Don't install headers of builtins into the global install prefix

builtins/vdt/CMakeLists.txt

@@ -30,12 +30,12 @@ set(VDT_INCLUDE_DIRS ${CMAKE_BINARY_DIR}/ginclude)
 add_library(VDT::VDT SHARED IMPORTED GLOBAL)
 add_dependencies(VDT::VDT BUILTIN_VDT)
 set_target_properties(VDT::VDT PROPERTIES IMPORTED_LOCATION ${VDT_LIBRARIES})
-target_include_directories(VDT::VDT INTERFACE $<BUILD_INTERFACE:${VDT_INCLUDE_DIR}> $<INSTALL_INTERFACE:include/>)
+target_include_directories(VDT::VDT INTERFACE $<BUILD_INTERFACE:${VDT_INCLUDE_DIR}> $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/ROOT/builtins/>)
 
 install(FILES ${VDT_LIBRARIES}
         DESTINATION ${CMAKE_INSTALL_LIBDIR} COMPONENT libraries)
 install(DIRECTORY ${CMAKE_BINARY_DIR}/include/vdt
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT extra-headers)
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/ROOT/builtins/ COMPONENT extra-headers)
 set_property(GLOBAL APPEND PROPERTY ROOT_BUILTIN_TARGETS VDT::VDT)
 
 set(VDT_VERSION ${ROOT_VDT_VERSION} PARENT_SCOPE)

cmake/modules/FindVdt.cmake

@@ -34,7 +34,7 @@
 #
 
 if(NOT VDT_INCLUDE_DIR)
-  find_path(VDT_INCLUDE_DIR NAME vdt/vdtMath.h PATH_SUFFIXES include)
+  find_path(VDT_INCLUDE_DIR NAME vdt/vdtMath.h PATH_SUFFIXES include/ ROOT/builtins/ include/ROOT/builtins/)
 endif()
 
 if(NOT VDT_LIBRARY)

test/PostInstall/CMakeLists.txt

@@ -61,4 +61,10 @@ if(BUILD_TESTING)
       PROPERTIES ENVIRONMENT PYTHONPATH=${ROOT_LIBRARY_DIR}
     )
   endif()
+
+  if(TARGET ROOT::ROOTVecOps)
+    add_executable(RVec testRVec.cxx)
+    target_link_libraries(RVec PUBLIC ROOT::ROOTVecOps)
+    add_test(NAME RVec COMMAND $<TARGET_FILE:RVec>)
+  endif()
 endif()

test/PostInstall/testRVec.cxx

@@ -0,0 +1,34 @@
+/*
+RVec can publicly depend on VDT, so here we ensure that the VDT headers are found correctly.
+*/
+
+#include <ROOT/RVec.hxx>
+
+#include <iostream>
+
+#define CHECK(ARG)                      \
+   if (!(ARG)) {                        \
+      success = false;                  \
+      std::cerr << #ARG << " failed\n"; \
+   }
+
+int main()
+{
+   bool success = true;
+
+   ROOT::RVec<ROOT::RVecD> rv{{1., 2., 3., 4., 5.}, {1., 2., 3., 4., 5.}};
+   auto sum = rv[0] + rv[1];
+   CHECK(sum.size() == rv[0].size())
+   CHECK(sum[3] == 8.)
+
+#ifdef R__HAS_VDT
+   ROOT::RVecD rv2{1., 2., 3., 4., 5.};
+   auto logs = fast_log(rv2);
+   CHECK(std::fabs(logs[0]) < 1.E-15)
+   CHECK(std::fabs(logs[1] - std::log(2.)) < 1.E-15);
+   if (!success)
+      std::cout << "logs=" << logs << "\n";
+#endif
+
+   return success ? 0 : 1;
+}