ENH: print a warning if ADD_LIBRARY( SHARED/MODULE ) is used and the target

platform doesn't support shared libraries

Alex

Modules/CMakeGenericSystem.cmake

@@ -19,6 +19,9 @@ SET(CMAKE_DL_LIBS "dl")
 SET(CMAKE_FIND_LIBRARY_PREFIXES "lib")
 SET(CMAKE_FIND_LIBRARY_SUFFIXES ".so" ".a")
 
+# basically all general purpose OSs support shared libs
+SET(CMAKE_TARGET_SUPPORTS_ONLY_STATIC_LIBS FALSE)
+
 SET (CMAKE_SKIP_RPATH "NO" CACHE BOOL
      "If set, runtime paths are not added when using shared libraries.")
 

Modules/Platform/Generic.cmake

@@ -6,3 +6,7 @@
 # about the platform. So everything has to be specified
 # in the system/compiler files ${CMAKE_SYSTEM_NAME}-<compiler_basename>.cmake
 # and/or ${CMAKE_SYSTEM_NAME}-<compiler_basename>-${CMAKE_SYSTEM_PROCESSOR}.cmake
+
+# (embedded) targets without operating system usually don't support shared libraries
+SET(CMAKE_TARGET_SUPPORTS_ONLY_STATIC_LIBS TRUE)
+

Source/cmAddLibraryCommand.cxx

@@ -77,6 +77,22 @@ bool cmAddLibraryCommand::InitialPass(std::vector<std::string> const& args)
     cmSystemTools::Message(msg.c_str() ,"Warning");
     }
 
+  /* ideally we should check whether for the linker language of the target 
+    CMAKE_${LANG}_CREATE_SHARED_LIBRARY is defined and if not default to
+    STATIC. But at this point we know only the name of the target, but not 
+    yet its linker language. */
+  if ((shared != 0) && 
+       (this->Makefile->IsOn("CMAKE_TARGET_SUPPORTS_ONLY_STATIC_LIBS")))
+    {
+    std::string msg = "ADD_LIBRARY for library ";
+    msg += args[0];
+    msg += " is used with the SHARED or MODULE option, but the target "
+        "platform supports only STATIC libraries. Building it STATIC instead. "
+        "This may lead to problems.";
+    cmSystemTools::Message(msg.c_str() ,"Warning");
+    shared = 0;
+    }
+
   std::vector<std::string> srclists;
   while (s != args.end()) 
     {