Add the INTERFACE_LIBRARY target type.

This target type only contains INTERFACE_* properties, so it can be
used as a structural node. The target-specific commands enforce
that they may only be used with the INTERFACE keyword when used
with INTERFACE_LIBRARY targets. The old-style target properties
matching LINK_INTERFACE_LIBRARIES_<CONFIG> are always ignored for
this target type.

The name of the INTERFACE_LIBRARY must match a validity generator
expression. The validity is similar to that of an ALIAS target,
but with the additional restriction that it may not contain
double colons. Double colons will carry the meaning of IMPORTED
or ALIAS targets in CMake 2.8.13.

An ALIAS target may be created for an INTERFACE library.

At this point it can not be exported and does not appear in the
buildsystem and project files are not created for them. That may
be added as a feature in a later commit.

The generators need some changes to handle the INTERFACE_LIBRARY
targets returned by cmComputeLinkInterface::GetItems. The Ninja
generator does not use that API, so it doesn't require changes
related to that.

32 files changed, 273 insertions, 1 deletions

diff --git a/Tests/AliasTarget/CMakeLists.txt b/Tests/AliasTarget/CMakeLists.txt
index a5eb0f6..fdb1638 100644
--- a/Tests/AliasTarget/CMakeLists.txt
+++ b/Tests/AliasTarget/CMakeLists.txt
@@ -45,3 +45,6 @@ get_property(_alt2 TARGET PREFIX::Foo PROPERTY ALIASED_TARGET)
 if (NOT ${_alt2} STREQUAL foo)
   message(SEND_ERROR "ALIASED_TARGET is not foo.")
 endif()
+
+add_library(iface INTERFACE)
+add_library(Alias::Iface ALIAS iface)
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index 9c3ed59..ca32aac 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -246,6 +246,7 @@ if(BUILD_TESTING)
   ADD_TEST_MACRO(CompileOptions CompileOptions)
   ADD_TEST_MACRO(CompatibleInterface CompatibleInterface)
   ADD_TEST_MACRO(AliasTarget AliasTarget)
+  ADD_TEST_MACRO(InterfaceLibrary InterfaceLibrary)
   set_tests_properties(EmptyLibrary PROPERTIES
     PASS_REGULAR_EXPRESSION "CMake Error: CMake can not determine linker language for target: test")
   ADD_TEST_MACRO(CrossCompile CrossCompile)
diff --git a/Tests/CompatibleInterface/CMakeLists.txt b/Tests/CompatibleInterface/CMakeLists.txt
index ae1d2fa..5ee9fd7 100644
--- a/Tests/CompatibleInterface/CMakeLists.txt
+++ b/Tests/CompatibleInterface/CMakeLists.txt
@@ -6,7 +6,7 @@ project(CompatibleInterface)
 include(GenerateExportHeader)
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
-add_library(iface1 empty.cpp)
+add_library(iface1 INTERFACE)
 set_property(TARGET iface1 APPEND PROPERTY
   COMPATIBLE_INTERFACE_BOOL
     BOOL_PROP1
diff --git a/Tests/InterfaceLibrary/CMakeLists.txt b/Tests/InterfaceLibrary/CMakeLists.txt
new file mode 100644
index 0000000..53aeb03
--- /dev/null
+++ b/Tests/InterfaceLibrary/CMakeLists.txt
@@ -0,0 +1,15 @@
+
+cmake_minimum_required(VERSION 2.8)
+
+project(InterfaceLibrary)
+
+add_library(iface_nodepends INTERFACE)
+target_compile_definitions(iface_nodepends INTERFACE IFACE_DEFINE)
+
+add_executable(InterfaceLibrary definetestexe.cpp)
+target_link_libraries(InterfaceLibrary iface_nodepends)
+
+add_subdirectory(libsdir)
+
+add_executable(sharedlibtestexe sharedlibtestexe.cpp)
+target_link_libraries(sharedlibtestexe shared_iface)
diff --git a/Tests/InterfaceLibrary/definetestexe.cpp b/Tests/InterfaceLibrary/definetestexe.cpp
new file mode 100644
index 0000000..decd37c
--- /dev/null
+++ b/Tests/InterfaceLibrary/definetestexe.cpp
@@ -0,0 +1,9 @@
+
+#ifndef IFACE_DEFINE
+#error Expected IFACE_DEFINE
+#endif
+
+int main(int,char**)
+{
+  return 0;
+}
diff --git a/Tests/InterfaceLibrary/libsdir/CMakeLists.txt b/Tests/InterfaceLibrary/libsdir/CMakeLists.txt
