[Libguestfs] [PATCH 4/5] daemon error handling: Define a new function reply_with_perror_errno.

[Richard W.M. Jones]

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 80 OCaml packages (the OPEN alternative to F#)
http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora
-------------- next part --------------
>From 1c3e962a33c89750cd1f251e8e85222e9cd49f3f Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at redhat.com>
Date: Mon, 30 Nov 2009 14:11:20 +0000
Subject: [PATCH 4/5] daemon error handling: Define a new function reply_with_perror_errno.

This allows you to save the errno from a previous call and
pass it to reply_with_perror.

For example, original code:

  err = errno;
  r = some_system_call ();
  do_cleanup ();
  errno = err;
  if (r == -1) {
    reply_with_perror ("failed");
    return -1;
  }

can in future be changed to:

  err = errno;
  r = some_system_call ();
  do_cleanup ();
  if (r == -1) {
    reply_with_perror_errno (err, "failed");
    return -1;
  }
---
 daemon/daemon.h |    7 ++++---
 daemon/proto.c  |    3 +--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/daemon/daemon.h b/daemon/daemon.h
index 6ce46b9..88d0306 100644
--- a/daemon/daemon.h
+++ b/daemon/daemon.h
@@ -119,8 +119,9 @@ extern void main_loop (int sock) __attribute__((noreturn));
 /* ordinary daemon functions use these to indicate errors */
 extern void reply_with_error (const char *fs, ...)
   __attribute__((format (printf,1,2)));
-extern void reply_with_perror (const char *fs, ...)
-  __attribute__((format (printf,1,2)));
+extern void reply_with_perror_errno (int err, const char *fs, ...)
+  __attribute__((format (printf,2,3)));
+#define reply_with_perror(...) reply_with_perror_errno(errno, __VA_ARGS__)
 
 /* daemon functions that receive files (FileIn) should call
  * receive_file for each FileIn parameter.
@@ -130,7 +131,7 @@ extern int receive_file (receive_cb cb, void *opaque);
 
 /* daemon functions that receive files (FileIn) can call this
  * to cancel incoming transfers (eg. if there is a local error),
- * but they MUST then call reply_with_error or reply_with_perror.
+ * but they MUST then call reply_with_*.
  */
 extern void cancel_receive (void);
 
diff --git a/daemon/proto.c b/daemon/proto.c
index e3ff9e9..1ad9d11 100644
--- a/daemon/proto.c
+++ b/daemon/proto.c
@@ -195,12 +195,11 @@ reply_with_error (const char *fs, ...)
 }
 
 void
-reply_with_perror (const char *fs, ...)
+reply_with_perror_errno (int err, const char *fs, ...)
 {
   char buf1[GUESTFS_ERROR_LEN];
   char buf2[GUESTFS_ERROR_LEN];
   va_list args;
-  int err = errno;
 
   va_start (args, fs);
   vsnprintf (buf1, sizeof buf1, fs, args);
-- 
1.6.5.2