77 lines
3.9 KiB
HTML
77 lines
3.9 KiB
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<title>Questions - STABS</title>
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<meta name="description" content="STABS">
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<link rel="next" href="Stab-Sections.html#Stab-Sections" title="Stab Sections">
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<!--
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Copyright (C) 1992-2019 Free Software Foundation, Inc.
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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and David MacKenzie.
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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, with no Front-Cover Texts, and with no Back-Cover
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Free Documentation License''.-->
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<a name="Questions"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Stab-Sections.html#Stab-Sections">Stab Sections</a>,
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Previous: <a rel="previous" accesskey="p" href="Expanded-Reference.html#Expanded-Reference">Expanded Reference</a>,
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Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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<hr>
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</div>
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<h2 class="appendix">Appendix E Questions and Anomalies</h2>
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<ul>
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<li><!-- I think this is changed in GCC 2.4.5 to put the line number there. -->
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For GNU C stabs defining local and global variables (<code>N_LSYM</code> and
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<code>N_GSYM</code>), the desc field is supposed to contain the source
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line number on which the variable is defined. In reality the desc
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field is always 0. (This behavior is defined in <samp><span class="file">dbxout.c</span></samp> and
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putting a line number in desc is controlled by ‘<samp><span class="samp">#ifdef
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WINNING_GDB</span></samp>’, which defaults to false). GDB supposedly uses this
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information if you say ‘<samp><span class="samp">list </span><var>var</var></samp>’. In reality, <var>var</var> can
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be a variable defined in the program and GDB says ‘<samp><span class="samp">function
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</span><var>var</var><span class="samp"> not defined</span></samp>’.
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<li>In GNU C stabs, there seems to be no way to differentiate tag types:
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structures, unions, and enums (symbol descriptor ‘<samp><span class="samp">T</span></samp>’) and typedefs
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(symbol descriptor ‘<samp><span class="samp">t</span></samp>’) defined at file scope from types defined locally
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to a procedure or other more local scope. They all use the <code>N_LSYM</code>
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stab type. Types defined at procedure scope are emitted after the
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<code>N_RBRAC</code> of the preceding function and before the code of the
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procedure in which they are defined. This is exactly the same as
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types defined in the source file between the two procedure bodies.
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GDB over-compensates by placing all types in block #1, the block for
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symbols of file scope. This is true for default, ‘<samp><span class="samp">-ansi</span></samp>’ and
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‘<samp><span class="samp">-traditional</span></samp>’ compiler options. (Bugs gcc/1063, gdb/1066.)
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<li>What ends the procedure scope? Is it the proc block's <code>N_RBRAC</code> or the
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next <code>N_FUN</code>? (I believe its the first.)
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</ul>
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</body></html>
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