new file mode 100644
index 0000000..6999646
--- /dev/null
+++ b/Tests/InterfaceLibrary/libsdir/CMakeLists.txt
@@ -0,0 +1,26 @@
+
+include(GenerateExportHeader)
+
+add_library(sharedlib SHARED sharedlib.cpp)
+generate_export_header(sharedlib)
+
+add_library(shareddependlib SHARED shareddependlib.cpp)
+generate_export_header(shareddependlib)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+set(CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE ON)
+
+target_link_libraries(sharedlib PUBLIC shareddependlib)
+
+target_include_directories(shareddependlib
+  PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/shareddependlib")
+target_compile_definitions(shareddependlib
+  INTERFACE $<1:SHAREDDEPENDLIB_DEFINE>)
+
+target_include_directories(sharedlib
+  PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/sharedlib")
+target_compile_definitions(shareddependlib
+  INTERFACE $<1:SHAREDLIB_DEFINE>)
+
+add_library(shared_iface INTERFACE)
+target_link_libraries(shared_iface INTERFACE sharedlib)
diff --git a/Tests/InterfaceLibrary/libsdir/shareddependlib.cpp b/Tests/InterfaceLibrary/libsdir/shareddependlib.cpp
new file mode 100644
index 0000000..378ba81
--- /dev/null
+++ b/Tests/InterfaceLibrary/libsdir/shareddependlib.cpp
@@ -0,0 +1,7 @@
+
+#include "shareddependlib.h"
+
+int SharedDependLibObject::foo() const
+{
+  return 0;
+}
diff --git a/Tests/InterfaceLibrary/libsdir/shareddependlib/shareddependlib.h b/Tests/InterfaceLibrary/libsdir/shareddependlib/shareddependlib.h
new file mode 100644
index 0000000..ad9b484
--- /dev/null
+++ b/Tests/InterfaceLibrary/libsdir/shareddependlib/shareddependlib.h
@@ -0,0 +1,12 @@
+
+#ifndef SHAREDDEPENDLIB_H
+#define SHAREDDEPENDLIB_H
+
+#include "shareddependlib_export.h"
+
+struct SHAREDDEPENDLIB_EXPORT SharedDependLibObject
+{
+  int foo() const;
+};
+
+#endif
diff --git a/Tests/InterfaceLibrary/libsdir/sharedlib.cpp b/Tests/InterfaceLibrary/libsdir/sharedlib.cpp
new file mode 100644
index 0000000..c49ce90
--- /dev/null
+++ b/Tests/InterfaceLibrary/libsdir/sharedlib.cpp
@@ -0,0 +1,12 @@
+
+#include "sharedlib.h"
+
+SharedDependLibObject SharedLibObject::object() const
+{
+  SharedDependLibObject sdlo;
+  return sdlo;
+}
+int SharedLibObject::foo() const
+{
+  return 0;
+}
diff --git a/Tests/InterfaceLibrary/libsdir/sharedlib/sharedlib.h b/Tests/InterfaceLibrary/libsdir/sharedlib/sharedlib.h
new file mode 100644
index 0000000..5b3c7db
--- /dev/null
+++ b/Tests/InterfaceLibrary/libsdir/sharedlib/sharedlib.h
@@ -0,0 +1,15 @@
+
+#ifndef SHAREDLIB_H
+#define SHAREDLIB_H
+
+#include "sharedlib_export.h"
+
+#include "shareddependlib.h"
+
+struct SHAREDLIB_EXPORT SharedLibObject
+{
+  SharedDependLibObject object() const;
+  int foo() const;
+};
+
+#endif
diff --git a/Tests/InterfaceLibrary/sharedlibtestexe.cpp b/Tests/InterfaceLibrary/sharedlibtestexe.cpp
new file mode 100644
index 0000000..c677f70
--- /dev/null
+++ b/Tests/InterfaceLibrary/sharedlibtestexe.cpp
@@ -0,0 +1,19 @@
+
+#ifndef SHAREDLIB_DEFINE
+#error Expected SHAREDLIB_DEFINE
+#endif
+
+#ifndef SHAREDDEPENDLIB_DEFINE
+#error Expected SHAREDDEPENDLIB_DEFINE
+#endif
+
+#include "sharedlib.h"
+#include "shareddependlib.h"
+
+int main(int,char**)
+{
+  SharedLibObject sl;
+  SharedDependLibObject sdl = sl.object();
+
+  return sdl.foo() + sl.foo();
+}
diff --git a/Tests/PositionIndependentTargets/CMakeLists.txt b/Tests/PositionIndependentTargets/CMakeLists.txt
index eec893d..e79f3b7 100644
--- a/Tests/PositionIndependentTargets/CMakeLists.txt
+++ b/Tests/PositionIndependentTargets/CMakeLists.txt
@@ -9,5 +9,6 @@ include_directories("${CMAKE_CURRENT_SOURCE_DIR}") # For pic_test.h
 
