From d24279c6d6f83dbb41859a0f4bb95ab5595128e5 Mon Sep 17 00:00:00 2001
From: kervala <devnull@localhost>
Date: Sat, 2 Oct 2010 14:21:45 +0200
Subject: [PATCH] Changed: #1111 Create a CMake macro to check if we should
 link to an external lib or not

---
 code/CMakeModules/CheckDepends.cmake | 103 +++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 code/CMakeModules/CheckDepends.cmake

diff --git a/code/CMakeModules/CheckDepends.cmake b/code/CMakeModules/CheckDepends.cmake
new file mode 100644
index 000000000..be90e271e
--- /dev/null
+++ b/code/CMakeModules/CheckDepends.cmake
@@ -0,0 +1,103 @@
+# Macros to check if a library needs to be manually linked to another one
+# because it's using a symbol from it but it's not linked to
+#
+# Syntax:
+# CHECK_DEPENDS(MYLIBRARY OTHERLIBRARY SYMBOL MUSTLINK)
+#
+# Sets the following variables:
+#   XYZ_LIBRARY_MUSTLINK
+#
+# Example:
+# Check if we need to explicitly link to libz with libpng
+# CHECK_DEPENDS(PNG_LIBRARY ZLIB_LIBRARY inflate)
+# objdump -p /usr/lib/libwwwxml.so | grep expat
+# objdump -T /usr/lib/libwwwxml.so | grep "*UND*" | grep XML_ParserCreate
+# objdump -p <lib> | grep <libray>
+# objdump -T <lib> | grep "*UND*" | grep <function>
+#
+
+# CHECK_UNDEFINED_SYMBOL
+# Macro to check if a library is calling an undefined symbol
+#
+# Syntax:
+# CHECK_UNDEFINED_SYMBOL(MYLIBRARY SYMBOL SYMBOL_FOUND)
+# SYMBOL_FOUND will be set to TRUE or FALSE
+#
+# Example:
+# CHECK_UNDEFINED_SYMBOL(PNG_LIBRARY inflate INFLATE_FOUND)
+#
+MACRO(CHECK_UNDEFINED_SYMBOL MYLIBRARY SYMBOL SYMBOL_FOUND)
+  SET(${SYMBOL_FOUND} TRUE)
+  IF(WIN32)
+    # Always TRUE under Windows because we are using static libraries
+  ELSEIF(APPLE)
+    # TODO: use otool to detect if a library is using a symbol
+  ELSEIF(UNIX)
+    IF(CMAKE_OBJDUMP)
+      # Use objdump to check if a library is using an external symbol
+      EXEC_PROGRAM(${CMAKE_OBJDUMP} ARGS "-T ${MYLIBRARY} | grep ${SYMBOL}" OUTPUT_VARIABLE OBJDUMP_SYMBOL)
+      message(STATUS "OBJDUMP_SYMBOL = ${OBJDUMP_SYMBOL}")
+      IF(NOT OBJDUMP_SYMBOL MATCHES "UND")
+        SET(${SYMBOL_FOUND} FALSE)
+      ENDIF(OBJDUMP_SYMBOL MATCHES "UND")
+    ENDIF(CMAKE_OBJDUMP)
+  ENDIF(WIN32)
+ENDMACRO(CHECK_UNDEFINED_SYMBOL)
+
+MACRO(CHECK_LINKED_LIBRARY MYLIBRARY OTHERLIBRARY LIBRARY_FOUND)
+  SET(${LIBRARY_FOUND} FALSE)
+  IF(WIN32)
+    # Always FALSE under Windows because we are using static libraries
+  ELSEIF(APPLE)
+    # TODO: use otool to detect if a library is using a symbol
+  ELSEIF(UNIX)
+    IF(CMAKE_OBJDUMP)
+      # Use objdump to check if a library is linked to another library
+      EXEC_PROGRAM(${CMAKE_OBJDUMP} ARGS "-p ${MYLIBRARY} | grep ${OTHERLIBRARY}" OUTPUT_VARIABLE OBJDUMP_LIBRARY)
+      IF(OBJDUMP_LIBRARY MATCHES "NEEDED")
+        SET(${LIBRARY_FOUND} TRUE)
+      ENDIF(OBJDUMP_LIBRARY MATCHES "NEEDED")
+    ENDIF(CMAKE_OBJDUMP)
+  ENDIF(WIN32)
+ENDMACRO(CHECK_LINKED_LIBRARY)
+
+MACRO(CHECK_DEPENDS MYLIBRARY OTHERLIBRARY SYMBOL MUSTLINK)
+  CHECK_UNDEFINED_SYMBOL(MYLIBRARY SYMBOL SYMBOL_FOUND)
+
+  IF(SYMBOL_FOUND)
+    CHECK_LINKED_LIBRARY(MYLIBRARY OTHERLIBRARY LIBRARY_FOUND)
+  ENDIF(SYMBOL_FOUND)
+
+  IF(SYMBOL_FOUND AND NOT LIBRARY_FOUND)
+    SET(${MUSTLINK} YES)
+  ELSE(SYMBOL_FOUND AND NOT LIBRARY_FOUND)
+    SET(${MUSTLINK} NO)
+  ENDIF(SYMBOL_FOUND AND NOT LIBRARY_FOUND)
+ENDMACRO(CHECK_DEPENDS)
+
+MACRO(LINK_DEPENDS LIBRARIES MYLIBRARY OTHERLIBRARY SYMBOL)
+  SET(MUST_LINK FALSE)
+  IF(${MYLIBRARY} AND ${OTHERLIBRARY} AND NOT ${OTHERLIBRARY}_LINKED)
+    IF(WIN32 OR WITH_STATIC)
+      # In static, we link all libraries because it will keep only used symbols
+      SET(MUST_LINK TRUE)
+    ELSE(WIN32 OR WITH_STATIC)
+      CHECK_UNDEFINED_SYMBOL(${MYLIBRARY} ${SYMBOL} SYMBOL_FOUND)
+
+      IF(SYMBOL_FOUND)
+        CHECK_LINKED_LIBRARY(${MYLIBRARY} ${OTHERLIBRARY} LIBRARY_FOUND)
+      ENDIF(SYMBOL_FOUND)
+
+#      CHECK_DEPENDS(${MYLIBRARY} ${${OTHERLIBRARY}} ${SYMBOL} MUST_LINK)
+      IF(SYMBOL_FOUND AND NOT LIBRARY_FOUND)
+        MESSAGE(STATUS "Underlinking found: ${${MYLIBRARY}} needs ${${OTHERLIBRARY}} but is not linked to, manually linking...")
+        SET(MUST_LINK TRUE)
+      ENDIF(SYMBOL_FOUND AND NOT LIBRARY_FOUND)
+    ENDIF(WIN32 OR WITH_STATIC)
+  ENDIF(${MYLIBRARY} AND ${OTHERLIBRARY} AND NOT ${OTHERLIBRARY}_LINKED)
+  IF(MUST_LINK)
+    MESSAGE(STATUS "Linking with ${${OTHERLIBRARY}}")
+    SET(${OTHERLIBRARY}_LINKED TRUE)
+    SET(${LIBRARIES} ${${LIBRARIES}} ${${OTHERLIBRARY}})
+  ENDIF(MUST_LINK)
+ENDMACRO(LINK_DEPENDS)