cs: fix truncation of path information in optimization info

Handle not-this-platform paths that manage to evade the heuristics for
converting paths to and from relative form. Otherwise, building can go
wrong on on Windows when using machine-independent starting files
generated on Unix-like systems.

racket/collects/racket/private/truncate-path.rkt

@@ -1,30 +1,37 @@
 #lang racket/base
 (provide truncate-path)
 
-;; Drop information from the path `p` in the same way as marshaling a
-;; path in a srcloc as part of compiled code
+;; Drop information from the path-for-some-system `p` in the same way
+;; as marshaling a path in a srcloc as part of compiled code
 (define (truncate-path p)
   (define-values (base1 name1 dir?) (split-path p))
   (cond
-    [(path? base1)
+    [(path-for-some-system? base1)
      (define-values (base2 name2 dir?) (split-path base1))
      (cond
        [(not base2)
         ;; Path at a root
-        (path->string p)]
+        (path-for-some-system->string p)]
        [(symbol? name2)
         ;; "." or ".." before a name
         (string-append ".../" (path-elem->string name1))]
        [else
-        (string-append ".../" (path->string name2) "/" (path-elem->string name1))])]
+        (string-append ".../" (path-for-some-system->string name2) "/" (path-elem->string name1))])]
     [(eq? base1 'relative)
      (path-elem->string name1)]
     [else
      ;; Path is a root, ".", or ".."
-     (path->string p)]))
+     (path-for-some-system->string p)]))
 
 (define (path-elem->string p)
   (cond
     [(eq? p 'same) "."]
     [(eq? p 'up) ".."]
-    [else (path->string p)]))
+    [else (path-for-some-system->string p)]))
+
+(define (path-for-some-system->string p)
+  (cond
+    [(path? p) (path->string p)]
+    [else
+     ;; There's no right answer here, but UTF-8 likely works out
+     (bytes->string/utf-8 (path->bytes p) #\uFFFD)]))

racket/src/schemify/wrap-path.rkt

@@ -15,11 +15,13 @@
      (define u-e (wrap-truncate-paths orig))
      (define-values (src line col pos span) (wrap-source e))
      (cond
-       [(and (not (path? src))
+       [(and (not (path-for-some-system? src))
              (eq? orig u-e))
         e]
+       [(path-for-some-system? src)
+        (reannotate/new-srcloc e u-e (srcloc (truncate-path src) line col pos span))]
        [else
-        (reannotate/new-srcloc e u-e (srcloc (truncate-path src) line col pos span))])]
+        (reannotate e u-e)])]
     [(pair? e)
      (define a (wrap-truncate-paths (car e)))
      (define d (wrap-truncate-paths (cdr e)))