fix relative-path handling for source locations in bytecode

Closes PR 15174

pkgs/racket-test-core/tests/racket/stx.rktl

@@ -2204,6 +2204,29 @@
                  name)])))
   (eval '(m racket/base values)))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check marshaling and unmarshaling with relative paths
+
+(let ()
+  (define dir (find-system-path 'temp-dir))
+
+  (define x (parameterize ([current-namespace (make-base-namespace)])
+              (compile (datum->syntax #f '#'x (vector (build-path dir "sub" "x.rkt")
+                                                      1
+                                                      1
+                                                      1
+                                                      1)))))
+  (define-values (i o) (make-pipe))
+  (parameterize ([current-write-relative-directory
+                  (cons (build-path dir "nested")
+                        dir)])
+    (write x o))
+  (test (build-path dir "inner" 'up "sub" "x.rkt")
+        syntax-source
+        (eval (parameterize ([read-accept-compiled #t]
+                             [current-load-relative-directory (build-path dir "inner")])
+                (read i)))))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/racket/src/file.c

@@ -5693,7 +5693,7 @@ Scheme_Object *scheme_extract_relative_to(Scheme_Object *obj, Scheme_Object *dir
 
     while (!SCHEME_NULLP(be)) {
       if (cache) {
-        obj = scheme_make_pair(up_symbol, scheme_null);
+        obj = scheme_make_pair(up_symbol, obj);
       } else {
         a[0] = up_symbol;
         a[1] = obj;