 add_subdirectory(global)
 add_subdirectory(targets)
+add_subdirectory(interface)
 
 add_executable(PositionIndependentTargets main.cpp)
diff --git a/Tests/PositionIndependentTargets/interface/CMakeLists.txt b/Tests/PositionIndependentTargets/interface/CMakeLists.txt
new file mode 100644
index 0000000..65f3b76
--- /dev/null
+++ b/Tests/PositionIndependentTargets/interface/CMakeLists.txt
@@ -0,0 +1,27 @@
+
+add_library(piciface INTERFACE)
+set_property(TARGET piciface PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_executable(test_empty_iface "${CMAKE_CURRENT_SOURCE_DIR}/../pic_main.cpp")
+target_link_libraries(test_empty_iface piciface)
+
+add_library(sharedlib SHARED "${CMAKE_CURRENT_SOURCE_DIR}/../pic_lib.cpp")
+target_link_libraries(sharedlib piciface)
+set_property(TARGET sharedlib PROPERTY DEFINE_SYMBOL PIC_TEST_BUILD_DLL)
+
+add_executable(test_iface_via_shared "${CMAKE_CURRENT_SOURCE_DIR}/../pic_main.cpp")
+target_link_libraries(test_iface_via_shared sharedlib)
+
+add_library(sharedlibpic SHARED "${CMAKE_CURRENT_SOURCE_DIR}/../pic_lib.cpp")
+set_property(TARGET sharedlibpic PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+set_property(TARGET sharedlibpic PROPERTY DEFINE_SYMBOL PIC_TEST_BUILD_DLL)
+
+add_library(shared_iface INTERFACE)
+target_link_libraries(shared_iface INTERFACE sharedlibpic)
+
+add_executable(test_shared_via_iface "${CMAKE_CURRENT_SOURCE_DIR}/../pic_main.cpp")
+target_link_libraries(test_shared_via_iface shared_iface)
+
+add_executable(test_shared_via_iface_non_conflict "${CMAKE_CURRENT_SOURCE_DIR}/../pic_main.cpp")
+set_property(TARGET test_shared_via_iface_non_conflict PROPERTY POSITION_INDEPENDENT_CODE ON)
+target_link_libraries(test_shared_via_iface_non_conflict shared_iface)
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index e45aba3..5d662d1 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -100,6 +100,7 @@ add_RunCMake_test(variable_watch)
 add_RunCMake_test(CMP0004)
 add_RunCMake_test(TargetPolicies)
 add_RunCMake_test(alias_targets)
+add_RunCMake_test(interface_library)
 
