multiple values bug in head / call-with-input-file

[Daniel Llorens]

Hello,

I noticed this:

scheme@(guile-user)> (call-with-input-string "hello" (lambda (p) (values 1 2)))
$1 = 1
$2 = 2

but:

scheme@(guile-user)> (call-with-input-file "hello" (lambda (p) (values 1 2)))
$1 = 1

I look up call-with-input-file and I see:

(define (call-with-input-file str proc)
  (let* ((file (open-input-file str))
         (ans (proc file)))
    (close-input-port file)
    ans))

Now, in Guile 1.8:

guile> (let ((a (values 1 2))) a)
1
2

But in Guile 2.0.1:

scheme@(guile-user)> (let ((a (values 1 2))) a)
$1 = 1

The second one breaks call-with-input-file, but probably both should be errors.

Anyway, here is a patch for call-with-input/output-file that avoids the issue.

Regards,
        
        Daniel



From 06f8aea901cd3da68a409a9932757209d91efc40 Mon Sep 17 00:00:00 2001
From: Daniel Llorens <address@hidden>
Date: Mon, 2 May 2011 14:54:20 +0200
Subject: [PATCH] Fix call-with-input-file, call-with-output-file with multiple 
values

* module/ice-9/r4rs.scm: Write call-with-input-file, call-with-input-file in 
terms of dynamic-wind.
---
 module/ice-9/r4rs.scm |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/module/ice-9/r4rs.scm b/module/ice-9/r4rs.scm
index 4d3feba..337e196 100644
--- a/module/ice-9/r4rs.scm
+++ b/module/ice-9/r4rs.scm
@@ -144,10 +144,11 @@ automatically and the value yielded by the procedure is 
returned.
 If the procedure does not return, then the port will not be closed
 automatically unless it is possible to prove that the port will
 never again be used for a read or write operation."
-  (let* ((file (open-input-file str))
-        (ans (proc file)))
-    (close-input-port file)
-    ans))
+  (let ((port #f))
+    (dynamic-wind
+      (lambda () (set! port (open-input-file str)))
+      (lambda () (proc port))
+      (lambda () (if port (close-input-port port))))))
 
 (define (call-with-output-file str proc)
   "PROC should be a procedure of one argument, and STR should be a
@@ -160,10 +161,11 @@ automatically and the value yielded by the procedure is 
returned.
 If the procedure does not return, then the port will not be closed
 automatically unless it is possible to prove that the port will
 never again be used for a read or write operation."
-  (let* ((file (open-output-file str))
-        (ans (proc file)))
-    (close-output-port file)
-    ans))
+  (let ((port #f))
+    (dynamic-wind
+      (lambda () (set! port (open-output-file str)))
+      (lambda () (proc port))
+      (lambda () (if port (close-output-port port))))))
 
 (define (with-input-from-port port thunk)
   (let* ((swaports (lambda () (set! port (set-current-input-port port)))))
-- 
1.7.1