From Alberto Luaces, "he new GNU linker, "gold", is going to replace soon the current ld in

almost all Linux distributions. Although it is 100% compatible with ld,
by default it gives an error if a library has unresolved symbols at link
time, that is, it has set -Wl,--no-undefined by default. Debian folks
have found that libosg.so and libosgDB.so use some functions belonging
to libdl.so {dlsym,dlopen,dlclose,dlerror} without linking to it.

My changes link those two libraries to libdl.so explicitly in the same
way it is already done for libm.so and librt.so."

CMakeLists.txt

@@ -152,6 +152,7 @@ IF(UNIX)
     FIND_PACKAGE(X11)
     # Some Unicies need explicit linkage to the Math library or the build fails.
     FIND_LIBRARY(MATH_LIBRARY m)
+    FIND_LIBRARY(DL_LIBRARY dl)
     IF( CMAKE_SYSTEM MATCHES "Linux" )
         FIND_LIBRARY( RT_LIBRARY rt )
     ENDIF( CMAKE_SYSTEM MATCHES "Linux" )

src/osg/CMakeLists.txt

@@ -331,7 +331,7 @@ ADD_LIBRARY(${LIB_NAME}
 LINK_INTERNAL(${LIB_NAME}     
     OpenThreads
 )
-LINK_EXTERNAL(${LIB_NAME} ${CMAKE_THREAD_LIBS_INIT}    ${MATH_LIBRARY} ${RT_LIBRARY} )
+LINK_EXTERNAL(${LIB_NAME} ${CMAKE_THREAD_LIBS_INIT}    ${MATH_LIBRARY} ${RT_LIBRARY} ${DL_LIBRARY})
 LINK_CORELIB_DEFAULT(${LIB_NAME} ${CMAKE_THREAD_LIBS_INIT} ${MATH_LIBRARY} ${RT_LIBRARY} )
 
 INCLUDE(ModuleInstall OPTIONAL)

src/osgDB/CMakeLists.txt

@@ -135,7 +135,7 @@ LINK_INTERNAL(${LIB_NAME}
     osg
     OpenThreads
 )
-LINK_EXTERNAL(${LIB_NAME} ${OSGDB_PLATFORM_SPECIFIC_LIBRARIES})
+LINK_EXTERNAL(${LIB_NAME} ${OSGDB_PLATFORM_SPECIFIC_LIBRARIES} ${DL_LIBRARY})
 LINK_WITH_VARIABLES(${LIB_NAME} ${COMPRESSION_LIBRARIES})
 LINK_CORELIB_DEFAULT(${LIB_NAME})