/* 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 Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  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/.

 */

/**

 * SECTION:error_reporting

 * @Title: Error Reporting

 * @Short_description: a system for reporting errors

 *

 * GLib provides a standard method of reporting errors from a called

 * function to the calling code. (This is the same problem solved by

 * exceptions in other languages.) It's important to understand that

 * this method is both a data type (the #GError struct) and a [set of

 * rules][gerror-rules]. If you use #GError incorrectly, then your code will not

 * properly interoperate with other code that uses #GError, and users

 * of your API will probably get confused. In most cases, [using #GError is

 * preferred over numeric error codes][gerror-comparison], but there are

 * situations where numeric error codes are useful for performance.

 *

 * First and foremost: #GError should only be used to report recoverable

 * runtime errors, never to report programming errors. If the programmer

 * has screwed up, then you should use g_warning(), g_return_if_fail(),

 * g_assert(), g_error(), or some similar facility. (Incidentally,

 * remember that the g_error() function should only be used for

 * programming errors, it should not be used to print any error

 * reportable via #GError.)

 *

 * Examples of recoverable runtime errors are "file not found" or

 * "failed to parse input." Examples of programming errors are "NULL

 * passed to strcmp()" or "attempted to free the same pointer twice."

 * These two kinds of errors are fundamentally different: runtime errors

 * should be handled or reported to the user, programming errors should

 * be eliminated by fixing the bug in the program. This is why most

 * functions in GLib and GTK+ do not use the #GError facility.

 *

 * Functions that can fail take a return location for a #GError as their

 * last argument. On error, a new #GError instance will be allocated and

 * returned to the caller via this argument. For example:

 * |[

 * gboolean g_file_get_contents (const gchar  *filename,

 *                               gchar       **contents,

 *                               gsize        *length,

 *                               GError      **error);

 * ]|

 * If you pass a non-%NULL value for the `error` argument, it should

 * point to a location where an error can be placed. For example:

 * |[

 * gchar *contents;

 * GError *err = NULL;

 *

 * g_file_get_contents ("foo.txt", &contents, NULL, &err;;

 * g_assert ((contents == NULL && err != NULL) || (contents != NULL && err == NULL));

 * if (err != NULL)

 *   {

 *     // Report error to user, and free error

 *     g_assert (contents == NULL);

 *     fprintf (stderr, "Unable to read file: %s\n", err->message);

 *     g_error_free (err);

 *   }

 * else

 *   {

 *     // Use file contents

 *     g_assert (contents != NULL);

 *   }

 * ]|

 * Note that `err != NULL` in this example is a reliable indicator

 * of whether g_file_get_contents() failed. Additionally,

 * g_file_get_contents() returns a boolean which

 * indicates whether it was successful.

 *

 * Because g_file_get_contents() returns %FALSE on failure, if you

 * are only interested in whether it failed and don't need to display

 * an error message, you can pass %NULL for the @error argument:

 * |[

 * if (g_file_get_contents ("foo.txt", &contents, NULL, NULL)) // ignore errors

 *   // no error occurred 

 *   ;

 * else

 *   // error

 *   ;

 * ]|

 *

 * The #GError object contains three fields: @domain indicates the module

 * the error-reporting function is located in, @code indicates the specific

 * error that occurred, and @message is a user-readable error message with

 * as many details as possible. Several functions are provided to deal

 * with an error received from a called function: g_error_matches()

 * returns %TRUE if the error matches a given domain and code,

 * g_propagate_error() copies an error into an error location (so the

 * calling function will receive it), and g_clear_error() clears an

 * error location by freeing the error and resetting the location to

 * %NULL. To display an error to the user, simply display the @message,

 * perhaps along with additional context known only to the calling

 * function (the file being opened, or whatever - though in the

 * g_file_get_contents() case, the @message already contains a filename).

 *

 * When implementing a function that can report errors, the basic

 * tool is g_set_error(). Typically, if a fatal error occurs you

 * want to g_set_error(), then return immediately. g_set_error()

 * does nothing if the error location passed to it is %NULL.

