Process the INTERFACE_PIC property from linked dependencies

This allows a dependee to inform a target that it should have its
POSITION_INDEPENDENT_CODE property set to ON, or OFF. The value of
the POSITION_INDEPENDENT_CODE property, if set, must be consistent
with any INTERFACE_POSITION_INDEPENDENT_CODE properties on dependees.

Add a test covering the consistency checks on platforms where they run.

Source/cmGlobalXCodeGenerator.cxx

@@ -1639,14 +1639,16 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
     if(strcmp(lang, "CXX") == 0)
       {
       this->CurrentLocalGenerator->AddLanguageFlags(cflags, "C", configName);
-      this->CurrentLocalGenerator->AddCMP0018Flags(cflags, &target, "C");
+      this->CurrentLocalGenerator->AddCMP0018Flags(cflags, &target,
+                                                   "C", configName);
       }
 
     // Add language-specific flags.
     this->CurrentLocalGenerator->AddLanguageFlags(flags, lang, configName);
 
     // Add shared-library flags if needed.
-    this->CurrentLocalGenerator->AddCMP0018Flags(flags, &target, lang);
+    this->CurrentLocalGenerator->AddCMP0018Flags(flags, &target,
+                                                 lang, configName);
     }
   else if(binary)
   {

Source/cmLocalGenerator.cxx

@@ -1984,7 +1984,8 @@ void cmLocalGenerator::AddSharedFlags(std::string& flags,
 
 //----------------------------------------------------------------------------
 void cmLocalGenerator::AddCMP0018Flags(std::string &flags, cmTarget* target,
-                                       std::string const& lang)
+                                       std::string const& lang,
+                                       const char *config)
 {
   int targetType = target->GetType();
 
@@ -1997,8 +1998,18 @@ void cmLocalGenerator::AddCMP0018Flags(std::string &flags, cmTarget* target,
     }
   else
     {
-    // Add position independendent flags, if needed.
-    if (target->GetPropertyAsBool("POSITION_INDEPENDENT_CODE"))
+    if (target->GetType() == cmTarget::OBJECT_LIBRARY)
+    {
+      if (target->GetPropertyAsBool("POSITION_INDEPENDENT_CODE"))
+        {
+        this->AddPositionIndependentFlags(flags, lang, targetType);
+        }
+      return;
+    }
+
+    if (target->GetLinkInterfaceDependentBoolProperty(
+                                                "POSITION_INDEPENDENT_CODE",
+                                                config))
       {
       this->AddPositionIndependentFlags(flags, lang, targetType);
       }

Source/cmLocalGenerator.h

@@ -142,7 +142,7 @@ public:
   void AddLanguageFlags(std::string& flags, const char* lang,
                         const char* config);
   void AddCMP0018Flags(std::string &flags, cmTarget* target,
-                       std::string const& lang);
+                       std::string const& lang, const char *config);
   void AddConfigVariableFlags(std::string& flags, const char* var,
                               const char* config);
   ///! Append flags to a string.

Source/cmMakefileTargetGenerator.cxx

@@ -268,7 +268,8 @@ std::string cmMakefileTargetGenerator::GetFlags(const std::string &l)
       this->AddFortranFlags(flags);
       }
 
-    this->LocalGenerator->AddCMP0018Flags(flags, this->Target, lang);
+    this->LocalGenerator->AddCMP0018Flags(flags, this->Target,
+                                          lang, this->ConfigName);
 
     // Add include directory flags.
     this->AddIncludeFlags(flags, lang);

Source/cmNinjaTargetGenerator.cxx

@@ -147,7 +147,8 @@ cmNinjaTargetGenerator::ComputeFlagsForObject(cmSourceFile *source,
 
   // Add shared-library flags if needed.
   this->LocalGenerator->AddCMP0018Flags(flags, this->Target,
-                                        language.c_str());
+                                        language.c_str(),
+                                        this->GetConfigName());
 
   // Add include directory flags.
   {

Source/cmTarget.cxx

@@ -877,6 +877,20 @@ void cmTarget::DefineProperties(cmake *cm)
      "CMAKE_POSITION_INDEPENDENT_CODE if it is set when a target is "
      "created.");
 
