mingw/info/stabs/Common-Blocks.html

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  19 <h3 class="section">Common Blocks</h3>
  20
  21    <p>A common block is a statically allocated section of memory which can be
  22 referred to by several source files.  It may contain several variables.
  23 I believe Fortran is the only language with this feature.
  24
  25    <p>A <code>N_BCOMM</code> stab begins a common block and an <code>N_ECOMM</code> stab
  26 ends it.  The only field that is significant in these two stabs is the
  27 string, which names a normal (non-debugging) symbol that gives the
  28 address of the common block.  According to IBM documentation, only the
  29 <code>N_BCOMM</code> has the name of the common block (even though their
  30 compiler actually puts it both places).
  31
  32    <p>The stabs for the members of the common block are between the
  33 <code>N_BCOMM</code> and the <code>N_ECOMM</code>; the value of each stab is the
  34 offset within the common block of that variable.  IBM uses the
  35 <code>C_ECOML</code> stab type, and there is a corresponding <code>N_ECOML</code>
  36 stab type, but Sun's Fortran compiler uses <code>N_GSYM</code> instead.  The
  37 variables within a common block use the <code>V</code> symbol descriptor (I
  38 believe this is true of all Fortran variables).  Other stabs (at least
  39 type declarations using <code>C_DECL</code>) can also be between the
  40 <code>N_BCOMM</code> and the <code>N_ECOMM</code>.
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