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.

19 files changed, 125 insertions, 0 deletions

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)