COMP: Remove inclusion of .hxx files as headers

The ability to include either .h or .hxx files as
header files required recursively reading the
.h files twice.  The added complexity is
unnecessary, costly, and can confuse static
analysis tools that monitor header guardes (due
to reaching the maximum depth of recursion
limits for nested #ifdefs in checking).

Co-authored-by: Simon Rit <simon.rit@creatis.insa-lyon.fr>

CMake/ITKModuleHeaderTest.cmake

@@ -36,8 +36,7 @@ macro( itk_module_headertest _name )
     # effected.
     set( _include ${${_name}_SOURCE_DIR}/include )
     file( GLOB _h_files ${_include}/*.h )
-    file( GLOB _hxx_files ${_include}/*.hxx )
-    set( _header_files ${_h_files} ${_hxx_files} )
+    set( _header_files ${_h_files} )
     list( LENGTH _h_files _num_headers )
     set( _outputs ${${_name}_BINARY_DIR}/test/${_name}HeaderTest1.cxx )
     set( _test_num 1 )

Utilities/Maintenance/BuildHeaderTest.py

@@ -130,15 +130,11 @@ def main():
         else:
             max_idx = added_header_idx + maximum_number_of_headers
         for i in range(added_header_idx, max_idx):
-            # Use the .hxx if possible.
-            hxx_file = h_files[i][:-1] + "hxx"
             # Files that include VTK headers need to link to VTK.
             if h_files[i] in BANNED_HEADERS or h_files[i].lower().find("vtk") != -1:
                 to_include = (
                     '// #include "' + h_files[i] + '" // Banned in BuildHeaderTest.py\n'
                 )
-            elif os.path.exists(os.path.join(module_source_path, "include", hxx_file)):
-                to_include = '#include "' + hxx_file + '"\n'
             else:
                 to_include = '#include "' + h_files[i] + '"\n'