 * Here's an example:

 * |[

 * gint

 * foo_open_file (GError **error)

 * {

 *   gint fd;

 *   int saved_errno;

 *

 *   fd = open ("file.txt", O_RDONLY);

 *   saved_errno = errno;

 *

 *   if (fd < 0)

 *     {

 *       g_set_error (error,

 *                    FOO_ERROR,                 // error domain

 *                    FOO_ERROR_BLAH,            // error code

 *                    "Failed to open file: %s", // error message format string

 *                    g_strerror (saved_errno));

 *       return -1;

 *     }

 *   else

 *     return fd;

 * }

 * ]|

 *

 * Things are somewhat more complicated if you yourself call another

 * function that can report a #GError. If the sub-function indicates

 * fatal errors in some way other than reporting a #GError, such as

 * by returning %TRUE on success, you can simply do the following:

 * |[

 * gboolean

 * my_function_that_can_fail (GError **err)

 * {

 *   g_return_val_if_fail (err == NULL || *err == NULL, FALSE);

 *

 *   if (!sub_function_that_can_fail (err))

 *     {

 *       // assert that error was set by the sub-function

 *       g_assert (err == NULL || *err != NULL);

 *       return FALSE;

 *     }

 *

 *   // otherwise continue, no error occurred

 *   g_assert (err == NULL || *err == NULL);

 * }

 * ]|

 *

 * If the sub-function does not indicate errors other than by

 * reporting a #GError (or if its return value does not reliably indicate

 * errors) you need to create a temporary #GError

 * since the passed-in one may be %NULL. g_propagate_error() is

 * intended for use in this case.

 * |[

 * gboolean

 * my_function_that_can_fail (GError **err)

 * {

 *   GError *tmp_error;

 *

 *   g_return_val_if_fail (err == NULL || *err == NULL, FALSE);

 *

 *   tmp_error = NULL;

 *   sub_function_that_can_fail (&tmp_error);

 *

 *   if (tmp_error != NULL)

 *     {

 *       // store tmp_error in err, if err != NULL,

 *       // otherwise call g_error_free() on tmp_error

 *       g_propagate_error (err, tmp_error);

 *       return FALSE;

 *     }

 *

 *   // otherwise continue, no error occurred

 * }

 * ]|

 *

 * Error pileups are always a bug. For example, this code is incorrect:

 * |[

 * gboolean

 * my_function_that_can_fail (GError **err)

 * {

 *   GError *tmp_error;

 *

 *   g_return_val_if_fail (err == NULL || *err == NULL, FALSE);

 *

 *   tmp_error = NULL;

 *   sub_function_that_can_fail (&tmp_error);

 *   other_function_that_can_fail (&tmp_error);

 *

 *   if (tmp_error != NULL)

 *     {

 *       g_propagate_error (err, tmp_error);

 *       return FALSE;

 *     }

 * }

 * ]|

 * @tmp_error should be checked immediately after sub_function_that_can_fail(),

 * and either cleared or propagated upward. The rule is: after each error,

 * you must either handle the error, or return it to the calling function.

 *

 * Note that passing %NULL for the error location is the equivalent

 * of handling an error by always doing nothing about it. So the

 * following code is fine, assuming errors in sub_function_that_can_fail()

 * are not fatal to my_function_that_can_fail():

 * |[

 * gboolean

 * my_function_that_can_fail (GError **err)

 * {

 *   GError *tmp_error;

 *

 *   g_return_val_if_fail (err == NULL || *err == NULL, FALSE);

 *

 *   sub_function_that_can_fail (NULL); // ignore errors

 *

 *   tmp_error = NULL;

 *   other_function_that_can_fail (&tmp_error);

 *

 *   if (tmp_error != NULL)

 *     {

 *       g_propagate_error (err, tmp_error);

 *       return FALSE;

 *     }

 * }

 * ]|

 *

 * Note that passing %NULL for the error location ignores errors;

 * it's equivalent to

 * `try { sub_function_that_can_fail (); } catch (...) {}`

 * in C++. It does not mean to leave errors unhandled; it means

 * to handle them by doing nothing.

 *

 * Error domains and codes are conventionally named as follows:

 *

 * - The error domain is called <NAMESPACE>_<MODULE>_ERROR,

 *   for example %G_SPAWN_ERROR or %G_THREAD_ERROR:

 *   |[

 *   #define G_SPAWN_ERROR g_spawn_error_quark ()

 *

 *   GQuark

 *   g_spawn_error_quark (void)

 *   {

 *       return g_quark_from_static_string ("g-spawn-error-quark");

 *   }

 *   ]|

 *

 * - The quark function for the error domain is called

 *   <namespace>_<module>_error_quark,

 *   for example g_spawn_error_quark() or g_thread_error_quark().

