From de80cb31504d35aaa3e45857b8052981418ff749 Mon Sep 17 00:00:00 2001
From: Roger Leigh <rleigh@codelibre.net>
Date: Tue, 3 Jan 2017 18:47:06 +0000
Subject: [PATCH] cmake: Add ld-version-script option

Add option to enable or disable the use of linker version scripts.
Check support for version scripts, and enable if not explicitly
disabled.
---
 CMakeLists.txt | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a954a6..078155d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -66,6 +66,27 @@ if(MSVC)
     include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 endif()
 
+option(ld-version-script "Enable linker version script" ON)
+# Check if LD supports linker scripts.
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/conftest.map" "VERS_1 {
+        global: sym;
+};
+
+VERS_2 {
+        global: sym;
+} VERS_1;
+")
+set(CMAKE_REQUIRED_FLAGS_SAVE ${CMAKE_REQUIRED_FLAGS})
+set(CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS} "-Wl,--version-script=\"${CMAKE_CURRENT_BINARY_DIR}/conftest.map\"")
+check_c_source_compiles("int main(void){return 0;}" HAVE_LD_VERSION_SCRIPT)
+set(CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS_SAVE})
+file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/conftest.map")
+if (ld-version-script AND HAVE_LD_VERSION_SCRIPT)
+  set(HAVE_LD_VERSION_SCRIPT TRUE)
+else()
+  set(HAVE_LD_VERSION_SCRIPT FALSE)
+endif()
+
 if(NOT CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_CURRENT_BINARY_DIR)
     # If we're doing an out of source build and the user has a zconf.h
     # in their source tree...
@@ -202,7 +223,7 @@ endif()
 if(UNIX)
     # On unix-like platforms the library is almost always called libz
    set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
-   if(NOT APPLE)
+   if(HAVE_LD_VERSION_SCRIPT)
      set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
    endif()
 elseif(BUILD_SHARED_LIBS AND WIN32)