INTERFACE_LIBRARY: Avoid codepaths which set unneeded properties.

As an INTERFACE_LIBRARY has no direct link dependencies, we can
short-circuit in cmGeneratorExpressionEvaluator and
in cmGlobalGenerator::CheckLocalGenerators.

As they do not generate any output directly, any generate- or install-
related code acn also be short-circuited. Many of the local generators
already do this.

Because only INTERFACE related properties make sense on INTERFACE_LIBRARY
targets, avoid setting other properties, for example via defaults.

Source/cmComputeTargetDepends.cxx

@@ -237,7 +237,15 @@ void cmComputeTargetDepends::CollectTargetDepends(int depender_index)
     it != configs.end(); ++it)
     {
     std::vector<std::string> tlibs;
+    if (depender->GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      // For INTERFACE_LIBRARY depend on the interface instead.
+      depender->GetInterfaceLinkLibraries(it->c_str(), tlibs, depender);
+      }
+    else
+      {
       depender->GetDirectLinkLibraries(it->c_str(), tlibs, depender);
+      }
     // A target should not depend on itself.
     emitted.insert(depender->GetName());
     for(std::vector<std::string>::const_iterator lib = tlibs.begin();

Source/cmExportFileGenerator.cxx

@@ -387,15 +387,12 @@ void getCompatibleInterfaceProperties(cmTarget *target,
   cmComputeLinkInformation *info = target->GetLinkInformation(config);
 
   if (!info)
-    {
-    if (target->GetType() != cmTarget::INTERFACE_LIBRARY)
     {
     cmMakefile* mf = target->GetMakefile();
     cmOStringStream e;
     e << "Exporting the target \"" << target->GetName() << "\" is not "
         "allowed since its linker language cannot be determined";
     mf->IssueMessage(cmake::FATAL_ERROR, e.str());
-      }
     return;
     }
 
@@ -447,6 +444,8 @@ void cmExportFileGenerator::PopulateCompatibleInterfaceProperties(
   getPropertyContents(target, "COMPATIBLE_INTERFACE_NUMBER_MAX",
                       ifaceProperties);
 
+  if (target->GetType() != cmTarget::INTERFACE_LIBRARY)
+    {
     getCompatibleInterfaceProperties(target, ifaceProperties, 0);
 
     std::vector<std::string> configNames;
@@ -457,6 +456,7 @@ void cmExportFileGenerator::PopulateCompatibleInterfaceProperties(
       {
       getCompatibleInterfaceProperties(target, ifaceProperties, ci->c_str());
       }
+    }
 
   for (std::set<std::string>::const_iterator it = ifaceProperties.begin();
     it != ifaceProperties.end(); ++it)

Source/cmGeneratorExpressionEvaluator.cxx

@@ -954,7 +954,8 @@ static const struct TargetPropertyNode : public cmGeneratorExpressionNode
 
     if (!prop)
       {
-      if (target->IsImported())
+      if (target->IsImported()
+          || target->GetType() == cmTarget::INTERFACE_LIBRARY)
         {
         return linkedTargetsContent;
         }

Source/cmGlobalGenerator.cxx

@@ -1309,6 +1309,11 @@ void cmGlobalGenerator::FinalizeTargetCompileInfo()
       {
       cmTarget* t = &ti->second;
 
+      if (t->GetType() == cmTarget::INTERFACE_LIBRARY)
+        {
+        continue;
+        }
+
       t->AppendBuildInterfaceIncludes();
 
       for (std::vector<cmValueWithOrigin>::const_iterator it
@@ -1461,6 +1466,10 @@ void cmGlobalGenerator::CheckLocalGenerators()
     for (cmTargets::iterator l = targets.begin();
          l != targets.end(); l++)
       {
+      if (l->second.GetType() == cmTarget::INTERFACE_LIBRARY)
+        {
+        continue;
+        }
       const cmTarget::LinkLibraryVectorType& libs =
         l->second.GetOriginalLinkLibraries();
       for(cmTarget::LinkLibraryVectorType::const_iterator lib = libs.begin();

Source/cmGlobalVisualStudio7Generator.cxx

@@ -327,6 +327,10 @@ void cmGlobalVisualStudio7Generator::WriteTargetConfigurations(
         projectTargets.begin(); tt != projectTargets.end(); ++tt)
     {
     cmTarget* target = *tt;
+    if(target->GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
     const char* expath = target->GetProperty("EXTERNAL_MSPROJECT");
     if(expath)
       {
@@ -364,6 +368,10 @@ void cmGlobalVisualStudio7Generator::WriteTargetsToSolution(
         projectTargets.begin(); tt != projectTargets.end(); ++tt)
     {
     cmTarget* target = *tt;
+    if(target->GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
     bool written = false;
 
     // handle external vc project files

Source/cmGlobalVisualStudio8Generator.cxx

@@ -442,7 +442,8 @@ bool cmGlobalVisualStudio8Generator::NeedLinkLibraryDependencies(
     {
     if(cmTarget* depTarget = this->FindTarget(0, ui->c_str()))
       {
-      if(depTarget->GetProperty("EXTERNAL_MSPROJECT"))
+      if(depTarget->GetType() != cmTarget::INTERFACE_LIBRARY
+          && depTarget->GetProperty("EXTERNAL_MSPROJECT"))
         {
         // This utility dependency names an external .vcproj target.
         // We use LinkLibraryDependencies="true" to link to it without

