ENH: Added target property ENABLE_EXPORTS for executable targets. It enables the executables for linking by loadable modules that import symbols from the executable. This finishes the executable import library support mentioned in bug #4210.

4 files changed, 48 insertions, 5 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 71d3c51..c7f50f6 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1659,9 +1659,19 @@ void cmLocalGenerator
       {
       // Compute the proper name to use to link this library.
       cmTarget* tgt = this->GlobalGenerator->FindTarget(0, lib.c_str());
-      if(tgt && (tgt->GetType() == cmTarget::STATIC_LIBRARY ||
-                 tgt->GetType() == cmTarget::SHARED_LIBRARY ||
-                 tgt->GetType() == cmTarget::MODULE_LIBRARY))
+      bool impexe = (tgt &&
+                     tgt->GetType() == cmTarget::EXECUTABLE &&
+                     tgt->GetPropertyAsBool("ENABLE_EXPORTS"));
+      if(impexe && !implib)
+        {
+        // Skip linking to executables on platforms with no import
+        // libraries.
+        continue;
+        }
+      else if(tgt && (tgt->GetType() == cmTarget::STATIC_LIBRARY ||
+                      tgt->GetType() == cmTarget::SHARED_LIBRARY ||
+                      tgt->GetType() == cmTarget::MODULE_LIBRARY ||
+                      impexe))
         {
         // This is a CMake target.  Ask the target for its real name.
         // Pass the full path to the target file but purposely leave
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 78b44a4..e5dc29b 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -944,13 +944,16 @@ void cmMakefile::AddLinkLibraryForTarget(const char *target,
         }
       // if it is not a static or shared library then you can not link to it
       if(!((tgt->GetType() == cmTarget::STATIC_LIBRARY) ||
-           (tgt->GetType() == cmTarget::SHARED_LIBRARY)))
+           (tgt->GetType() == cmTarget::SHARED_LIBRARY) ||
+           (tgt->GetType() == cmTarget::EXECUTABLE &&
+            tgt->GetPropertyAsBool("ENABLE_EXPORTS"))))
         {
         cmOStringStream e;
         e << "Attempt to add link target " << lib << " of type: "
           << cmTarget::TargetTypeNames[static_cast<int>(tgt->GetType())]
           << "\nto target " << target
-          << ". You can only link to STATIC or SHARED libraries.";
+          << ". One can only link to STATIC or SHARED libraries, or "
+          << "to executables with the ENABLE_EXPORTS property set.";
         // in older versions of cmake linking to modules was allowed
         if( tgt->GetType() == cmTarget::MODULE_LIBRARY )
           {
diff --git a/Source/cmMakefileExecutableTargetGenerator.cxx b/Source/cmMakefileExecutableTargetGenerator.cxx
index 2414458..48aa284 100644
--- a/Source/cmMakefileExecutableTargetGenerator.cxx
+++ b/Source/cmMakefileExecutableTargetGenerator.cxx
@@ -347,6 +347,19 @@ void cmMakefileExecutableTargetGenerator::WriteExecutableRule(bool relink)
   std::string linkRule =
     this->Makefile->GetRequiredDefinition(linkRuleVar.c_str());
   cmSystemTools::ExpandListArgument(linkRule, commands1);
+  if(this->Target->GetPropertyAsBool("ENABLE_EXPORTS"))
+    {
+    // If a separate rule for creating an import library is specified
+    // add it now.
+    std::string implibRuleVar = "CMAKE_";
+    implibRuleVar += linkLanguage;
+    implibRuleVar += "_CREATE_IMPORT_LIBRARY";
+    if(const char* rule =
+       this->Makefile->GetDefinition(implibRuleVar.c_str()))
+      {
+      cmSystemTools::ExpandListArgument(rule, commands1);
+      }
+    }
   this->LocalGenerator->CreateCDCommand
     (commands1,
      this->Makefile->GetStartOutputDirectory(),
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index ef4a07e..441269c 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -259,6 +259,23 @@ void cmTarget::DefineProperties(cmake *cm)
      "how the executable will be linked.");
 
   cm->DefineProperty
+    ("ENABLE_EXPORTS", cmProperty::TARGET,
+     "Specify whether an executable exports symbols for loadable modules.",
+     "Normally an executable does not export any symbols because it is "
+     "the final program.  It is possible for an executable to export "
+     "symbols to be used by loadable modules.  When this property is "
+     "set to true CMake will allow other targets to \"link\" to the "
+     "executable with the TARGET_LINK_LIBRARIES command.  "
+     "On all platforms a target-level dependency on the executable is "
+     "created for targets that link to it.  "
+     "For non-DLL platforms the link rule is simply ignored since "
+     "the dynamic loader will automatically bind symbols when the "
+     "module is loaded.  "
+     "For DLL platforms an import library will be created for the "
+     "exported symbols and then used for linking.  "
+     "All Windows-based systems including Cygwin are DLL platforms.");
+
+  cm->DefineProperty
     ("OBJECT_FILES", cmProperty::TARGET, 
      "Used to get the resulting list of object files that make up a "
      "target.",