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diff --git a/more/microsoft_vcpp.html b/more/microsoft_vcpp.html new file mode 100644 index 0000000000..822c8b8e94 --- /dev/null +++ b/more/microsoft_vcpp.html @@ -0,0 +1,318 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<title>Portability Hints: Microsoft Visual C++ 6.0 SP4</title> +</head> + +<body bgcolor="#FFFFFF" text="#000000"> + +<table border="1" bgcolor="#007F7F" cellpadding="2"> + <tr> + <td bgcolor="#FFFFFF"><img src="../boost.png" alt="boost.png (6897 bytes)" width="277" height="86"></td> + <td><a href="../index.htm"><font face="Arial,Helvetica" color="#FFFFFF"><big>Home</big></font></a></td> + <td><a href="../libs/libraries.htm"><font face="Arial,Helvetica" color="#FFFFFF"><big>Libraries</big></font></a></td> + <td><a href="../people/people.htm"><font face="Arial,Helvetica" color="#FFFFFF"><big>People</big></font></a></td> + <td><a href="faq.htm"><font face="Arial,Helvetica" color="#FFFFFF"><big>FAQ</big></font></a></td> + <td><a href="index.htm"><font face="Arial,Helvetica" color="#FFFFFF"><big>More</big></font></a></td> + </tr> +</table> + +<p> + +<h1>Portability Hints: Microsoft Visual C++ 6.0 SP4</h1> + +Similar to the +<a href="borland_cpp.html">portability hints for Borland C++</a>, +this page provides hints on some language features of the Microsoft Visual C++ +version 6.0 service pack 4 compiler. A list of +acknowledged deficiencies can be found at the +<a href="http://support.microsoft.com/support/kb/articles/q243/4/51.asp">Microsoft support site</a>. +<p> + +Each entry in the following list describes a particular issue, +complete with sample source code to demonstrate the effect. +Most sample code herein has been verified to compile with gcc 2.95.2 +and Comeau C++ 4.2.44. + + +<h2>Preprocessor symbol</h2> + +The preprocessor symbol <code>_MSC_VER</code> is defined for all +Microsoft C++ compilers. Its value is the internal version number of the +compiler interpreted as a decimal number. Since a few other compilers +also define this symbol, boost provides the symbol +<code>BOOST_MSVC</code>, which is defined in +<a href="../boost/config.hpp">boost/config.hpp</a> +to the value of _MSC_VER if and only if the compiler is really +Microsoft Visual C++. + +The following table lists some known values. +<p> + +<table border="1"> +<tr> +<th>Compiler</th> +<th><code>BOOST_MSVC</code> value</th> +</tr> + +<tr> +<td>Microsoft Visual C++ 6.0 (up to SP4)</td> +<td>1200</td> +</tr> + +</table> + + +<h2>Core Language</h2> + +<h3>[chained using] Chaining <code>using</code>-declarations</h3> + +Chaining <code>using</code>-declarations does not work. +<pre> +void f(); + +namespace N { + using ::f; +} + +void g() +{ + using N::f; // C2873: 'f': the symbol cannot be used in a using-declaration +} +</pre> + + +<h3>[explicit-instantiation] Explicit function template +instantiation</h3> + +Trying to explicitly instantiate a function template leads to the +wrong function being called silently. + +<pre> +#include <stdio.h> + +template<class T> +void f() +{ + printf("%d\n", sizeof(T)); +} + +int main() +{ + f<double>(); // output: "1" + f<char>(); // output: "1" + return 0; +} +</pre> + + +<h3>[for-scoping] Scopes of definitions in for-loops</h3> + +The scope of variable definitions in <code>for</code> loops should be +local to the loop's body, but it is instead local to the enclosing +block. + + +<pre> +int main() +{ + for(int i = 0; i < 5; ++i) + ; + for(int i = 0; i < 5; ++i) // C2374: 'i': Redefinition; multiple initialization + ; + return 0; +} +</pre> + +<strong>Workaround:</strong> Enclose the offending <code>for</code> +loops in another pair of curly braces. +<p> +Another possible workaround (brought to my attention by Vesa Karvonen) +is this: +<pre> +#ifndef for +#define for if (0) {} else for +#endif +</pre> + +Note that platform-specific inline functions in included headers might +depend on the old-style <code>for</code> scoping. + + +<h3>[inclass-member-init] In-class member initialization</h3> + +In-class member initialization, required to implement a +Standard-conforming <code>std::numeric_limits</code> template, does +not work. + +<pre> +struct A +{ + static const int i = 5; // "invalid syntax for pure virtual method" +}; +</pre> + +<strong>Workaround:</strong> Either use an enum (which has incorrect +type, but can be used in compile-time