 *

 * - The error codes are in an enumeration called

 *   <Namespace><Module>Error;

 *   for example, #GThreadError or #GSpawnError.

 *

 * - Members of the error code enumeration are called

 *   <NAMESPACE>_<MODULE>_ERROR_,

 *   for example %G_SPAWN_ERROR_FORK or %G_THREAD_ERROR_AGAIN.

 *

 * - If there's a "generic" or "unknown" error code for unrecoverable

 *   errors it doesn't make sense to distinguish with specific codes,

 *   it should be called <NAMESPACE>_<MODULE>_ERROR_FAILED,

 *   for example %G_SPAWN_ERROR_FAILED. In the case of error code

 *   enumerations that may be extended in future releases, you should

 *   generally not handle this error code explicitly, but should

 *   instead treat any unrecognized error code as equivalent to

 *   FAILED.

 *

 * ## Comparison of #GError and traditional error handling # {#gerror-comparison}

 *

 * #GError has several advantages over traditional numeric error codes:

 * importantly, tools like

 * [gobject-introspection](https://developer.gnome.org/gi/stable/) understand

 * #GErrors and convert them to exceptions in bindings; the message includes

 * more information than just a code; and use of a domain helps prevent

 * misinterpretation of error codes.

 *

 * #GError has disadvantages though: it requires a memory allocation, and

 * formatting the error message string has a performance overhead. This makes it

 * unsuitable for use in retry loops where errors are a common case, rather than

 * being unusual. For example, using %G_IO_ERROR_WOULD_BLOCK means hitting these

 * overheads in the normal control flow. String formatting overhead can be

 * eliminated by using g_set_error_literal() in some cases.

 *

 * These performance issues can be compounded if a function wraps the #GErrors

 * returned by the functions it calls: this multiplies the number of allocations

 * and string formatting operations. This can be partially mitigated by using

 * g_prefix_error().

 *

 * ## Rules for use of #GError # {#gerror-rules}

 *

 * Summary of rules for use of #GError:

 *

 * - Do not report programming errors via #GError.

 * 

 * - The last argument of a function that returns an error should

 *   be a location where a #GError can be placed (i.e. "#GError** error").

 *   If #GError is used with varargs, the #GError** should be the last

 *   argument before the "...".

 *

 * - The caller may pass %NULL for the #GError** if they are not interested

 *   in details of the exact error that occurred.

 *

 * - If %NULL is passed for the #GError** argument, then errors should

 *   not be returned to the caller, but your function should still

 *   abort and return if an error occurs. That is, control flow should

 *   not be affected by whether the caller wants to get a #GError.

 *

 * - If a #GError is reported, then your function by definition had a

 *   fatal failure and did not complete whatever it was supposed to do.

 *   If the failure was not fatal, then you handled it and you should not

 *   report it. If it was fatal, then you must report it and discontinue

 *   whatever you were doing immediately.

 *

 * - If a #GError is reported, out parameters are not guaranteed to

 *   be set to any defined value.

 *

 * - A #GError* must be initialized to %NULL before passing its address

 *   to a function that can report errors.

 *

 * - "Piling up" errors is always a bug. That is, if you assign a

 *   new #GError to a #GError* that is non-%NULL, thus overwriting

 *   the previous error, it indicates that you should have aborted

 *   the operation instead of continuing. If you were able to continue,

 *   you should have cleared the previous error with g_clear_error().

 *   g_set_error() will complain if you pile up errors.

 *

 * - By convention, if you return a boolean value indicating success

 *   then %TRUE means success and %FALSE means failure. Avoid creating

 *   functions which have a boolean return value and a GError parameter,

 *   but where the boolean does something other than signal whether the

 *   GError is set.  Among other problems, it requires C callers to allocate

 *   a temporary error.  Instead, provide a "gboolean *" out parameter.

 *   There are functions in GLib itself such as g_key_file_has_key() that

 *   are deprecated because of this. If %FALSE is returned, the error must

 *   be set to a non-%NULL value.  One exception to this is that in situations

 *   that are already considered to be undefined behaviour (such as when a

 *   g_return_val_if_fail() check fails), the error need not be set.

 *   Instead of checking separately whether the error is set, callers

 *   should ensure that they do not provoke undefined behaviour, then

 *   assume that the error will be set on failure.