 find_package(Qt4 QUIET)
 find_package(Qt5Core QUIET)
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict4-result.txt b/Tests/RunCMake/PositionIndependentCode/Conflict4-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict4-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict4-stderr.txt b/Tests/RunCMake/PositionIndependentCode/Conflict4-stderr.txt
new file mode 100644
index 0000000..76d5ea0
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict4-stderr.txt
@@ -0,0 +1,4 @@
+CMake Error: 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.
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict4.cmake b/Tests/RunCMake/PositionIndependentCode/Conflict4.cmake
new file mode 100644
index 0000000..ff5dfb3
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict4.cmake
@@ -0,0 +1,8 @@
+
+add_library(piciface INTERFACE)
+
+add_library(picon INTERFACE)
+set_property(TARGET picon PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_executable(conflict "main.cpp")
+target_link_libraries(conflict picon $<$<BOOL:$<TARGET_PROPERTY:POSITION_INDEPENDENT_CODE>>:piciface>)
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict5-result.txt b/Tests/RunCMake/PositionIndependentCode/Conflict5-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict5-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict5-stderr.txt b/Tests/RunCMake/PositionIndependentCode/Conflict5-stderr.txt
new file mode 100644
index 0000000..ecd0492
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict5-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".
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict5.cmake b/Tests/RunCMake/PositionIndependentCode/Conflict5.cmake
new file mode 100644
index 0000000..e6055f4
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict5.cmake
@@ -0,0 +1,9 @@
+
+add_library(picon INTERFACE)
+set_property(TARGET picon PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_library(picoff INTERFACE)
+set_property(TARGET picoff PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE OFF)
+
+add_executable(conflict "main.cpp")
+target_link_libraries(conflict picon picoff)
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict6-result.txt b/Tests/RunCMake/PositionIndependentCode/Conflict6-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict6-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict6-stderr.txt b/Tests/RunCMake/PositionIndependentCode/Conflict6-stderr.txt
new file mode 100644
index 0000000..0254e55
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict6-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.
diff --git a/Tests/RunCMake/PositionIndependentCode/Conflict6.cmake b/Tests/RunCMake/PositionIndependentCode/Conflict6.cmake
new file mode 100644
index 0000000..7ea7c5f
--- /dev/null
+++ b/Tests/RunCMake/PositionIndependentCode/Conflict6.cmake
@@ -0,0 +1,8 @@
+
+add_library(picoff INTERFACE)
+
+add_library(picon INTERFACE)
+set_property(TARGET picon PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
+
+add_executable(conflict "main.cpp")
+target_link_libraries(conflict picon $<$<NOT:$<BOOL:$<TARGET_PROPERTY:POSITION_INDEPENDENT_CODE>>>:picoff>)
diff --git a/Tests/RunCMake/PositionIndependentCode/RunCMakeTest.cmake b/Tests/RunCMake/PositionIndependentCode/RunCMakeTest.cmake
index 64a340c..3a2009b 100644
--- a/Tests/RunCMake/PositionIndependentCode/RunCMakeTest.cmake
+++ b/Tests/RunCMake/PositionIndependentCode/RunCMakeTest.cmake
@@ -3,3 +3,6 @@ include(RunCMake)
 run_cmake(Conflict1)
 run_cmake(Conflict2)
 run_cmake(Conflict3)
+run_cmake(Conflict4)
+run_cmake(Conflict5)
+run_cmake(Conflict6)
diff --git a/Tests/RunCMake/interface_library/CMakeLists.txt b/Tests/RunCMake/interface_library/CMakeLists.txt
new file mode 100644
index 0000000..12cd3c7
--- /dev/null
+++ b/Tests/RunCMake/interface_library/CMakeLists.txt
@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 2.8.4)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/interface_library/RunCMakeTest.cmake b/Tests/RunCMake/interface_library/RunCMakeTest.cmake
new file mode 100644