Source/cmInstallCommand.cxx

@@ -645,7 +645,8 @@ bool cmInstallCommand::HandleTargetsMode(std::vector<std::string> const& args)
     // generators for them.
     bool createInstallGeneratorsForTargetFileSets = true;
 
-    if(target.IsFrameworkOnApple())
+    if(target.IsFrameworkOnApple()
+        || target.GetType() == cmTarget::INTERFACE_LIBRARY)
       {
       createInstallGeneratorsForTargetFileSets = false;
       }

Source/cmLocalGenerator.cxx

@@ -541,6 +541,10 @@ void cmLocalGenerator::GenerateTargetManifest()
       t != targets.end(); ++t)
     {
     cmGeneratorTarget& target = *t->second;
+    if (target.Target->GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
     if(configNames.empty())
       {
       target.GenerateTargetManifest(0);
@@ -2829,6 +2833,11 @@ cmLocalGenerator
   cmTargets& tgts = this->Makefile->GetTargets();
   for(cmTargets::iterator l = tgts.begin(); l != tgts.end(); ++l)
     {
+    if (l->second.GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
+
     // Include the user-specified pre-install script for this target.
     if(const char* preinstall = l->second.GetProperty("PRE_INSTALL_SCRIPT"))
       {

Source/cmLocalNinjaGenerator.cxx

@@ -68,7 +68,8 @@ void cmLocalNinjaGenerator::Generate()
   for(cmGeneratorTargetsType::iterator t = targets.begin();
       t != targets.end(); ++t)
     {
-    if (t->second->Target->IsImported())
+    if (t->second->Target->GetType() == cmTarget::INTERFACE_LIBRARY
+        || t->second->Target->IsImported())
       {
       continue;
       }

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -151,7 +151,8 @@ void cmLocalUnixMakefileGenerator3::Generate()
   for(cmGeneratorTargetsType::iterator t = targets.begin();
       t != targets.end(); ++t)
     {
-    if (t->second->Target->IsImported())
+    if (t->second->Target->GetType() == cmTarget::INTERFACE_LIBRARY
+        || t->second->Target->IsImported())
       {
       continue;
       }

Source/cmMakefile.cxx

@@ -868,6 +868,10 @@ void cmMakefile::ConfigureFinalPass()
   for (cmTargets::iterator l = this->Targets.begin();
        l != this->Targets.end(); l++)
     {
+    if (l->second.GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
     l->second.FinishConfigure();
     }
 }
@@ -2256,6 +2260,10 @@ void cmMakefile::ExpandVariablesCMP0019()
        l != this->Targets.end(); ++l)
     {
     cmTarget &t = l->second;
+    if (t.GetType() == cmTarget::INTERFACE_LIBRARY)
+      {
+      continue;
+      }
     includeDirs = t.GetProperty("INCLUDE_DIRECTORIES");
     if(mightExpandVariablesCMP0019(includeDirs))
       {

Source/cmMakefileLibraryTargetGenerator.cxx

@@ -25,9 +25,12 @@ cmMakefileLibraryTargetGenerator
   cmMakefileTargetGenerator(target->Target)
 {
   this->CustomCommandDriver = OnDepends;
+  if (this->Target->GetType() != cmTarget::INTERFACE_LIBRARY)
+    {
     this->Target->GetLibraryNames(
       this->TargetNameOut, this->TargetNameSO, this->TargetNameReal,
       this->TargetNameImport, this->TargetNamePDB, this->ConfigName);
+    }
 
   this->OSXBundleGenerator = new cmOSXBundleGenerator(target,
                                                       this->ConfigName);

Source/cmTarget.cxx

@@ -255,6 +255,8 @@ void cmTarget::SetMakefile(cmMakefile* mf)
   this->IsApple = this->Makefile->IsOn("APPLE");
 
   // Setup default property values.
+  if (this->GetType() != INTERFACE_LIBRARY)
+    {
     this->SetPropertyDefault("INSTALL_NAME_DIR", 0);
     this->SetPropertyDefault("INSTALL_RPATH", "");
     this->SetPropertyDefault("INSTALL_RPATH_USE_LINK_PATH", "OFF");
@@ -280,7 +282,7 @@ void cmTarget::SetMakefile(cmMakefile* mf)
     this->SetPropertyDefault("MACOSX_BUNDLE", 0);
     this->SetPropertyDefault("MACOSX_RPATH", 0);
     this->SetPropertyDefault("NO_SYSTEM_FROM_IMPORTED", 0);
-
+    }
 
