2001-11-25 18:32:11 +00:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML><HEAD><TITLE>Boost PREPROCESSOR library</TITLE>
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<BODY bgcolor="#ffffff">
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<a href="index.htm"><IMG height=86
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alt="c++boost.gif (8819 bytes)"
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src="../../../c++boost.gif"
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width=277 align=center></a>
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<hr>
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<h1>Boost PREPROCESSOR library: Known problems with specific compilers</h1>
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<p> Some compilers have buggy or limited preprocessors. This page explains known
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problems with specific compilers.</p>
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<hr>
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<h2>Contents</h2>
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<ul>
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<li><a href="#Metrowerks Codewarrior 7.0">Metrowerks Codewarrior 7.0</a></li>
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2001-11-27 04:30:22 +00:00
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<li><a href="#Comeau C/C++ 4.2.45.2">Comeau C/C++ 4.2.45.2 for Windows</a></li>
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2001-11-25 18:32:11 +00:00
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</ul>
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<HR>
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2001-11-27 04:30:22 +00:00
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2001-11-25 18:32:11 +00:00
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<h3><a name="Metrowerks Codewarrior 7.0">Metrowerks Codewarrior 7.0</a></h3>
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2001-11-27 04:30:22 +00:00
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<p>Metrowerks Codewarrior 7.0 has a bug in preprocessor (to be more
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2001-11-25 18:32:11 +00:00
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concrete, in function-like macro replacement mechanism) that restricts usage
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of the library to only very simple cases, at least if you don't write code that
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specifically address this issue; for example, the above NUMBERED_EXPRESSION
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example doesn't compile on CW 7.0. Below is a simple test case that reproduces
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the bug:</p>
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<blockquote>
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<pre>#define IDENTITY_MACRO(x) IDENTITY_MACRO_BODY(x)
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#define IDENTITY_MACRO_BODY(x) x
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#define COMMA_TOKEN() ,
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int a IDENTITY_MACRO(COMMA_TOKEN)() b; // this works
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int c IDENTITY_MACRO(IDENTITY_MACRO(COMMA_TOKEN))() d; // this doesn't
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</pre>
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</blockquote>
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<p>Basically, what's happening here is that function-like COMMA_TOKEN macro gets
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expanded _inside_ of the nested IDENTITY_MACRO call - even although it's NOT
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followed by a '(' as the next preprocessing token - which is a clearly an incorrect
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behavior (see 16.3 [cpp.replace] para 9 for the detailed description of the
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2001-11-27 04:30:22 +00:00
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function-like macro replacement process). I've submitted a bug report, but they
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haven't confirmed it yet.</p>
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2001-11-25 18:32:11 +00:00
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<p>So, this is not a problem of the library, but probably something that needs
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to be mentioned in the documentation, may be with some examples of how to workaround
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the issue. Just to show one possible way around the problem, here is a NUMBERED_EXPRESSION
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macro that does work on MWCW:</p>
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<blockquote>
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<pre>#define NUMBERED_EXPRESSION(n, x) \
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BOOST_PREPROCESSOR_CAT(BOOST_, \
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BOOST_PREPROCESSOR_IF( \
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n \
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, PREPROCESSOR_IDENTITY(x##n) \
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, PREPROCESSOR_EMPTY \
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))() \
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/**/
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</pre></blockquote>
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<p align="right"><i>Reported by Aleksey Gurtovoy</i></p>
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2001-11-27 04:30:22 +00:00
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<h3><a name="Comeau C/C++ 4.2.45.2">Comeau C/C++ 4.2.45.2 for Windows</a></h3>
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<p>It appears that their algorithm of macro call invocation is quite far
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from ideal, because for the following code fragment (which is a part of
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<a href="../test/preprocessor_test.cpp">preprocessor_test.cpp</a>), the
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linear increasing of IS_FUNCTION_HELPER_TEST_MAX value leads to not even
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quadratic, but something like exponential increasing of compilation time!
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(see the timing data below). This behavior may or may not be problematic
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for you, depending on how intense is your usage of the library.
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<blockquote>
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<pre>#ifndef IS_FUNCTION_HELPER_TEST_MAX
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#define IS_FUNCTION_HELPER_TEST_MAX 40
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#endif
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typedef char yes_type;
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#define IS_FUNCTION_HELPER(I,A)\
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template\
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<BOOST_PREPROCESSOR_ENUM_PARAMS(BOOST_PREPROCESSOR_INC(I),class P)>\
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yes_type is_function_helper(\
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P0 (*)(BOOST_PREPROCESSOR_ENUM_SHIFTED_PARAMS(BOOST_PREPROCESSOR_INC(I),P)));
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BOOST_PREPROCESSOR_REPEAT_2ND(BOOST_PREPROCESSOR_INC(IS_FUNCTION_HELPER_TEST_MAX),IS_FUNCTION_HELPER,A)
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#undef IS_FUNCTION_HELPER
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</pre></blockquote>
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<h4>Timing data:</h4>
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<table border="1">
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<tr align="center">
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<th> </th>
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<th>Comeau C/C++ 4.2.45.2</th>
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<th>Microsoft Visual C++ 6.0 SP5</th>
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</tr>
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<tr align="center">
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<td>10 parameters</td>
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<td><font color="red">< 1 sec</font></td>
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<td>< 1 sec</td>
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</tr>
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<tr align="center">
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<td>20 parameters</td>
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<td><font color="red">~ 2 sec</font></td>
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<td>< 1 sec</td>
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</tr>
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<tr align="center">
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<td>30 parameters</td>
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<td><font color="red">~ 15 sec</font></td>
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<td>< 1 sec</td>
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</tr>
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<tr align="center">
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<td>40 parameters</td>
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<td><font color="red">~ 50 sec</font></td>
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<td>< 1 sec</td>
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</tr>
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</table>
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<p align="right"><i>Reported by Aleksey Gurtovoy</i></p>
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2001-11-25 18:32:11 +00:00
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<hr>
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<P><EFBFBD> Copyright Housemarque, Inc. 2001</P>
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<p>Permission to copy, use, modify, sell and distribute this document is granted
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provided this copyright notice appears in all copies. This document is provided
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"as is" without express or implied warranty, and with no claim as to its suitability
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for any purpose. </p>
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<p>Updated: <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %b %Y" startspan --><!--webbot bot="Timestamp" endspan i-checksum="15246" --></p>
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<p></p>
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