mingw/info/stabs/Register-Variables.html

   1 <html lang="en">
   2 <head>
   3 <title>STABS</title>
   4 <meta http-equiv="Content-Type" content="text/html">
   5 <meta name="description" content="STABS">
   6 <meta name="generator" content="makeinfo 4.3">
   7 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home">
   8 </head>
   9 <body>
  10 <div class="node">
  11 <p>
  12 Node:<a name="Register%20Variables">Register Variables</a>,
  13 Next:<a rel="next" accesskey="n" href="Common-Blocks.html#Common%20Blocks">Common Blocks</a>,
  14 Previous:<a rel="previous" accesskey="p" href="Global-Variables.html#Global%20Variables">Global Variables</a>,
  15 Up:<a rel="up" accesskey="u" href="Variables.html#Variables">Variables</a>
  16 <hr><br>
  17 </div>
  18
  19 <h3 class="section">Register Variables</h3>
  20
  21    <p>Register variables have their own stab type, <code>N_RSYM</code>
  22 (<code>C_RSYM</code> for XCOFF), and their own symbol descriptor, <code>r</code>.
  23 The stab's value is the number of the register where the variable data
  24 will be stored.
  25
  26    <p>AIX defines a separate symbol descriptor <code>d</code> for floating point
  27 registers.  This seems unnecessary; why not just just give floating
  28 point registers different register numbers?  I have not verified whether
  29 the compiler actually uses <code>d</code>.
  30
  31    <p>If the register is explicitly allocated to a global variable, but not
  32 initialized, as in:
  33
  34 <pre class="example">     register int g_bar asm ("%g5");
  35      </pre>
  36
  37 <p>then the stab may be emitted at the end of the object file, with
  38 the other bss symbols.
  39
  40    </body></html>
  41