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132 lines
9 KiB
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<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>STLport: Note for IBM OS/390 C/C++ Users</title><link href="doc.css" type="text/css" rel="stylesheet"></head><body marginwidth="0" marginheight="0" leftmargin="0" topmargin="0" vlink="#314A30" link="#314A30" text="black" bgcolor="white"><table border="0" cellspacing="0" cellpadding="0"><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img border="0" height="14" width="1" src="images/trans.gif"><br><a href="../index.html"><img src="images/stl_logo_doc.gif" border="0" height="80" width="80"></a><a href="http://www.stlport.com"><img border="0" height="80" width="461" src="images/t_doc2.gif"></a><br><img src="images/trans.gif" border="0" height="24" width="1"><br><img src="images/black.gif" border="0" height="1" width="776"><br><img src="images/trans.gif" border="0" height="24" width="1"></td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img src="images/trans.gif" border="0" height="10" width="776"></td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776">
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<span class="heading">Note for IBM OS/390 C/C++ Users</span>
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<p> </p>
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<hr>
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<br>
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<b><i><font face="Arial,Helvetica,Geneva"><font size="+1">Known Problems</font></font></i></b>
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<p><b>Compiling:</b></p>
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<ol>
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<li>OS/390 C/C++ requires explicit template notation such as
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template_class<Param> where most other conformant compilers
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only accept template_class (inside template method bodies, etc.):</li>
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<p><br>
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<br>
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<font size="+0"> template <class Param> class
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template_class {<br>
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<br>
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template_class foo();
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// error for OS390 C/C++<br>
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<br>
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template_class<Param> foo();
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// OK<br>
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<br>
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...<br>
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<br>
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};</font></p>
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This adaptation works around the above OS/390 C/C++ requirement, but
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may cause compatibility problems when porting template code from other
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platforms.
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<li>OS/390 C++, does not allow passing an extern "C"
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function pointer as an argument to a C++ function. For example:</li>
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<p><br>
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<br>
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<font size="+0"> template <class Result> <br>
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<br>
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pointer_to_void_function<Result>
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ptr_gen(Result (*x)());<br>
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<br>
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<br>
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<br>
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p = ptr_gen(rand); // error for OS/390 C/C++</font></p>
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In the above template, <i>ptr_gen</i> takes a function pointer as its
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argument and returns a function pointer adaptor (a type of function
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object), and <i>rand</i> is an extern "C" library pointer.
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This is not allowed because C and C++ linkage is different on OS/390
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C/C++.
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<p>To work around this problem, provide a C++ wrapper around the
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extern "C" function and pass the C++ wrapper instead:</p>
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<p><br>
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<br>
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<font size="+0"> int cxxrand(void) { return rand();}<br>
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<br>
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p = ptr_gen(cxxrand);
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// OK</font></p>
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<li>OS/390 C++ does not allow functions to be declared with a function
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or an array as its return type:</li>
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<p><br>
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<br>
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<font size="+0"> template <class InputIterator, class
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OutputIterator,class result)<br>
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<br>
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OutputIterator
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adjacent_difference(InputIterator first, <br>
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<br>
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InputIterator
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last, <br>
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<br>
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OutputIterator
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result);<br>
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<br>
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<br>
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<br>
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main() {<br>
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<br>
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int number[10];<br>
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<br>
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int different[5];<br>
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<br>
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adjacent_difference(number,<br>
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<br>
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number
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+ 5,<br>
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<br>
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different);
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// error for OS/390 C/C++<br>
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<br>
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}</font></p>
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In the above example, the compiler attempts to create an instantiation
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that returns an array <i>int[]</i>, which is not allowed in OS/390
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C/C++:
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<p><br>
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<br>
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<font size="+0"> int[] adjacent_difference(int*, int*, int*)</font></p>
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To work around this problem, cast the <i>int</i> array to pointer to <i>int</i>:
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<p><br>
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<br>
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<font size="+0"> adjacent_difference(number,number + 5, (int *)
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different); // OK</font></p>
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</ol>
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<b>Linking:</b>
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<p>Repository handling in the compiler is imperfect, so you may
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experience various problems during the link step. The problems are
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generally of two kinds: duplicate symbols or unresolved symbols. The
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duplicate symbol problem is not fatal, since the symbols are weak
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(compiler generated) in that case. When it comes to large projects,
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however, it may cause unacceptable code bloat (extra code generated by
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the compiler when it separates the template instantiation files into the
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TEMPINC directory). To overcome this problem, this adaptation simulates <i>separate
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template implementation</i>. Compiling templates using the tempinc
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compile option, minimizes code bloat as there are less duplicate
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symbols. The problem with undefined symbols is also caused by imperfect
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repository handling, but may require manual intervention. The general
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rule is: <b>if you get <i>unresolved symbol</i> errors, explicit
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instantiation will most likely help</b>. For example:</p>
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<p><i>Unresolved:</i></p>
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<p><br>
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<br>
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<font size="+0"> __default_alloc_template<0,0>::allocate(unsigned
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long)<br>
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<br>
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__default_alloc_template<0,0>::deallocate(void *, unsigned
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long)</font></p>
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To work around this problem, just instantiate __default_alloc_template<0,0>
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explicitly in a module:
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<p><br>
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<br>
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<font size="+0"> template class __default_alloc_template<0,0>;</font></p>
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<h2><font size="+0">Useful Links</font></h2>
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<p><font size="+0">Check out :</font></p>
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<p><a href="http://www.software.ibm.com/ad/c390/cmvsstlp.htm">http://www.software.ibm.com/ad/c390/cmvsstlp.htm</a></p>
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</td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img src="images/trans.gif" border="0" height="20" width="50"><br><a href="index.html">Table of Contents</a><br></td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img src="images/trans.gif" border="0" height="40" width="80"><br><img src="images/black.gif" border="0" height="1" width="776"></td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img src="images/black.gif" border="0" height="1" width="776"></td></tr><tr valign="top" align="left"><td width="24"><img src="images/trans.gif" border="0" height="1" width="24"></td><td width="776"><img src="images/trans.gif" border="0" height="5" width="50"><br><span class="copyright">Copyright 2001 by STLport</span><br><img src="images/trans.gif" border="0" height="50" width="80"></td></tr></table></body></html>
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