 *

 * - A %NULL return value is also frequently used to mean that an error

 *   occurred. You should make clear in your documentation whether %NULL

 *   is a valid return value in non-error cases; if %NULL is a valid value,

 *   then users must check whether an error was returned to see if the

 *   function succeeded.

 *

 * - When implementing a function that can report errors, you may want

 *   to add a check at the top of your function that the error return

 *   location is either %NULL or contains a %NULL error (e.g.

 *   `g_return_if_fail (error == NULL || *error == NULL);`).

 */

#include "config.h"

#include "gerror.h"

#include "gslice.h"

#include "gstrfuncs.h"

#include "gtestutils.h"

/**

 * g_error_new_valist:

 * @domain: error domain

 * @code: error code

 * @format: printf()-style format for error message

 * @args: #va_list of parameters for the message format

 *

 * Creates a new #GError with the given @domain and @code,

 * and a message formatted with @format.

 *

 * Returns: a new #GError

 *

 * Since: 2.22

 */

GError*

g_error_new_valist (GQuark       domain,

                    gint         code,

                    const gchar *format,

                    va_list      args)

{

  GError *error;

  /* Historically, GError allowed this (although it was never meant to work),

   * and it has significant use in the wild, which g_return_val_if_fail

   * would break. It should maybe g_return_val_if_fail in GLib 4.

   * (GNOME#660371, GNOME#560482)

   */

  g_warn_if_fail (domain != 0);

  g_warn_if_fail (format != NULL);

  error = g_slice_new (GError);

  error->domain = domain;

  error->code = code;

  error->message = g_strdup_vprintf (format, args);

  return error;

}

/**

 * g_error_new:

 * @domain: error domain

 * @code: error code

 * @format: printf()-style format for error message

 * @...: parameters for message format

 *

 * Creates a new #GError with the given @domain and @code,

 * and a message formatted with @format.

 *

 * Returns: a new #GError

 */

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;

}

/**

 * g_error_new_literal:

 * @domain: error domain

 * @code: error code

 * @message: error message

 *

 * Creates a new #GError; unlike g_error_new(), @message is

 * not a printf()-style format string. Use this function if

 * @message contains text you don't have control over,

 * that could include printf() escape sequences.

 *

 * Returns: a new #GError

 **/

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_slice_new (GError);

  err->domain = domain;

  err->code = code;

  err->message = g_strdup (message);

  return err;

}

/**

 * g_error_free:

 * @error: a #GError

 *

 * Frees a #GError and associated resources.

 */

void

g_error_free (GError *error)

{

  g_return_if_fail (error != NULL);

  g_free (error->message);

  g_slice_free (GError, error);

}

/**

 * g_error_copy:

 * @error: a #GError

 *

 * Makes a copy of @error.

 *

 * Returns: a new #GError

 */

GError*

g_error_copy (const GError *error)

{

  GError *copy;

  g_return_val_if_fail (error != NULL, NULL);

  /* See g_error_new_valist for why these don't return */

  g_warn_if_fail (error->domain != 0);

  g_warn_if_fail (error->message != NULL);

  copy = g_slice_new (GError);

  *copy = *error;

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

  return copy;

}

/**

 * g_error_matches:

 * @error: (nullable): a #GError

 * @domain: an error domain

 * @code: an error code

 *

 * Returns %TRUE if @error matches @domain and @code, %FALSE

 * otherwise. In particular, when @error is %NULL, %FALSE will

 * be returned.

 *

 * If @domain contains a `FAILED` (or otherwise generic) error code,

 * you should generally not check for it explicitly, but should

 * instead treat any not-explicitly-recognized error code as being

 * equivalent to the `FAILED` code. This way, if the domain is

 * extended in the future to provide a more specific error code for

 * a certain case, your code will still work.

 *

 * Returns: whether @error has @domain and @code

 */

gboolean

g_error_matches (const GError *error,

                 GQuark        domain,

                 gint          code)

{

  return error &&

    error->domain == domain &&

    error->code == code;

}

#define ERROR_OVERWRITTEN_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.\n" \

               "The overwriting error message was: %s"

/**

 * g_set_error:

 * @err: (out callee-allocates) (optional): a return location for a #GError

 * @domain: error domain

 * @code: error code

 * @format: printf()-style format

 * @...: args for @format

 *

 * Does nothing if @err is %NULL; if @err is non-%NULL, then *@err

 * must be %NULL. A new #GError is created and assigned to *@err.

