GError: the final chapter

[Havoc Pennington <hp redhat com>]

Hi,

AFAIK the last remaining issue with GError was whether to make it a
static object. In terms of functionality, this is almost a total
toss-up. I like the dynamic object slightly more:
 - it is more "glib-style"
 - it's slightly more abstract, you have mildly more 
   implementation freedom
 - it's more intuitive, the CORBA-style static object is a bit
   confusing

(static object in this case doesn't save any work, since you still
have to _init() and _free())

The primary objection to a dynamic object was that g_error_set() and
g_error_clear() operate on a GError** and aren't methods. To address
that I propose changing them to g_set_error() And g_clear_error().

So, I want to commit this. Final version appended.

Havoc

/* gerror.h - Error reporting system
 *
 *  Copyright 2000 Red Hat, Inc.
 *
 * The Gnome Library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * The Gnome Library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with the Gnome Library; see the file COPYING.LIB.  If not,
 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 *   Boston, MA 02111-1307, USA.
 */

#ifndef __GERROR_H__
#define __GERROR_H__

#ifdef __cplusplus
extern "C"
{
#endif

typedef struct _GError GError;

struct _GError
{
  GQuark       domain;
  gint         code;
  const gchar *message;
};

GError*  g_error_new           (GQuark         domain,
                                gint           code,
                                const gchar   *format,
                                ...) G_GNUC_PRINTF (3, 4);

GError*  g_error_new_literal   (GQuark         domain,
                                gint           code,
                                const gchar   *message);

void     g_error_free          (GError        *error);
GError*  g_error_copy          (const GError  *error);

gboolean g_error_matches       (const GError  *error,
                                GQuark         domain,
                                gint           code);

/* if (err) *err = g_error_new(domain, code, format, ...), also has
 * some sanity checks.
 */
void     g_set_error           (GError       **err,
                                GQuark         domain,
                                gint           code,
                                const gchar   *format,
                                ...) G_GNUC_PRINTF (4, 5);

/* if (err && *err) { g_error_free(*err); *err = NULL; } */
void     g_clear_error         (GError       **err);


#ifdef __cplusplus
}
#endif

#endif /* __GERROR_H__ */


/* GLIB - Library of useful routines for C programming
 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
 * Modified by the GLib Team and others 1997-1999.  See the AUTHORS
 * file for a list of people on the GLib Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GLib at ftp://ftp.gtk.org/pub/gtk/. 
 */

#include "glib.h"

static GError* 
g_error_new_valist(GQuark         domain,
                   gint           code,
                   const gchar   *format,
                   va_list        args)
{
  GError *error;
  
  error = g_new (GError, 1);
  
  error->domain = domain;
  error->code = code;
  error->message = g_strdup_vprintf (format, args);
  
  return error;
}

GError*
g_error_new (GQuark       domain,
             gint         code,
             const gchar *format,
             ...)
{
  GError* error;
  va_list args;

  g_return_val_if_fail (format != NULL, NULL);
  g_return_val_if_fail (domain != 0, NULL);

  va_start (args, format);
  error = g_error_new_valist (domain, code, format, args);
  va_end (args);

  return error;
}

GError*
g_error_new_literal (GQuark         domain,
                     gint           code,
                     const gchar   *message)
{
  GError* err;

  g_return_val_if_fail (message != NULL, NULL);
  g_return_val_if_fail (domain != 0, NULL);

  err = g_new (GError, 1);

  err->domain = domain;
  err->code = code;
  err->message = g_strdup (message);
  
  return err;
}

void
g_error_free (GError *error)
{
  g_return_if_fail (error != NULL);  

  g_free ((gchar*)error->message);

  g_free (error);
}

GError*
g_error_copy (const GError *error)
{
  GError *copy;
  
  g_return_val_if_fail (error != NULL, NULL);

  copy = g_new (GError, 1);

  *copy = *error;

  copy->message = g_strdup (error->message);

  return copy;
}

gboolean
g_error_matches (const GError *error,
                 GQuark        domain,
                 gint          code)
{
  return error &&
    error->domain == domain &&
    error->code == code;
}

void
g_set_error (GError     **err,
             GQuark       domain,
             gint         code,
             const gchar *format,
             ...)
{
  va_list args;

  if (err == NULL)
    return;

  if (*err != NULL)
    g_warning ("GError set over the top of a previous GError or uninitialized memory.\n"
               "This indicates a bug in someone's code. You must ensure an error is NULL before it's set.");
  
  va_start (args, format);
  *err = g_error_new_valist (domain, code, format, args);
  va_end (args);
}

void
g_clear_error (GError **err)
{
  if (err && *err)
    {
      g_error_free (*err);
      *err = NULL;
    }
}