index 0000000..56caf68
--- /dev/null
+++ b/Tests/RunCMake/interface_library/RunCMakeTest.cmake
@@ -0,0 +1,4 @@
+include(RunCMake)
+
+run_cmake(invalid_name)
+run_cmake(target_commands)
diff --git a/Tests/RunCMake/interface_library/invalid_name-result.txt b/Tests/RunCMake/interface_library/invalid_name-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/interface_library/invalid_name-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/interface_library/invalid_name-stderr.txt b/Tests/RunCMake/interface_library/invalid_name-stderr.txt
new file mode 100644
index 0000000..c66e080
--- /dev/null
+++ b/Tests/RunCMake/interface_library/invalid_name-stderr.txt
@@ -0,0 +1,9 @@
+CMake Error at invalid_name.cmake:2 \(add_library\):
+  add_library Invalid name for INTERFACE library target: if\$ace
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at invalid_name.cmake:4 \(add_library\):
+  add_library Invalid name for INTERFACE library target: iface::target
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/interface_library/invalid_name.cmake b/Tests/RunCMake/interface_library/invalid_name.cmake
new file mode 100644
index 0000000..51a109d
--- /dev/null
+++ b/Tests/RunCMake/interface_library/invalid_name.cmake
@@ -0,0 +1,4 @@
+
+add_library(if$ace INTERFACE)
+
+add_library(iface::target INTERFACE)
diff --git a/Tests/RunCMake/interface_library/target_commands-result.txt b/Tests/RunCMake/interface_library/target_commands-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/interface_library/target_commands-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/interface_library/target_commands-stderr.txt b/Tests/RunCMake/interface_library/target_commands-stderr.txt
new file mode 100644
index 0000000..be11b77
--- /dev/null
+++ b/Tests/RunCMake/interface_library/target_commands-stderr.txt
@@ -0,0 +1,47 @@
+CMake Error at target_commands.cmake:4 \(target_link_libraries\):
+  INTERFACE library can only be used with the INTERFACE keyword of
+  target_link_libraries
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:5 \(target_link_libraries\):
+  INTERFACE library can only be used with the INTERFACE keyword of
+  target_link_libraries
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:6 \(target_link_libraries\):
+  INTERFACE library can only be used with the INTERFACE keyword of
+  target_link_libraries
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:7 \(target_link_libraries\):
+  INTERFACE library can only be used with the INTERFACE keyword of
+  target_link_libraries
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:9 \(target_include_directories\):
+  target_include_directories may only be set INTERFACE properties on
+  INTERFACE targets
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:10 \(target_include_directories\):
+  target_include_directories may only be set INTERFACE properties on
+  INTERFACE targets
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:12 \(target_compile_definitions\):
+  target_compile_definitions may only be set INTERFACE properties on
+  INTERFACE targets
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at target_commands.cmake:13 \(target_compile_definitions\):
+  target_compile_definitions may only be set INTERFACE properties on
+  INTERFACE targets
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/interface_library/target_commands.cmake b/Tests/RunCMake/interface_library/target_commands.cmake
new file mode 100644
index 0000000..3182e89
--- /dev/null
+++ b/Tests/RunCMake/interface_library/target_commands.cmake
@@ -0,0 +1,13 @@
+
+add_library(iface INTERFACE)
+
+target_link_libraries(iface PRIVATE foo)
+target_link_libraries(iface PUBLIC foo)
+target_link_libraries(iface foo)
+target_link_libraries(iface LINK_INTERFACE_LIBRARIES foo)
+
+target_include_directories(iface PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}")
+target_include_directories(iface PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
+
+target_compile_definitions(iface PRIVATE SOME_DEFINE)
+target_compile_definitions(iface PUBLIC SOME_DEFINE)