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<h3 class="section">4.4 Common Blocks</h3>

<p>A common block is a statically allocated section of memory which can be
referred to by several source files.  It may contain several variables. 
I believe Fortran is the only language with this feature.

   <p><a name="index-N_005fBCOMM-31"></a><a name="index-N_005fECOMM-32"></a><a name="index-C_005fBCOMM-33"></a><a name="index-C_005fECOMM-34"></a>A <code>N_BCOMM</code> stab begins a common block and an <code>N_ECOMM</code> stab
ends it.  The only field that is significant in these two stabs is the
string, which names a normal (non-debugging) symbol that gives the
address of the common block.  According to IBM documentation, only the
<code>N_BCOMM</code> has the name of the common block (even though their
compiler actually puts it both places).

   <p><a name="index-N_005fECOML-35"></a><a name="index-C_005fECOML-36"></a>The stabs for the members of the common block are between the
<code>N_BCOMM</code> and the <code>N_ECOMM</code>; the value of each stab is the
offset within the common block of that variable.  IBM uses the
<code>C_ECOML</code> stab type, and there is a corresponding <code>N_ECOML</code>
stab type, but Sun's Fortran compiler uses <code>N_GSYM</code> instead.  The
variables within a common block use the &lsquo;<samp><span class="samp">V</span></samp>&rsquo; symbol descriptor (I
believe this is true of all Fortran variables).  Other stabs (at least
type declarations using <code>C_DECL</code>) can also be between the
<code>N_BCOMM</code> and the <code>N_ECOMM</code>.

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