[Guile-commits] GNU Guile branch, master, updated. release_1-9-2-337-g45f15ca

[Ludovic Courtès]

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- Log -----------------------------------------------------------------
commit 45f15cac1f7f36c24ad0734fe128483080272e5f
Author: Ludovic Courtès <address@hidden>
Date:   Fri Sep 11 00:03:03 2009 +0200

    Remove `scm_enter_guile ()' and `scm_leave_guile ()'.
    
    * libguile/threads.c (scm_t_guile_ticket): Remove type.
      (resume, scm_enter_guile, suspend, scm_leave_guile): Remove.
      (scm_i_init_thread_for_guile): Set `t->top' to NULL, which has the
      same effect as calling `scm_enter_guile ()'.
      (scm_leave_guile_cleanup, scm_i_with_guile_and_parent): Remove
      `scm_leave_guile ()' call.

commit 87e003709170c0714ade5cb5a14edeab57558071
Author: Ludovic Courtès <address@hidden>
Date:   Thu Sep 10 23:58:57 2009 +0200

    Add `λ' macro as an alternative to `lambda'.
    
    * module/ice-9/boot-9.scm (λ): New macro.
    
    * NEWS: Update.

commit b7b9328817c0b9d7d4a69c52173ae4ad796be614
Author: Ludovic Courtès <address@hidden>
Date:   Thu Sep 10 19:45:59 2009 +0200

    Report missing libunistring at `configure'-time.
    
    * configure.ac: Reinstate libunistring check from
      1ee2c72eafaae5f91f4c899bc4b4853af5c16f28.

-----------------------------------------------------------------------

Summary of changes:
 NEWS                    |    4 ++
 configure.ac            |    5 ++
 libguile/threads.c      |  135 +----------------------------------------------
 module/ice-9/boot-9.scm |    9 +++-
 4 files changed, 19 insertions(+), 134 deletions(-)

diff --git a/NEWS b/NEWS
index 5785596..ca7ddf6 100644
--- a/NEWS
+++ b/NEWS
@@ -105,6 +105,8 @@ unlikely that any code out there actually used this 
functionality.
 GOOPS, Guile's object system, used to be documented in separate manuals.
 This content is now included in Guile's manual directly.
 
+** Last but not least, the `λ' macro can be used in lieu of `lambda'
+
 ** And of course, the usual collection of bugfixes
  
 Interested users should see the ChangeLog for more information.
@@ -700,6 +702,8 @@ no effect, and will trigger a deprecation warning.
 Instead, use make-typed-array, list->typed-array, or array-type,
 respectively.
 
+** Last but not least, the `λ' macro can be used in lieu of `lambda'
+
 * Changes to the C interface
 
 ** Guile now uses libgc, the Boehm-Demers-Weiser garbage collector
diff --git a/configure.ac b/configure.ac
index f10df10..589c798 100644
--- a/configure.ac
+++ b/configure.ac
@@ -826,6 +826,11 @@ AC_LIB_HAVE_LINKFLAGS(gmp,
   AC_MSG_ERROR([GNU MP 4.1 or greater not found, see README]))
 
 dnl GNU libunistring is checked for by Gnulib's `libunistring' module.
+if test "x$LTLIBUNISTRING" != "x"; then
+  LIBS="$LTLIBUNISTRING $LIBS"
+else
+  AC_MSG_ERROR([GNU libunistring is required, please install it.])
+fi
 
 dnl i18n tests
 #AC_CHECK_HEADERS([libintl.h])
diff --git a/libguile/threads.c b/libguile/threads.c
index 337dd11..3def0f3 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -279,141 +279,12 @@ unblock_from_queue (SCM queue)
   return thread;
 }
 
