src/jdk.jextract/share/classes/com/sun/tools/jextract/JavaSourceFactory.java

*** 166,176 ****
      private void addNativeLocation(boolean align, JavaSourceBuilder jsb, SourceLocation src) {
          if (! noNativeLocations) {
              SourceLocation.Location loc = src.getFileLocation();
              Path p = loc.path();
              Map<String, Object> fields = new HashMap<>();
!             fields.put("file", p == null ? "builtin" :  p.toAbsolutePath().toString().replace("\\", "\\\\"));
              fields.put("line", loc.line());
              fields.put("column", loc.column());
              jsb.addAnnotation(align, NATIVE_LOCATION, fields);
          }
      }
--- 166,176 ----
      private void addNativeLocation(boolean align, JavaSourceBuilder jsb, SourceLocation src) {
          if (! noNativeLocations) {
              SourceLocation.Location loc = src.getFileLocation();
              Path p = loc.path();
              Map<String, Object> fields = new HashMap<>();
!             fields.put("file", p == null ? "<builtin>" :  p.toAbsolutePath().toString().replace("\\", "\\\\"));
              fields.put("line", loc.line());
              fields.put("column", loc.column());
              jsb.addAnnotation(align, NATIVE_LOCATION, fields);
          }
      }