if (NOT TARGET "${target}")
+ message(FATAL_ERROR "The provided target '${target}' is not actually a target.")
+ endif()
+
+ get_target_property(target_type "${target}" TYPE)
+ if (NOT "${target_type}" STREQUAL "SHARED_LIBRARY")
+ message(FATAL_ERROR "The provided target '${target}' is not a shared library (its type is '${target_type}').")
+ endif()
+
+ set(symlink "$<TARGET_LINKER_FILE:${target}>")
+ set(soname "$<TARGET_SONAME_FILE_NAME:${target}>")
+
+ get_target_property(interface_libs "${target}" INTERFACE_LINK_LIBRARIES)
+
+ set(link_libraries)
+ if (interface_libs)
+ foreach(lib IN LISTS interface_libs)
+ if (TARGET "${lib}")
+ list(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}$<TARGET_PROPERTY:${lib},OUTPUT_NAME>")
+ else()
+ list(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}${lib}")
+ endif()
+ endforeach()
+ endif()
+ list(JOIN link_libraries " " link_libraries)
+
+ set(linker_script "INPUT(${soname} ${link_libraries})")
+ add_custom_command(TARGET "${target}" POST_BUILD
+ COMMAND "${CMAKE_COMMAND}" -E remove "${symlink}"
+ COMMAND "${CMAKE_COMMAND}" -E echo "${linker_script}" > "${symlink}"
+ COMMENT "Generating linker script: '${linker_script}' as file ${symlink}"
+ VERBATIM
+ )
+endfunction()