91 lines
4.7 KiB
HTML
91 lines
4.7 KiB
HTML
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<title>Compilation - Debugging with GDB</title>
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<a name="Compilation"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Starting.html#Starting">Starting</a>,
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Up: <a rel="up" accesskey="u" href="Running.html#Running">Running</a>
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<h3 class="section">4.1 Compiling for Debugging</h3>
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<p>In order to debug a program effectively, you need to generate
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debugging information when you compile it. This debugging information
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is stored in the object file; it describes the data type of each
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variable or function and the correspondence between source line numbers
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and addresses in the executable code.
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<p>To request debugging information, specify the ‘<samp><span class="samp">-g</span></samp>’ option when you run
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the compiler.
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<p>Programs that are to be shipped to your customers are compiled with
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optimizations, using the ‘<samp><span class="samp">-O</span></samp>’ compiler option. However, some
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compilers are unable to handle the ‘<samp><span class="samp">-g</span></samp>’ and ‘<samp><span class="samp">-O</span></samp>’ options
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together. Using those compilers, you cannot generate optimized
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executables containing debugging information.
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<p><span class="sc">gcc</span>, the <span class="sc">gnu</span> C/C<tt>++</tt> compiler, supports ‘<samp><span class="samp">-g</span></samp>’ with or
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without ‘<samp><span class="samp">-O</span></samp>’, making it possible to debug optimized code. We
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recommend that you <em>always</em> use ‘<samp><span class="samp">-g</span></samp>’ whenever you compile a
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program. You may think your program is correct, but there is no sense
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in pushing your luck. For more information, see <a href="Optimized-Code.html#Optimized-Code">Optimized Code</a>.
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<p>Older versions of the <span class="sc">gnu</span> C compiler permitted a variant option
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‘<samp><span class="samp">-gg</span></samp>’<!-- /@w --> for debugging information. <span class="sc">gdb</span> no longer supports this
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format; if your <span class="sc">gnu</span> C compiler has this option, do not use it.
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<p><span class="sc">gdb</span> knows about preprocessor macros and can show you their
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expansion (see <a href="Macros.html#Macros">Macros</a>). Most compilers do not include information
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about preprocessor macros in the debugging information if you specify
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the <samp><span class="option">-g</span></samp> flag alone. Version 3.1 and later of <span class="sc">gcc</span>,
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the <span class="sc">gnu</span> C compiler, provides macro information if you are using
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the DWARF debugging format, and specify the option <samp><span class="option">-g3</span></samp>.
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<p>See <a href="../gcc/Debugging-Options.html#Debugging-Options">Options for Debugging Your Program or GCC</a>, for more
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information on <span class="sc">gcc</span> options affecting debug information.
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<p>You will have the best debugging experience if you use the latest
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version of the DWARF debugging format that your compiler supports.
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DWARF is currently the most expressive and best supported debugging
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format in <span class="sc">gdb</span>.
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</body></html>
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