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| <h4 class="subsection">13.2.1 <code>tfind </code><var>n</var></h4> |
| |
| <p><a name="index-tfind-927"></a><a name="index-select-trace-snapshot-928"></a><a name="index-find-trace-snapshot-929"></a>The basic command for selecting a trace snapshot from the buffer is |
| <code>tfind </code><var>n</var>, which finds trace snapshot number <var>n</var>, |
| counting from zero. If no argument <var>n</var> is given, the next |
| snapshot is selected. |
| |
| <p>Here are the various forms of using the <code>tfind</code> command. |
| |
| <dl> |
| <dt><code>tfind start</code><dd>Find the first snapshot in the buffer. This is a synonym for |
| <code>tfind 0</code> (since 0 is the number of the first snapshot). |
| |
| <br><dt><code>tfind none</code><dd>Stop debugging trace snapshots, resume <em>live</em> debugging. |
| |
| <br><dt><code>tfind end</code><dd>Same as ‘<samp><span class="samp">tfind none</span></samp>’. |
| |
| <br><dt><code>tfind</code><dd>No argument means find the next trace snapshot or find the first |
| one if no trace snapshot is selected. |
| |
| <br><dt><code>tfind -</code><dd>Find the previous trace snapshot before the current one. This permits |
| retracing earlier steps. |
| |
| <br><dt><code>tfind tracepoint </code><var>num</var><dd>Find the next snapshot associated with tracepoint <var>num</var>. Search |
| proceeds forward from the last examined trace snapshot. If no |
| argument <var>num</var> is given, it means find the next snapshot collected |
| for the same tracepoint as the current snapshot. |
| |
| <br><dt><code>tfind pc </code><var>addr</var><dd>Find the next snapshot associated with the value <var>addr</var> of the |
| program counter. Search proceeds forward from the last examined trace |
| snapshot. If no argument <var>addr</var> is given, it means find the next |
| snapshot with the same value of PC as the current snapshot. |
| |
| <br><dt><code>tfind outside </code><var>addr1</var><code>, </code><var>addr2</var><dd>Find the next snapshot whose PC is outside the given range of |
| addresses (exclusive). |
| |
| <br><dt><code>tfind range </code><var>addr1</var><code>, </code><var>addr2</var><dd>Find the next snapshot whose PC is between <var>addr1</var> and |
| <var>addr2</var> (inclusive). |
| |
| <br><dt><code>tfind line </code><span class="roman">[</span><var>file</var><code>:</code><span class="roman">]</span><var>n</var><dd>Find the next snapshot associated with the source line <var>n</var>. If |
| the optional argument <var>file</var> is given, refer to line <var>n</var> in |
| that source file. Search proceeds forward from the last examined |
| trace snapshot. If no argument <var>n</var> is given, it means find the |
| next line other than the one currently being examined; thus saying |
| <code>tfind line</code> repeatedly can appear to have the same effect as |
| stepping from line to line in a <em>live</em> debugging session. |
| </dl> |
| |
| <p>The default arguments for the <code>tfind</code> commands are specifically |
| designed to make it easy to scan through the trace buffer. For |
| instance, <code>tfind</code> with no argument selects the next trace |
| snapshot, and <code>tfind -</code> with no argument selects the previous |
| trace snapshot. So, by giving one <code>tfind</code> command, and then |
| simply hitting <RET> repeatedly you can examine all the trace |
| snapshots in order. Or, by saying <code>tfind -</code> and then hitting |
| <RET> repeatedly you can examine the snapshots in reverse order. |
| The <code>tfind line</code> command with no argument selects the snapshot |
| for the next source line executed. The <code>tfind pc</code> command with |
| no argument selects the next snapshot with the same program counter |
| (PC) as the current frame. The <code>tfind tracepoint</code> command with |
| no argument selects the next trace snapshot collected by the same |
| tracepoint as the current one. |
| |
| <p>In addition to letting you scan through the trace buffer manually, |
| these commands make it easy to construct <span class="sc">gdb</span> scripts that |
| scan through the trace buffer and print out whatever collected data |
| you are interested in. Thus, if we want to examine the PC, FP, and SP |
| registers from each trace frame in the buffer, we can say this: |
| |
| <pre class="smallexample"> (gdb) <b>tfind start</b> |
| (gdb) <b>while ($trace_frame != -1)</b> |
| > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \ |
| $trace_frame, $pc, $sp, $fp |
| > tfind |
| > end |
| |
| Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44 |
| Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44 |
| Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44 |
| Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44 |
| Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44 |
| Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44 |
| Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44 |
| Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44 |
| Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44 |
| Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44 |
| Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14 |
| </pre> |
| <p>Or, if we want to examine the variable <code>X</code> at each source line in |
| the buffer: |
| |
| <pre class="smallexample"> (gdb) <b>tfind start</b> |
| (gdb) <b>while ($trace_frame != -1)</b> |
| > printf "Frame %d, X == %d\n", $trace_frame, X |
| > tfind line |
| > end |
| |
| Frame 0, X = 1 |
| Frame 7, X = 2 |
| Frame 13, X = 255 |
| </pre> |
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