118 lines
6.0 KiB
HTML
118 lines
6.0 KiB
HTML
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<title>Explicit Locations - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Specify-Location.html#Specify-Location" title="Specify Location">
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<link rel="prev" href="Linespec-Locations.html#Linespec-Locations" title="Linespec Locations">
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<link rel="next" href="Address-Locations.html#Address-Locations" title="Address Locations">
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<body>
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<div class="node">
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<a name="Explicit-Locations"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Address-Locations.html#Address-Locations">Address Locations</a>,
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Previous: <a rel="previous" accesskey="p" href="Linespec-Locations.html#Linespec-Locations">Linespec Locations</a>,
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Up: <a rel="up" accesskey="u" href="Specify-Location.html#Specify-Location">Specify Location</a>
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<hr>
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</div>
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<h4 class="subsection">9.2.2 Explicit Locations</h4>
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<p><a name="index-explicit-locations-565"></a>
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<dfn>Explicit locations</dfn> allow the user to directly specify the source
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location's parameters using option-value pairs.
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<p>Explicit locations are useful when several functions, labels, or
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file names have the same name (base name for files) in the program's
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sources. In these cases, explicit locations point to the source
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line you meant more accurately and unambiguously. Also, using
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explicit locations might be faster in large programs.
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<p>For example, the linespec ‘<samp><span class="samp">foo:bar</span></samp>’ may refer to a function <code>bar</code>
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defined in the file named <samp><span class="file">foo</span></samp> or the label <code>bar</code> in a function
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named <code>foo</code>. <span class="sc">gdb</span> must search either the file system or
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the symbol table to know.
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<p>The list of valid explicit location options is summarized in the
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following table:
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<dl>
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<dt><code>-source </code><var>filename</var><dd>The value specifies the source file name. To differentiate between
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files with the same base name, prepend as many directories as is necessary
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to uniquely identify the desired file, e.g., <samp><span class="file">foo/bar/baz.c</span></samp>. Otherwise
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<span class="sc">gdb</span> will use the first file it finds with the given base
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name. This option requires the use of either <code>-function</code> or <code>-line</code>.
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<br><dt><code>-function </code><var>function</var><dd>The value specifies the name of a function. Operations
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on function locations unmodified by other options (such as <code>-label</code>
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or <code>-line</code>) refer to the line that begins the body of the function.
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In C, for example, this is the line with the open brace.
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<p>By default, in C<tt>++</tt> and Ada, <var>function</var> is interpreted as
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specifying all functions named <var>function</var> in all scopes. For
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C<tt>++</tt>, this means in all namespaces and classes. For Ada, this
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means in all packages.
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<p>For example, assuming a program with C<tt>++</tt> symbols named
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<code>A::B::func</code> and <code>B::func</code>, both commands <kbd>break -function func</kbd><!-- /@w --> and <kbd>break -function B::func</kbd><!-- /@w --> set a
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breakpoint on both symbols.
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<p>You can use the <kbd>-qualified</kbd> flag to override this (see below).
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<br><dt><code>-qualified</code><dd>
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This flag makes <span class="sc">gdb</span> interpret a function name specified with
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<kbd>-function</kbd> as a complete fully-qualified name.
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<p>For example, assuming a C<tt>++</tt> program with symbols named
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<code>A::B::func</code> and <code>B::func</code>, the <kbd>break -qualified -function B::func</kbd><!-- /@w --> command sets a breakpoint on <code>B::func</code>, only.
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<p>(Note: the <kbd>-qualified</kbd> option can precede a linespec as well
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(see <a href="Linespec-Locations.html#Linespec-Locations">Linespec Locations</a>), so the particular example above could be
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simplified as <kbd>break -qualified B::func</kbd><!-- /@w -->.)
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<br><dt><code>-label </code><var>label</var><dd>The value specifies the name of a label. When the function
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name is not specified, the label is searched in the function of the currently
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selected stack frame.
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<br><dt><code>-line </code><var>number</var><dd>The value specifies a line offset for the location. The offset may either
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be absolute (<code>-line 3</code>) or relative (<code>-line +3</code>), depending on
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the command. When specified without any other options, the line offset is
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relative to the current line.
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</dl>
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<p>Explicit location options may be abbreviated by omitting any non-unique
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trailing characters from the option name, e.g., <kbd>break -s main.c -li 3</kbd><!-- /@w -->.
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</body></html>
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