Add a variable to specify language-wide system include directories

Create a `CMAKE_<LANG>_STANDARD_INCLUDE_DIRECTORIES` variable to specify
system include directories for for `<LANG>` compiler command lines.
This plays a role for include directories as the existing
`CMAKE_<LANG>_STANDARD_LIBRARIES` variable does for link libraries.

4 files changed, 11 insertions, 0 deletions

diff --git a/Tests/IncludeDirectories/CMakeLists.txt b/Tests/IncludeDirectories/CMakeLists.txt
index 9ee1957..523c4f7 100644
--- a/Tests/IncludeDirectories/CMakeLists.txt
+++ b/Tests/IncludeDirectories/CMakeLists.txt
@@ -63,6 +63,7 @@ else()
     PROPERTIES COMPILE_FLAGS "-ITarProp")
 endif()
 
+add_subdirectory(StandardIncludeDirectories)
 add_subdirectory(TargetIncludeDirectories)
 
 set_property(DIRECTORY PROPERTY INCLUDE_DIRECTORIES "${CMAKE_BINARY_DIR}")
diff --git a/Tests/IncludeDirectories/StandardIncludeDirectories/CMakeLists.txt b/Tests/IncludeDirectories/StandardIncludeDirectories/CMakeLists.txt
new file mode 100644
index 0000000..dcbc566
--- /dev/null
+++ b/Tests/IncludeDirectories/StandardIncludeDirectories/CMakeLists.txt
@@ -0,0 +1,5 @@
+# Normally this variable should be set by a platform information module or
+# a toolchain file, but for purposes of this test we simply set it here.
+set(CMAKE_C_STANDARD_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/StdDir)
+
+add_executable(StandardIncludeDirectories main.c)
diff --git a/Tests/IncludeDirectories/StandardIncludeDirectories/StdDir/StdIncDir.h b/Tests/IncludeDirectories/StandardIncludeDirectories/StdDir/StdIncDir.h
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/Tests/IncludeDirectories/StandardIncludeDirectories/StdDir/StdIncDir.h
diff --git a/Tests/IncludeDirectories/StandardIncludeDirectories/main.c b/Tests/IncludeDirectories/StandardIncludeDirectories/main.c
new file mode 100644
index 0000000..edfe9ce
--- /dev/null
+++ b/Tests/IncludeDirectories/StandardIncludeDirectories/main.c
@@ -0,0 +1,5 @@
+#include "StdIncDir.h"
+int main()
+{
+  return 0;
+}