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<h3 class="section">13.1 Commands to Set Tracepoints</h3>

<p>Before running such a <dfn>trace experiment</dfn>, an arbitrary number of
tracepoints can be set.  A tracepoint is actually a special type of
breakpoint (see <a href="Set-Breaks.html#Set-Breaks">Set Breaks</a>), so you can manipulate it using
standard breakpoint commands.  For instance, as with breakpoints,
tracepoint numbers are successive integers starting from one, and many
of the commands associated with tracepoints take the tracepoint number
as their argument, to identify which tracepoint to work on.

   <p>For each tracepoint, you can specify, in advance, some arbitrary set
of data that you want the target to collect in the trace buffer when
it hits that tracepoint.  The collected data can include registers,
local variables, or global data.  Later, you can use <span class="sc">gdb</span>
commands to examine the values these data had at the time the
tracepoint was hit.

   <p>Tracepoints do not support every breakpoint feature.  Ignore counts on
tracepoints have no effect, and tracepoints cannot run <span class="sc">gdb</span>
commands when they are hit.  Tracepoints may not be thread-specific
either.

   <p><a name="index-fast-tracepoints-681"></a>Some targets may support <dfn>fast tracepoints</dfn>, which are inserted in
a different way (such as with a jump instead of a trap), that is
faster but possibly restricted in where they may be installed.

   <p><a name="index-static-tracepoints-682"></a><a name="index-markers_002c-static-tracepoints-683"></a><a name="index-probing-markers_002c-static-tracepoints-684"></a>Regular and fast tracepoints are dynamic tracing facilities, meaning
that they can be used to insert tracepoints at (almost) any location
in the target.  Some targets may also support controlling <dfn>static
tracepoints</dfn> from <span class="sc">gdb</span>.  With static tracing, a set of
instrumentation points, also known as <dfn>markers</dfn>, are embedded in
the target program, and can be activated or deactivated by name or
address.  These are usually placed at locations which facilitate
investigating what the target is actually doing.  <span class="sc">gdb</span>'s
support for static tracing includes being able to list instrumentation
points, and attach them with <span class="sc">gdb</span> defined high level
tracepoints that expose the whole range of convenience of
<span class="sc">gdb</span>'s tracepoints support.  Namelly, support for collecting
registers values and values of global or local (to the instrumentation
point) variables; tracepoint conditions and trace state variables. 
The act of installing a <span class="sc">gdb</span> static tracepoint on an
instrumentation point, or marker, is referred to as <dfn>probing</dfn> a
static tracepoint marker.

   <p><code>gdbserver</code> supports tracepoints on some target systems. 
See <a href="Server.html#Server">Tracepoints support in <code>gdbserver</code></a>.

   <p>This section describes commands to set tracepoints and associated
conditions and actions.

<ul class="menu">
<li><a accesskey="1" href="Create-and-Delete-Tracepoints.html#Create-and-Delete-Tracepoints">Create and Delete Tracepoints</a>
<li><a accesskey="2" href="Enable-and-Disable-Tracepoints.html#Enable-and-Disable-Tracepoints">Enable and Disable Tracepoints</a>
<li><a accesskey="3" href="Tracepoint-Passcounts.html#Tracepoint-Passcounts">Tracepoint Passcounts</a>
<li><a accesskey="4" href="Tracepoint-Conditions.html#Tracepoint-Conditions">Tracepoint Conditions</a>
<li><a accesskey="5" href="Trace-State-Variables.html#Trace-State-Variables">Trace State Variables</a>
<li><a accesskey="6" href="Tracepoint-Actions.html#Tracepoint-Actions">Tracepoint Actions</a>
<li><a accesskey="7" href="Listing-Tracepoints.html#Listing-Tracepoints">Listing Tracepoints</a>
<li><a accesskey="8" href="Listing-Static-Tracepoint-Markers.html#Listing-Static-Tracepoint-Markers">Listing Static Tracepoint Markers</a>
<li><a accesskey="9" href="Starting-and-Stopping-Trace-Experiments.html#Starting-and-Stopping-Trace-Experiments">Starting and Stopping Trace Experiments</a>
<li><a href="Tracepoint-Restrictions.html#Tracepoint-Restrictions">Tracepoint Restrictions</a>
</ul>

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