   // Collect the set of configuration types.
   std::vector<std::string> configNames;
@@ -300,6 +302,11 @@ void cmTarget::SetMakefile(cmMakefile* mf)
     std::string configUpper = cmSystemTools::UpperCase(*ci);
     for(const char** p = configProps; *p; ++p)
       {
+      if (this->TargetTypeValue == INTERFACE_LIBRARY
+          && strcmp(*p, "MAP_IMPORTED_CONFIG_") != 0)
+        {
+        continue;
+        }
       std::string property = *p;
       property += configUpper;
       this->SetPropertyDefault(property.c_str(), 0);
@@ -311,7 +318,8 @@ void cmTarget::SetMakefile(cmMakefile* mf)
     // did not support this variable.  Projects may still specify the
     // property directly.  TODO: Make this depend on backwards
     // compatibility setting.
-    if(this->TargetTypeValue != cmTarget::EXECUTABLE)
+    if(this->TargetTypeValue != cmTarget::EXECUTABLE
+        && this->TargetTypeValue != cmTarget::INTERFACE_LIBRARY)
       {
       std::string property = cmSystemTools::UpperCase(*ci);
       property += "_POSTFIX";
@@ -352,16 +360,22 @@ void cmTarget::SetMakefile(cmMakefile* mf)
     this->InsertCompileOption(*it);
     }
 
+  if (this->GetType() != INTERFACE_LIBRARY)
+    {
     this->SetPropertyDefault("C_VISIBILITY_PRESET", 0);
     this->SetPropertyDefault("CXX_VISIBILITY_PRESET", 0);
     this->SetPropertyDefault("VISIBILITY_INLINES_HIDDEN", 0);
+    }
 
   if(this->TargetTypeValue == cmTarget::SHARED_LIBRARY
       || this->TargetTypeValue == cmTarget::MODULE_LIBRARY)
     {
     this->SetProperty("POSITION_INDEPENDENT_CODE", "True");
     }
+  if (this->GetType() != INTERFACE_LIBRARY)
+    {
     this->SetPropertyDefault("POSITION_INDEPENDENT_CODE", 0);
+    }
 
   // Record current policies for later use.
 #define CAPTURE_TARGET_POLICY(POLICY) \
@@ -4433,7 +4447,8 @@ bool isLinkDependentProperty(cmTarget const* tgt, const std::string &p,
 bool cmTarget::IsLinkInterfaceDependentBoolProperty(const std::string &p,
                                            const char *config) const
 {
-  if (this->TargetTypeValue == OBJECT_LIBRARY)
+  if (this->TargetTypeValue == OBJECT_LIBRARY
+      || this->TargetTypeValue == INTERFACE_LIBRARY)
     {
     return false;
     }
@@ -4446,7 +4461,8 @@ bool cmTarget::IsLinkInterfaceDependentBoolProperty(const std::string &p,
 bool cmTarget::IsLinkInterfaceDependentStringProperty(const std::string &p,
                                     const char *config) const
 {
-  if (this->TargetTypeValue == OBJECT_LIBRARY)
+  if (this->TargetTypeValue == OBJECT_LIBRARY
+      || this->TargetTypeValue == INTERFACE_LIBRARY)
     {
     return false;
     }
@@ -4458,7 +4474,8 @@ bool cmTarget::IsLinkInterfaceDependentStringProperty(const std::string &p,
 bool cmTarget::IsLinkInterfaceDependentNumberMinProperty(const std::string &p,
                                     const char *config) const
 {
-  if (this->TargetTypeValue == OBJECT_LIBRARY)
+  if (this->TargetTypeValue == OBJECT_LIBRARY
+      || this->TargetTypeValue == INTERFACE_LIBRARY)
     {
     return false;
     }
@@ -4470,7 +4487,8 @@ bool cmTarget::IsLinkInterfaceDependentNumberMinProperty(const std::string &p,
 bool cmTarget::IsLinkInterfaceDependentNumberMaxProperty(const std::string &p,
                                     const char *config) const
 {
-  if (this->TargetTypeValue == OBJECT_LIBRARY)
+  if (this->TargetTypeValue == OBJECT_LIBRARY
+      || this->TargetTypeValue == INTERFACE_LIBRARY)
     {
     return false;
     }
@@ -5105,6 +5123,8 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
         {
         emitted.insert(*li);
         }
+      if (this->GetType() != cmTarget::INTERFACE_LIBRARY)
+        {
         LinkImplementation const* impl = this->GetLinkImplementation(config,
                                                                   headTarget);
         for(std::vector<std::string>::const_iterator
@@ -5136,6 +5156,7 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
           }
         }
       }
+    }
   else if (this->PolicyStatusCMP0022 == cmPolicies::WARN
         || this->PolicyStatusCMP0022 == cmPolicies::OLD)
     // If CMP0022 is NEW then the plain tll signature sets the

Source/cmVisualStudio10TargetGenerator.cxx

@@ -184,7 +184,8 @@ void cmVisualStudio10TargetGenerator::WriteString(const char* line,
 void cmVisualStudio10TargetGenerator::Generate()
 {
   // do not generate external ms projects
-  if(this->Target->GetProperty("EXTERNAL_MSPROJECT"))
+  if(this->Target->GetType() == cmTarget::INTERFACE_LIBRARY
+      || this->Target->GetProperty("EXTERNAL_MSPROJECT"))
     {
     return;
     }