constant expressions), or define +the value out-of-line (which allows for the correct type, but prohibits +using the constant in compile-time constant expressions). See +<a href="int_const_guidelines.htm">Coding Guidelines for Integral Constant Expressions</a> +for guidelines how to define member constants portably in boost +libraries. + + +<h3>[koenig-lookup] Argument-dependent lookup</h3> + +Argument-dependent lookup, also called Koenig lookup, works for +overloaded operators, but not for ordinary functions. No +additional namespaces induced from the argument types seem to be +considered. + +<pre> +namespace N { + struct A {}; + void f(A); +} + +void g() +{ + N::A a; + f(a); // 'f': undeclared identifier +} +</pre> + + +<h3>[template-friend] Templates as friends</h3> + +A Template cannot be declared a friend of a class. + +<pre> +template<class T> +struct A {}; + +struct B +{ + template<class T> + friend struct A; // "syntax error" +}; +</pre> + + +<h3>[member-template-outofline] Out-of-line definitions of member +templates</h3> + +Defining member templates outside their enclosing class does not work. + +<pre> +template<class T> +struct A +{ + template<class U> + void f(); +}; + +template<class T> +template<class U> // "syntax error" +void A<T>::f() // "T: undeclared identifier" +{ +} +</pre> + +<strong>Workaround:</strong> Define member templates in-line within +their enclosing class. + + +<h3>[partial-spec] Partial specialization</h3> + +Partial specialization of class templates does not work. + +<pre> +template<class T> +struct A {}; + +template<class T> +struct B {}; + +template<class T> +struct A<B<T> > {}; // template class was already defined as a non-template +</pre> + +<strong>Workaround:</strong> In some situations where interface +does not matter, class member templates can simulate partial +specialization. + + +<h3>[template-value] Dependent template value parameters</h3> + +Template value parameters whose type depends on a previous template +parameter provoke an internal compiler error if the correct syntax +(with "typename") is used. + +<pre> +template<class T, typename T::result_type> // C1001: INTERNAL COMPILER ERROR: msc1.cpp, line 1794 +struct B {}; + // (omit "typename" and it compiles) + +</pre> + +<strong>Workaround:</strong> Leave off the "typename" keyword. That makes +the program non-conforming, though. + + +<h3>[wchar_t] <code>wchar_t</code> is not built-in</h3> + +The type <code>wchar_t</code> is not a built-in type. + +<pre> +wchar_t x; // "missing storage class or type identifier" +</pre> + +<strong>Workaround:</strong> When using Microsoft Visual C++, the +header +<a href="../boost/config.hpp">boost/config.hpp</a> +includes <code><cstddef></code>, which defines +<code>wchar_t</code> as a typedef for <code>unsigned +short</code>. Note that this means that the compiler does not regard +<code>wchar_t</code> and <code>unsigned short</code> as distinct +types, as is required by the standard, and so ambiguities may emanate +when overloading on <code>wchar_t</code>. The macro +<code>BOOST_NO_INTRINSIC_WCHAR_T</code> is defined in this situation. + + +<h3>[delete-const-pointer] Deleting <code>const X *</code> does not work</h3> + +Trying to delete a pointer to a cv-qualified type gives an error: +<pre> +void f() +{ + const int *p = new int(5); + delete p; // C2664: cannot convert from "const int *" to "void *" +} +</pre> + +<strong>Workaround:</strong> Define the function +<pre> +inline void operator delete(const void *p) throw() +{ operator delete(const_cast<void*>(p)); } +</pre> +and similar functions for the other cv-qualifier combinations, for +operator delete[], and for the <code>std::nothrow</code> variants. + + + +<h2>Standard Library</h2> + +<h3>[clib-namespace] C library names in global namespace instead of std</h3> +<p>Library names from the <c...> headers are in the global namespace +instead of namespace std.<p><b>Workaround:</b> The header <a href="../libs/config/config.htm">boost/config.hpp</a> +will define BOOST_NO_STDC_NAMESPACE. It can be used as follows: +<pre># ifdef BOOST_NO_STDC_NAMESPACE + namespace std { using ::abs; using ::fabs; } +# endif</pre> +<p>Because std::size_t and std::ptrdiff_t are so commonly used, the workaround +for these is already provided in boost/config.hpp.<p> +<hr> + +2001-05-04 <a href="../people/jens_maurer.htm">Jens Maurer</a> +</body> +</html> |