175 lines
9.4 KiB
HTML
175 lines
9.4 KiB
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<!DOCTYPE html>
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<html>
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<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>High-Level Traps (Guile Reference Manual)</title>
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<meta name="description" content="High-Level Traps (Guile Reference Manual)">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Traps.html" rel="up" title="Traps">
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<link href="Trap-States.html" rel="prev" title="Trap States">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="High_002dLevel-Traps">
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<div class="nav-panel">
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<p>
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Previous: <a href="Trap-States.html" accesskey="p" rel="prev">Trap States</a>, Up: <a href="Traps.html" accesskey="u" rel="up">Traps</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsubsection" id="High_002dLevel-Traps-1"><span>6.26.4.6 High-Level Traps<a class="copiable-link" href="#High_002dLevel-Traps-1"> ¶</a></span></h4>
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<p>The low-level trap API allows one to make traps that call procedures,
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and the trap state API allows one to keep track of what traps are
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there. But neither of these APIs directly helps you when you want to
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set a breakpoint, because it’s unclear what to do when the trap fires.
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Do you enter a debugger, or mail a summary of the situation to your
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great-aunt, or what?
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</p>
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<p>So for the common case in which you just want to install breakpoints,
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and then have them all result in calls to one parameterizable procedure,
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we have the high-level trap interface.
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</p>
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<p>Perhaps we should have started this section with this interface, as it’s
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clearly the one most people should use. But as its capabilities and
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limitations proceed from the lower layers, we felt that the
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character-building exercise of building a mental model might be helpful.
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</p>
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<p>These procedures share a module with trap states:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(use-modules (system vm trap-state))
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-with_002ddefault_002dtrap_002dhandler"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">with-default-trap-handler</strong> <var class="def-var-arguments">handler thunk</var><a class="copiable-link" href="#index-with_002ddefault_002dtrap_002dhandler"> ¶</a></span></dt>
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<dd><p>Call <var class="var">thunk</var> in a dynamic context in which <var class="var">handler</var> is the
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current trap handler.
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</p>
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<p>Additionally, during the execution of <var class="var">thunk</var>, the VM trace level
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(see <a class="pxref" href="VM-Hooks.html">VM Hooks</a>) is set to the number of enabled traps. This ensures
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that traps will in fact fire.
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</p>
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<p><var class="var">handler</var> may be <code class="code">#f</code>, in which case VM hooks are not enabled
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as they otherwise would be, as there is nothing to handle the traps.
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</p></dd></dl>
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<p>The trace-level-setting behavior of <code class="code">with-default-trap-handler</code> is
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one of its more useful aspects, but if you are willing to forgo that,
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and just want to install a global trap handler, there’s a function for
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that too:
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-install_002dtrap_002dhandler_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">install-trap-handler!</strong> <var class="def-var-arguments">handler</var><a class="copiable-link" href="#index-install_002dtrap_002dhandler_0021"> ¶</a></span></dt>
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<dd><p>Set the current thread’s trap handler to <var class="var">handler</var>.
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</p></dd></dl>
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<p>Trap handlers are called when traps installed by procedures from this
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module fire. The current “consumer” of this API is Guile’s REPL, but
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one might easily imagine other trap handlers being used to integrate
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with other debugging tools.
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</p>
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<a class="index-entry-id" id="index-Breakpoints-1"></a>
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<a class="index-entry-id" id="index-Setting-breakpoints"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-add_002dtrap_002dat_002dprocedure_002dcall_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">add-trap-at-procedure-call!</strong> <var class="def-var-arguments">proc</var><a class="copiable-link" href="#index-add_002dtrap_002dat_002dprocedure_002dcall_0021"> ¶</a></span></dt>
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<dd><p>Install a trap that will fire when <var class="var">proc</var> is called.
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</p>
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<p>This is a breakpoint.
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</p></dd></dl>
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<a class="index-entry-id" id="index-Tracepoints"></a>
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<a class="index-entry-id" id="index-Setting-tracepoints"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-add_002dtrace_002dat_002dprocedure_002dcall_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">add-trace-at-procedure-call!</strong> <var class="def-var-arguments">proc</var><a class="copiable-link" href="#index-add_002dtrace_002dat_002dprocedure_002dcall_0021"> ¶</a></span></dt>
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<dd><p>Install a trap that will print a tracing message when <var class="var">proc</var> is
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called. See <a class="xref" href="Tracing-Traps.html">Tracing Traps</a>, for more information.
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</p>
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<p>This is a tracepoint.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-add_002dtrap_002dat_002dsource_002dlocation_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">add-trap-at-source-location!</strong> <var class="def-var-arguments">file user-line</var><a class="copiable-link" href="#index-add_002dtrap_002dat_002dsource_002dlocation_0021"> ¶</a></span></dt>
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<dd><p>Install a trap that will fire when control reaches the given source
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location. <var class="var">user-line</var> is one-indexed, as users count lines, instead
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of zero-indexed, as Guile counts lines.
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</p>
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<p>This is a source breakpoint.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-add_002dephemeral_002dtrap_002dat_002dframe_002dfinish_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">add-ephemeral-trap-at-frame-finish!</strong> <var class="def-var-arguments">frame handler</var><a class="copiable-link" href="#index-add_002dephemeral_002dtrap_002dat_002dframe_002dfinish_0021"> ¶</a></span></dt>
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<dd><p>Install a trap that will call <var class="var">handler</var> when <var class="var">frame</var> finishes
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executing. The trap will be removed from the trap state after firing, or
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on nonlocal exit.
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</p>
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<p>This is a finish trap, used to implement the “finish” REPL command.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-add_002dephemeral_002dstepping_002dtrap_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">add-ephemeral-stepping-trap!</strong> <var class="def-var-arguments">frame handler [#:into?] [#:instruction?]</var><a class="copiable-link" href="#index-add_002dephemeral_002dstepping_002dtrap_0021"> ¶</a></span></dt>
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<dd><p>Install a trap that will call <var class="var">handler</var> after stepping to a
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different source line or instruction. The trap will be removed from the
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trap state after firing, or on nonlocal exit.
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</p>
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<p>If <var class="var">instruction?</var> is false (the default), the trap will fire when
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control reaches a new source line. Otherwise it will fire when control
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reaches a new instruction.
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</p>
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<p>Additionally, if <var class="var">into?</var> is false (not the default), the trap will
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only fire for frames at or prior to the given frame. If <var class="var">into?</var> is
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true (the default), the trap may step into nested procedure
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invocations.
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</p>
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<p>This is a stepping trap, used to implement the “step”, “next”,
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“step-instruction”, and “next-instruction” REPL commands.
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</p></dd></dl>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Previous: <a href="Trap-States.html">Trap States</a>, Up: <a href="Traps.html">Traps</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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