+  cm->DefineProperty
+    ("INTERFACE_POSITION_INDEPENDENT_CODE", cmProperty::TARGET,
+     "Whether consumers need to create a position-independent target",
+     "The INTERFACE_POSITION_INDEPENDENT_CODE property informs consumers of "
+     "this target whether they must set their POSITION_INDEPENDENT_CODE "
+     "property to ON.  If this property is set to ON, then the "
+     "POSITION_INDEPENDENT_CODE property on all consumers will be set to "
+     "ON.  Similarly, if this property is set to OFF, then the "
+     "POSITION_INDEPENDENT_CODE property on all consumers will be set to "
+     "OFF.  If this property is undefined, then consumers will determine "
+     "their POSITION_INDEPENDENT_CODE property by other means.  Consumers "
+     "must ensure that the targets that they link to have a consistent "
+     "requirement for their INTERFACE_POSITION_INDEPENDENT_CODE property.");
+
   cm->DefineProperty
     ("POST_INSTALL_SCRIPT", cmProperty::TARGET,
      "Deprecated install support.",

Tests/RunCMake/CMakeLists.txt

@@ -50,6 +50,9 @@ add_RunCMake_test(GeneratorExpression)
 add_RunCMake_test(TargetPropertyGeneratorExpressions)
 add_RunCMake_test(Languages)
 add_RunCMake_test(ObjectLibrary)
+if(NOT WIN32)
+  add_RunCMake_test(PositionIndependentCode)
+endif()
 
 add_RunCMake_test(build_command)
 add_RunCMake_test(find_package)

Tests/RunCMake/PositionIndependentCode/CMakeLists.txt

@@ -0,0 +1,8 @@
+
+cmake_minimum_required(VERSION 2.8)
+project(${RunCMake_TEST} CXX)
+
+# MSVC creates extra targets which pollute the stderr unless we set this.
+set(CMAKE_SUPPRESS_REGENERATION TRUE)
+
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/PositionIndependentCode/Conflict1-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/PositionIndependentCode/Conflict1-stderr.txt

@@ -0,0 +1,3 @@
+CMake Error: Property POSITION_INDEPENDENT_CODE on target "conflict" does
+not match the INTERFACE_POSITION_INDEPENDENT_CODE property requirement
+of dependency "piciface".

Tests/RunCMake/PositionIndependentCode/Conflict1.cmake

@@ -0,0 +1,7 @@
+
+add_library(piciface UNKNOWN IMPORTED)
+set_property(TARGET piciface PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_executable(conflict "main.cpp")
+set_property(TARGET conflict PROPERTY POSITION_INDEPENDENT_CODE OFF)
+target_link_libraries(conflict piciface)

Tests/RunCMake/PositionIndependentCode/Conflict2-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/PositionIndependentCode/Conflict2-stderr.txt

@@ -0,0 +1,3 @@
+CMake Error: The INTERFACE_POSITION_INDEPENDENT_CODE property of "picoff" does
+not agree with the value of POSITION_INDEPENDENT_CODE already determined
+for "conflict".

Tests/RunCMake/PositionIndependentCode/Conflict2.cmake

@@ -0,0 +1,9 @@
+
+add_library(picon UNKNOWN IMPORTED)
+set_property(TARGET picon PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_library(picoff UNKNOWN IMPORTED)
+set_property(TARGET picoff PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE OFF)
+
+add_executable(conflict "main.cpp")
+target_link_libraries(conflict picon picoff)

Tests/RunCMake/PositionIndependentCode/Conflict3-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/PositionIndependentCode/Conflict3-stderr.txt

@@ -0,0 +1,4 @@
+Property POSITION_INDEPENDENT_CODE on target "conflict" is
+implied to be FALSE because it was used to determine the link libraries
+already. The INTERFACE_POSITION_INDEPENDENT_CODE property on
+dependency "picon" is in conflict.

Tests/RunCMake/PositionIndependentCode/Conflict3.cmake

@@ -0,0 +1,12 @@
+
+add_library(picoff UNKNOWN IMPORTED)
+
+add_library(picon UNKNOWN IMPORTED)
+set_property(TARGET picon PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_executable(conflict "main.cpp")
+target_link_libraries(conflict picon)
+set_property(TARGET conflict APPEND PROPERTY
+  LINK_LIBRARIES
+    $<$<NOT:$<BOOL:$<TARGET_PROPERTY:POSITION_INDEPENDENT_CODE>>>:picoff>
+)

Tests/RunCMake/PositionIndependentCode/RunCMakeTest.cmake

@@ -0,0 +1,5 @@
+include(RunCMake)
+
+run_cmake(Conflict1)
+run_cmake(Conflict2)
+run_cmake(Conflict3)

Tests/RunCMake/PositionIndependentCode/main.cpp

@@ -0,0 +1,5 @@
+
+int main(int,char**)
+{
+  return 0;
+}