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Use the current g_file_get_contents() as example.

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This commit is contained in:
Matthias Clasen 2003-06-04 22:49:08 +00:00
parent fef203f9f7
commit 99c0940b78
1 changed files with 9 additions and 8 deletions
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17
docs/reference/glib/tmpl/error_reporting.sgml
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@ -39,14 +39,17 @@ 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. Functions that can fail take a return location for a #GError as their last argument.
For example: For example:
<informalexample><programlisting> <informalexample><programlisting>
gchar* g_file_get_contents (const gchar *filename, GError **error); gboolean g_file_get_contents (const gchar *filename,
gchar **contents,
gsize *length,
GError **error);
</programlisting></informalexample> </programlisting></informalexample>
If you pass a non-%NULL value for the <literal>error</literal> argument, it should If you pass a non-%NULL value for the <literal>error</literal> argument, it should
point to a location where an error can be placed. For example: point to a location where an error can be placed. For example:
<informalexample><programlisting> <informalexample><programlisting>
gchar *contents; gchar *contents;
GError *err = NULL; GError *err = NULL;
contents = g_file_get_contents ("foo.txt", &amp;err); g_file_get_contents ("foo.txt", &amp;contents, NULL, &amp;err);
g_assert ((contents == NULL &amp;&amp; err != NULL) || (contents != NULL &amp;&amp; err == NULL)); g_assert ((contents == NULL &amp;&amp; err != NULL) || (contents != NULL &amp;&amp; err == NULL));
if (err != NULL) if (err != NULL)
{ {
@ -63,18 +66,16 @@ else
</programlisting></informalexample> </programlisting></informalexample>
Note that <literal>err != NULL</literal> in this example is a Note that <literal>err != NULL</literal> in this example is a
<emphasis>reliable</emphasis> indicator of whether <emphasis>reliable</emphasis> indicator of whether
g_file_get_contents() failed. Also, g_file_get_contents() uses the g_file_get_contents() failed. Additionally, g_file_get_contents() returns
convention that a %NULL return value means an error occurred (but not a boolean which indicates whether it was successful.
all functions use this convention).
</para> </para>
<para> <para>
Because g_file_get_contents() returns %NULL on failure, if you are only 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 interested in whether it failed and don't need to display an error message, you
can pass %NULL for the <literal>error</literal> argument: can pass %NULL for the <literal>error</literal> argument:
<informalexample><programlisting> <informalexample><programlisting>
contents = g_file_get_contents ("foo.txt", NULL); /* ignore errors */ if (g_file_get_contents ("foo.txt", &contents, NULL, NULL)) /* ignore errors */
if (contents != NULL)
/* no error occurred */ ; /* no error occurred */ ;
else else
/* error */ ; /* error */ ;