+
 /* Getting into and out of guile mode.
  */
 
-/* Ken Raeburn observes that the implementation of suspend and resume
-   (and the things that build on top of them) are very likely not
-   correct (see below).  We will need fix this eventually, and that's
-   why scm_leave_guile/scm_enter_guile are not exported in the API.
-
-   Ken writes:
-
-   Consider this sequence:
-
-   Function foo, called in Guile mode, calls suspend (maybe indirectly
-   through scm_leave_guile), which does this:
-
-      // record top of stack for the GC
-      t->top = SCM_STACK_PTR (&t);     // just takes address of automatic
-      var 't'
-      // save registers.
-      SCM_FLUSH_REGISTER_WINDOWS;      // sparc only
-      SCM_I_SETJMP (t->regs);          // here's most of the magic
-
-   ... and returns.
-
-   Function foo has a SCM value X, a handle on a non-immediate object, in
-   a caller-saved register R, and it's the only reference to the object
-   currently.
-
-   The compiler wants to use R in suspend, so it pushes the current
-   value, X, into a stack slot which will be reloaded on exit from
-   suspend; then it loads stuff into R and goes about its business.  The
-   setjmp call saves (some of) the current registers, including R, which
-   no longer contains X.  (This isn't a problem for a normal
-   setjmp/longjmp situation, where longjmp would be called before
-   setjmp's caller returns; the old value for X would be loaded back from
-   the stack after the longjmp, before the function returned.)
-
-   So, suspend returns, loading X back into R (and invalidating the jump
-   buffer) in the process.  The caller foo then goes off and calls a
-   bunch of other functions out of Guile mode, occasionally storing X on
-   the stack again, but, say, much deeper on the stack than suspend's
-   stack frame went, and the stack slot where suspend had written X has
-   long since been overwritten with other values.
-
-   Okay, nothing actively broken so far.  Now, let garbage collection
-   run, triggered by another thread.
-
-   The thread calling foo is out of Guile mode at the time, so the
-   garbage collector just scans a range of stack addresses.  Too bad that
-   X isn't stored there.  So the pointed-to storage goes onto the free
-   list, and I think you can see where things go from there.
-
-   Is there anything I'm missing that'll prevent this scenario from
-   happening?  I mean, aside from, "well, suspend and scm_leave_guile
-   don't have many local variables, so they probably won't need to save
-   any registers on most systems, so we hope everything will wind up in
-   the jump buffer and we'll just get away with it"?
-
-   (And, going the other direction, if scm_leave_guile and suspend push
-   the stack pointer over onto a new page, and foo doesn't make further
-   function calls and thus the stack pointer no longer includes that
-   page, are we guaranteed that the kernel cannot release the now-unused
-   stack page that contains the top-of-stack pointer we just saved?  I
-   don't know if any OS actually does that.  If it does, we could get
-   faults in garbage collection.)
-
-   I don't think scm_without_guile has to have this problem, as it gets
-   more control over the stack handling -- but it should call setjmp
-   itself.  I'd probably try something like:
-
-      // record top of stack for the GC
-      t->top = SCM_STACK_PTR (&t);
-      // save registers.
-      SCM_FLUSH_REGISTER_WINDOWS;
-      SCM_I_SETJMP (t->regs);
-      res = func(data);
-      scm_enter_guile (t);
-
-   ... though even that's making some assumptions about the stack
-   ordering of local variables versus caller-saved registers.
-
-   For something like scm_leave_guile to work, I don't think it can just
-   rely on invalidated jump buffers.  A valid jump buffer, and a handle
-   on the stack state at the point when the jump buffer was initialized,
-   together, would work fine, but I think then we're talking about macros
-   invoking setjmp in the caller's stack frame, and requiring that the
-   caller of scm_leave_guile also call scm_enter_guile before returning,
-   kind of like pthread_cleanup_push/pop calls that have to be paired up
-   in a function.  (In fact, the pthread ones have to be paired up
-   syntactically, as if they might expand to a compound statement
-   incorporating the user's code, and invoking a compiler's
-   exception-handling primitives.  Which might be something to think
-   about for cases where Guile is used with C++ exceptions or
-   pthread_cancel.)
-*/
-
 scm_i_pthread_key_t scm_i_thread_key;
 
-static void
-resume (scm_i_thread *t)
-{
-  t->top = NULL;
-}
-
-typedef void* scm_t_guile_ticket;
-
-static void
-scm_enter_guile (scm_t_guile_ticket ticket)
-{
-  scm_i_thread *t = (scm_i_thread *)ticket;
-  if (t)
-    {
-      resume (t);
-    }
-}
-
-static scm_i_thread *
-suspend (void)
-{
-  scm_i_thread *t = SCM_I_CURRENT_THREAD;
-
-  /* record top of stack for the GC */
-  t->top = SCM_STACK_PTR (&t);
-  /* save registers. */
-  SCM_FLUSH_REGISTER_WINDOWS;
-  SCM_I_SETJMP (t->regs);
-  return t;
-}
-
-static scm_t_guile_ticket
-scm_leave_guile ()
-{
-  scm_i_thread *t = suspend ();
-  return (scm_t_guile_ticket) t;
-}
 
 static scm_i_pthread_mutex_t thread_admin_mutex = 
SCM_I_PTHREAD_MUTEX_INITIALIZER;
 static scm_i_thread *all_threads = NULL;
@@ -699,7 +570,7 @@ scm_i_init_thread_for_guile (SCM_STACKITEM *base, SCM 
parent)
          t->base = base;
 #endif
 
-      scm_enter_guile ((scm_t_guile_ticket) t);
+      t->top = NULL;
       return 1;
     }
   else
@@ -806,7 +677,6 @@ scm_with_guile (void *(*func)(void *), void *data)
 SCM_UNUSED static void
 scm_leave_guile_cleanup (void *x)
 {
-  scm_leave_guile ();
   on_thread_exit (SCM_I_CURRENT_THREAD);
 }
 
@@ -823,7 +693,6 @@ scm_i_with_guile_and_parent (void *(*func)(void *), void 
*data, SCM parent)
       scm_i_pthread_cleanup_push (scm_leave_guile_cleanup, NULL);
       res = scm_c_with_continuation_barrier (func, data);
       scm_i_pthread_cleanup_pop (0);
-      scm_leave_guile ();
     }
   else
     res = scm_c_with_continuation_barrier (func, data);
diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm
index 21e3506..e6824b9 100644
--- a/module/ice-9/boot-9.scm
+++ b/module/ice-9/boot-9.scm
@@ -1,4 +1,4 @@
-;;; installed-scm-file
+;;; -*- mode: scheme; coding: utf-8; -*-
 
 ;;;; Copyright (C) 
1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008,2009
 ;;;; Free Software Foundation, Inc.
@@ -3034,6 +3034,13 @@ module '(ice-9 q) '(make-q q-length))}."
        (defmacro name args . body)
        (export-syntax name)))))
 
+;; And now for the most important macro.
+(define-syntax λ
+  (syntax-rules ()
+    ((_ formals body ...)
+     (lambda formals body ...))))
+
+
 ;; Export a local variable
 
 ;; This function is called from "modules.c".  If you change it, be


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