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| <h5 class="subsubsection">23.3.3.15 Accessing inferior stack frames from Guile.</h5> |
| |
| <p><a name="index-frames-in-guile-2674"></a>When the debugged program stops, <span class="sc">gdb</span> is able to analyze its call |
| stack (see <a href="Frames.html#Frames">Stack frames</a>). The <code><gdb:frame></code> class |
| represents a frame in the stack. A <code><gdb:frame></code> object is only valid |
| while its corresponding frame exists in the inferior's stack. If you try |
| to use an invalid frame object, <span class="sc">gdb</span> will throw a |
| <code>gdb:invalid-object</code> exception (see <a href="Guile-Exception-Handling.html#Guile-Exception-Handling">Guile Exception Handling</a>). |
| |
| <p>Two <code><gdb:frame></code> objects can be compared for equality with the |
| <code>equal?</code> function, like: |
| |
| <pre class="smallexample"> (gdb) guile (equal? (newest-frame) (selected-frame)) |
| #t |
| </pre> |
| <p>The following frame-related procedures are provided by the |
| <code>(gdb)</code> module: |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame?</b><var> object<a name="index-frame_003f-2675"></a></var><br> |
| <blockquote><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:frame></code> object. |
| Otherwise return <code>#f</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-valid?</b><var> frame<a name="index-frame_002dvalid_003f-2676"></a></var><br> |
| <blockquote><p>Returns <code>#t</code> if <var>frame</var> is valid, <code>#f</code> if not. |
| A frame object can become invalid if the frame it refers to doesn't |
| exist anymore in the inferior. All <code><gdb:frame></code> procedures will throw |
| an exception if the frame is invalid at the time the procedure is called. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-name</b><var> frame<a name="index-frame_002dname-2677"></a></var><br> |
| <blockquote><p>Return the function name of <var>frame</var>, or <code>#f</code> if it can't be |
| obtained. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-arch</b><var> frame<a name="index-frame_002darch-2678"></a></var><br> |
| <blockquote><p>Return the <code><gdb:architecture></code> object corresponding to <var>frame</var>'s |
| architecture. See <a href="Architectures-In-Guile.html#Architectures-In-Guile">Architectures In Guile</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-type</b><var> frame<a name="index-frame_002dtype-2679"></a></var><br> |
| <blockquote><p>Return the type of <var>frame</var>. The value can be one of: |
| |
| <dl> |
| <dt><code>NORMAL_FRAME</code><dd>An ordinary stack frame. |
| |
| <br><dt><code>DUMMY_FRAME</code><dd>A fake stack frame that was created by <span class="sc">gdb</span> when performing an |
| inferior function call. |
| |
| <br><dt><code>INLINE_FRAME</code><dd>A frame representing an inlined function. The function was inlined |
| into a <code>NORMAL_FRAME</code> that is older than this one. |
| |
| <br><dt><code>TAILCALL_FRAME</code><dd>A frame representing a tail call. See <a href="Tail-Call-Frames.html#Tail-Call-Frames">Tail Call Frames</a>. |
| |
| <br><dt><code>SIGTRAMP_FRAME</code><dd>A signal trampoline frame. This is the frame created by the OS when |
| it calls into a signal handler. |
| |
| <br><dt><code>ARCH_FRAME</code><dd>A fake stack frame representing a cross-architecture call. |
| |
| <br><dt><code>SENTINEL_FRAME</code><dd>This is like <code>NORMAL_FRAME</code>, but it is only used for the |
| newest frame. |
| </dl> |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-unwind-stop-reason</b><var> frame<a name="index-frame_002dunwind_002dstop_002dreason-2680"></a></var><br> |
| <blockquote><p>Return an integer representing the reason why it's not possible to find |
| more frames toward the outermost frame. Use |
| <code>unwind-stop-reason-string</code> to convert the value returned by this |
| function to a string. The value can be one of: |
| |
| <dl> |
| <dt><code>FRAME_UNWIND_NO_REASON</code><dd>No particular reason (older frames should be available). |
| |
| <br><dt><code>FRAME_UNWIND_NULL_ID</code><dd>The previous frame's analyzer returns an invalid result. |
| |
| <br><dt><code>FRAME_UNWIND_OUTERMOST</code><dd>This frame is the outermost. |
| |
| <br><dt><code>FRAME_UNWIND_UNAVAILABLE</code><dd>Cannot unwind further, because that would require knowing the |
| values of registers or memory that have not been collected. |
| |
| <br><dt><code>FRAME_UNWIND_INNER_ID</code><dd>This frame ID looks like it ought to belong to a NEXT frame, |
| but we got it for a PREV frame. Normally, this is a sign of |
| unwinder failure. It could also indicate stack corruption. |
| |
| <br><dt><code>FRAME_UNWIND_SAME_ID</code><dd>This frame has the same ID as the previous one. That means |