 */

void

g_set_error (GError      **err,

             GQuark        domain,

             gint          code,

             const gchar  *format,

             ...)

{

  GError *new;

  va_list args;

  if (err == NULL)

    return;

  va_start (args, format);

  new = g_error_new_valist (domain, code, format, args);

  va_end (args);

  if (*err == NULL)

    *err = new;

  else

    {

      g_warning (ERROR_OVERWRITTEN_WARNING, new->message);

      g_error_free (new);

    }

}

/**

 * g_set_error_literal:

 * @err: (out callee-allocates) (optional): a return location for a #GError

 * @domain: error domain

 * @code: error code

 * @message: error message

 *

 * Does nothing if @err is %NULL; if @err is non-%NULL, then *@err

 * must be %NULL. A new #GError is created and assigned to *@err.

 * Unlike g_set_error(), @message is not a printf()-style format string.

 * Use this function if @message contains text you don't have control over,

 * that could include printf() escape sequences.

 *

 * Since: 2.18

 */

void

g_set_error_literal (GError      **err,

                     GQuark        domain,

                     gint          code,

                     const gchar  *message)

{

  if (err == NULL)

    return;

  if (*err == NULL)

    *err = g_error_new_literal (domain, code, message);

  else

    g_warning (ERROR_OVERWRITTEN_WARNING, message);

}

/**

 * g_propagate_error:

 * @dest: (out callee-allocates) (optional) (nullable): error return location

 * @src: (transfer full): error to move into the return location

 *

 * If @dest is %NULL, free @src; otherwise, moves @src into *@dest.

 * The error variable @dest points to must be %NULL.

 *

 * @src must be non-%NULL.

 *

 * Note that @src is no longer valid after this call. If you want

 * to keep using the same GError*, you need to set it to %NULL

 * after calling this function on it.

 */

void

g_propagate_error (GError **dest,

		   GError  *src)

{

  g_return_if_fail (src != NULL);

  if (dest == NULL)

    {

      if (src)

        g_error_free (src);

      return;

    }

  else

    {

      if (*dest != NULL)

        {

          g_warning (ERROR_OVERWRITTEN_WARNING, src->message);

          g_error_free (src);

        }

      else

        *dest = src;

    }

}

/**

 * g_clear_error:

 * @err: a #GError return location

 *

 * If @err or *@err is %NULL, does nothing. Otherwise,

 * calls g_error_free() on *@err and sets *@err to %NULL.

 */

void

g_clear_error (GError **err)

{

  if (err && *err)

    {

      g_error_free (*err);

      *err = NULL;

    }

}

G_GNUC_PRINTF(2, 0)

static void

g_error_add_prefix (gchar       **string,

                    const gchar  *format,

                    va_list       ap)

{

  gchar *oldstring;

  gchar *prefix;

  prefix = g_strdup_vprintf (format, ap);

  oldstring = *string;

  *string = g_strconcat (prefix, oldstring, NULL);

  g_free (oldstring);

  g_free (prefix);

}

/**

 * g_prefix_error:

 * @err: (inout) (optional) (nullable): a return location for a #GError

 * @format: printf()-style format string

 * @...: arguments to @format

 *

 * Formats a string according to @format and prefix it to an existing

 * error message. If @err is %NULL (ie: no error variable) then do

 * nothing.

 *

 * If *@err is %NULL (ie: an error variable is present but there is no

 * error condition) then also do nothing.

 *

 * Since: 2.16

 */

void

g_prefix_error (GError      **err,

                const gchar  *format,

                ...)

{

  if (err && *err)

    {

      va_list ap;

      va_start (ap, format);

      g_error_add_prefix (&(*err)->message, format, ap);

      va_end (ap);

    }

}

/**

 * g_propagate_prefixed_error:

 * @dest: error return location

 * @src: error to move into the return location

 * @format: printf()-style format string

 * @...: arguments to @format

 *

 * If @dest is %NULL, free @src; otherwise, moves @src into *@dest.

 * *@dest must be %NULL. After the move, add a prefix as with

 * g_prefix_error().

 *

 * Since: 2.16

 **/

void

g_propagate_prefixed_error (GError      **dest,

                            GError       *src,

                            const gchar  *format,

                            ...)

{

  g_propagate_error (dest, src);

  if (dest && *dest)

    {

      va_list ap;

      va_start (ap, format);

      g_error_add_prefix (&(*dest)->message, format, ap);

      va_end (ap);

    }

}