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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Debugging</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="index.html" title="GStreamer Plugin Writer's Guide (1.10.4)"><link rel="up" href="chapter-checklist-element.html" title="Chapter 27. Things to check when writing an element"><link rel="prev" href="chapter-checklist-element.html" title="Chapter 27. Things to check when writing an element"><link rel="next" href="section-checklist-query.html" title="Querying, events and the like"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Debugging</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="chapter-checklist-element.html">Prev</a> </td><th width="60%" align="center">Chapter 27. Things to check when writing an element</th><td width="20%" align="right"> <a accesskey="n" href="section-checklist-query.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="section-checklist-debug"></a>Debugging</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Elements should <span class="emphasis"><em>never</em></span> use their standard
output for debugging (using functions such as <code class="function">printf
()</code> or <code class="function">g_print ()</code>). Instead,
elements should use the logging functions provided by <span class="application">GStreamer</span>,
named <code class="function">GST_DEBUG ()</code>,
<code class="function">GST_LOG ()</code>, <code class="function">GST_INFO ()</code>,
<code class="function">GST_WARNING ()</code> and
<code class="function">GST_ERROR ()</code>. The various logging levels can
be turned on and off at runtime and can thus be used for solving
issues as they turn up. Instead of <code class="function">GST_LOG ()</code>
(as an example), you can also use <code class="function">GST_LOG_OBJECT
()</code> to print the object that you're logging output for.
</p></li><li class="listitem"><p>
Ideally, elements should use their own debugging category. Most
elements use the following code to do that:
</p><pre class="programlisting">
GST_DEBUG_CATEGORY_STATIC (myelement_debug);
#define GST_CAT_DEFAULT myelement_debug
[..]
static void
gst_myelement_class_init (GstMyelementClass *klass)
{
[..]
GST_DEBUG_CATEGORY_INIT (myelement_debug, "myelement",
0, "My own element");
}
</pre><p>
At runtime, you can turn on debugging using the commandline
option <span class="command"><strong>--gst-debug=myelement:5</strong></span>.
</p></li><li class="listitem"><p>
Elements should use GST_DEBUG_FUNCPTR when setting pad functions or
overriding element class methods, for example:
</p><pre class="programlisting">
gst_pad_set_event_func (myelement->srcpad,
GST_DEBUG_FUNCPTR (my_element_src_event));
</pre><p>
This makes debug output much easier to read later on.
</p></li><li class="listitem"><p>
Elements that are aimed for inclusion into one of the GStreamer
modules should ensure consistent naming of the element name,
structures and function names. For example, if the element type is
GstYellowFooDec, functions should be prefixed with
gst_yellow_foo_dec_ and the element should be registered
as 'yellowfoodec'. Separate words should be separate in this scheme,
so it should be GstFooDec and gst_foo_dec, and not GstFoodec and
gst_foodec.
</p></li></ul></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="chapter-checklist-element.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="chapter-checklist-element.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="section-checklist-query.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 27. Things to check when writing an element </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Querying, events and the like</td></tr></table></div></body></html>
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