| that unwinding further would almost certainly give us another |
| frame with exactly the same ID, so break the chain. Normally, |
| this is a sign of unwinder failure. It could also indicate |
| stack corruption. |
| |
| <br><dt><code>FRAME_UNWIND_NO_SAVED_PC</code><dd>The frame unwinder did not find any saved PC, but we needed |
| one to unwind further. |
| |
| <br><dt><code>FRAME_UNWIND_MEMORY_ERROR</code><dd>The frame unwinder caused an error while trying to access memory. |
| |
| <br><dt><code>FRAME_UNWIND_FIRST_ERROR</code><dd>Any stop reason greater or equal to this value indicates some kind |
| of error. This special value facilitates writing code that tests |
| for errors in unwinding in a way that will work correctly even if |
| the list of the other values is modified in future <span class="sc">gdb</span> |
| versions. Using it, you could write: |
| |
| <pre class="smallexample"> (define reason (frame-unwind-stop-readon (selected-frame))) |
| (define reason-str (unwind-stop-reason-string reason)) |
| (if (>= reason FRAME_UNWIND_FIRST_ERROR) |
| (format #t "An error occured: ~s\n" reason-str)) |
| </pre> |
| </dl> |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-pc</b><var> frame<a name="index-frame_002dpc-2681"></a></var><br> |
| <blockquote><p>Return the frame's resume address. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-block</b><var> frame<a name="index-frame_002dblock-2682"></a></var><br> |
| <blockquote><p>Return the frame's code block as a <code><gdb:block></code> object. |
| See <a href="Blocks-In-Guile.html#Blocks-In-Guile">Blocks In Guile</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-function</b><var> frame<a name="index-frame_002dfunction-2683"></a></var><br> |
| <blockquote><p>Return the symbol for the function corresponding to this frame |
| as a <code><gdb:symbol></code> object, or <code>#f</code> if there isn't one. |
| See <a href="Symbols-In-Guile.html#Symbols-In-Guile">Symbols In Guile</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-older</b><var> frame<a name="index-frame_002dolder-2684"></a></var><br> |
| <blockquote><p>Return the frame that called <var>frame</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-newer</b><var> frame<a name="index-frame_002dnewer-2685"></a></var><br> |
| <blockquote><p>Return the frame called by <var>frame</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-sal</b><var> frame<a name="index-frame_002dsal-2686"></a></var><br> |
| <blockquote><p>Return the frame's <code><gdb:sal></code> (symtab and line) object. |
| See <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile">Symbol Tables In Guile</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-read-register</b><var> frame register<a name="index-frame_002dread_002dregister-2687"></a></var><br> |
| <blockquote><p>Return the value of <var>register</var> in <var>frame</var>. <var>register</var> |
| should be a string, like ‘<samp><span class="samp">pc</span></samp>’. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-read-var</b><var> frame variable </var><span class="roman">[</span><var>#:block block</var><span class="roman">]</span><var><a name="index-frame_002dread_002dvar-2688"></a></var><br> |
| <blockquote><p>Return the value of <var>variable</var> in <var>frame</var>. If the optional |
| argument <var>block</var> is provided, search for the variable from that |
| block; otherwise start at the frame's current block (which is |
| determined by the frame's current program counter). The |
| <var>variable</var> must be given as a string or a <code><gdb:symbol></code> |
| object, and <var>block</var> must be a <code><gdb:block></code> object. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>frame-select</b><var> frame<a name="index-frame_002dselect-2689"></a></var><br> |
| <blockquote><p>Set <var>frame</var> to be the selected frame. See <a href="Stack.html#Stack">Examining the Stack</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>selected-frame</b><var><a name="index-selected_002dframe-2690"></a></var><br> |
| <blockquote><p>Return the selected frame object. See <a href="Selection.html#Selection">Selecting a Frame</a>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>newest-frame</b><var><a name="index-newest_002dframe-2691"></a></var><br> |
| <blockquote><p>Return the newest frame object for the selected thread. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>unwind-stop-reason-string</b><var> reason<a name="index-unwind_002dstop_002dreason_002dstring-2692"></a></var><br> |
| <blockquote><p>Return a string explaining the reason why <span class="sc">gdb</span> stopped unwinding |
| frames, as expressed by the given <var>reason</var> code (an integer, see the |
| <code>frame-unwind-stop-reason</code> procedure above in this section). |
| </p></blockquote></div> |
| |
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