125 lines
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125 lines
6.0 KiB
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<html lang="en">
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<head>
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<title>Rust - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link rel="prev" href="Pascal.html#Pascal" title="Pascal">
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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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<body>
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<div class="node">
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<a name="Rust"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Modula_002d2.html#Modula_002d2">Modula-2</a>,
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Previous: <a rel="previous" accesskey="p" href="Pascal.html#Pascal">Pascal</a>,
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Up: <a rel="up" accesskey="u" href="Supported-Languages.html#Supported-Languages">Supported Languages</a>
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<hr>
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</div>
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<h4 class="subsection">15.4.8 Rust</h4>
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<p><span class="sc">gdb</span> supports the <a href="https://www.rust-lang.org/">Rust Programming Language</a>. Type- and value-printing, and expression
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parsing, are reasonably complete. However, there are a few
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peculiarities and holes to be aware of.
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<ul>
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<li>Linespecs (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>) are never relative to the current
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crate. Instead, they act as if there were a global namespace of
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crates, somewhat similar to the way <code>extern crate</code> behaves.
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<p>That is, if <span class="sc">gdb</span> is stopped at a breakpoint in a function in
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crate ‘<samp><span class="samp">A</span></samp>’, module ‘<samp><span class="samp">B</span></samp>’, then <code>break B::f</code> will attempt
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to set a breakpoint in a function named ‘<samp><span class="samp">f</span></samp>’ in a crate named
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‘<samp><span class="samp">B</span></samp>’.
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<p>As a consequence of this approach, linespecs also cannot refer to
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items using ‘<samp><span class="samp">self::</span></samp>’ or ‘<samp><span class="samp">super::</span></samp>’.
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<li>Because <span class="sc">gdb</span> implements Rust name-lookup semantics in
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expressions, it will sometimes prepend the current crate to a name.
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For example, if <span class="sc">gdb</span> is stopped at a breakpoint in the crate
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‘<samp><span class="samp">K</span></samp>’, then <code>print ::x::y</code> will try to find the symbol
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‘<samp><span class="samp">K::x::y</span></samp>’.
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<p>However, since it is useful to be able to refer to other crates when
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debugging, <span class="sc">gdb</span> provides the <code>extern</code> extension to
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circumvent this. To use the extension, just put <code>extern</code> before
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a path expression to refer to the otherwise unavailable “global”
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scope.
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<p>In the above example, if you wanted to refer to the symbol ‘<samp><span class="samp">y</span></samp>’ in
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the crate ‘<samp><span class="samp">x</span></samp>’, you would use <code>print extern x::y</code>.
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<li>The Rust expression evaluator does not support “statement-like”
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expressions such as <code>if</code> or <code>match</code>, or lambda expressions.
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<li>Tuple expressions are not implemented.
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<li>The Rust expression evaluator does not currently implement the
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<code>Drop</code> trait. Objects that may be created by the evaluator will
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never be destroyed.
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<li><span class="sc">gdb</span> does not implement type inference for generics. In order
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to call generic functions or otherwise refer to generic items, you
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will have to specify the type parameters manually.
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<li><span class="sc">gdb</span> currently uses the C<tt>++</tt> demangler for Rust. In most
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cases this does not cause any problems. However, in an expression
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context, completing a generic function name will give syntactically
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invalid results. This happens because Rust requires the ‘<samp><span class="samp">::</span></samp>’
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operator between the function name and its generic arguments. For
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example, <span class="sc">gdb</span> might provide a completion like
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<code>crate::f<u32></code>, where the parser would require
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<code>crate::f::<u32></code>.
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<li>As of this writing, the Rust compiler (version 1.8) has a few holes in
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the debugging information it generates. These holes prevent certain
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features from being implemented by <span class="sc">gdb</span>:
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<ul>
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<li>Method calls cannot be made via traits.
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<li>Operator overloading is not implemented.
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<li>When debugging in a monomorphized function, you cannot use the generic
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type names.
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<li>The type <code>Self</code> is not available.
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<li><code>use</code> statements are not available, so some names may not be
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available in the crate.
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</ul>
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</ul>
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</body></html>
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