462b73969e
2001-05-30 Phil Edwards <pme@sources.redhat.com> * docs/doxygen/user.cfg.in: Minor addition. * docs/html/documentation.html: Reorganize. Put most-looked-at stuff first. * docs/html/install.html: Update for 3.0. HTML fixups. * docs/html/17_intro/howto.html: Likewise. * docs/html/18_support/howto.html: Likewise. * docs/html/19_diagnostics/howto.html: Likewise. * docs/html/20_util/howto.html: Likewise. * docs/html/23_containers/howto.html: Likewise. * docs/html/24_iterators/howto.html: Likewise. More notes. * docs/html/25_algorithms/howto.html: Likewise. * docs/html/26_numerics/howto.html: Likewise. More notes. * docs/html/27_io/howto.html: Likewise. * docs/html/ext/howto.html: Likewise. * docs/html/faq/index.html: Likewise. * docs/html/faq/index.txt: Regenerate. * docs/html/27_io/iostreams_hierarchy.pdf: Remove in favor of Doxygen-created documentation. From-SVN: r42723
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117 lines
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HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
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<HTML>
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<HEAD>
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
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<META NAME="AUTHOR" CONTENT="pme@sources.redhat.com (Phil Edwards)">
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<META NAME="KEYWORDS" CONTENT="HOWTO, libstdc++, GCC, g++, libg++, STL">
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<META NAME="DESCRIPTION" CONTENT="HOWTO for the libstdc++ chapter 19.">
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<META NAME="GENERATOR" CONTENT="vi and eight fingers">
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<TITLE>libstdc++-v3 HOWTO: Chapter 19</TITLE>
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<LINK REL=StyleSheet HREF="../lib3styles.css">
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<!-- $Id: howto.html,v 1.3 2001/04/03 00:26:55 pme Exp $ -->
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</HEAD>
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<BODY>
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<H1 CLASS="centered"><A NAME="top">Chapter 19: Diagnostics</A></H1>
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<P>Chapter 19 deals with program diagnostics, such as exceptions
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and assertions. You know, all the things we wish weren't even
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necessary at all.
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</P>
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<!-- ####################################################### -->
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<HR>
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<H1>Contents</H1>
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<UL>
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<LI><A HREF="#1">Adding data to exceptions</A>
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<LI><A HREF="#2">Exception class hierarchy diagram</A>
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<LI><A HREF="#3">Concept checkers -- <STRONG>new and improved!</STRONG></A>
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</UL>
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<HR>
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<H2><A NAME="1">Adding data to exceptions</A></H2>
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<P>The standard exception classes carry with them a single string as
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data (usually describing what went wrong or where the 'throw' took
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place). It's good to remember that you can add your own data to
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these exceptions when extending the heirarchy:
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</P>
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<PRE>
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using std::runtime_error;
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struct My_Exception : public runtime_error
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{
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public:
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My_Exception (const string& whatarg)
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: runtime_error(whatarg), e(errno), id(GetDataBaseID()) { }
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int errno_at_time_of_throw() const { return e; }
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DBID id_of_thing_that_threw() const { return id; }
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protected:
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int e;
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DBID id; // some user-defined type
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};
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</PRE>
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<P>Return <A HREF="#top">to top of page</A> or
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<A HREF="../faq/index.html">to the FAQ</A>.
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</P>
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<HR>
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<H2><A NAME="2">Exception class hierarchy diagram</A></H2>
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<P>The <A HREF="exceptions_hiearchy.pdf">diagram</A> is in PDF, or
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at least it will be once it gets finished.
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</P>
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<P>Return <A HREF="#top">to top of page</A> or
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<A HREF="../faq/index.html">to the FAQ</A>.
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</P>
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<HR>
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<H2><A NAME="3">Concept checkers -- <STRONG>new and improved!</STRONG></A></H2>
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<P>Better taste! Less fat! Literally!</P>
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<P>In 1999, SGI added <EM>concept checkers</EM> to their implementation
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of the STL: code which checked the template parameters of
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instantiated pieces of the STL, in order to insure that the parameters
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being used met the requirements of the standard. For example,
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the Standard requires that types passed as template parameters to
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<TT>vector</TT> be "Assignable" (which means what you think
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it means). The checking was done during compilation, and none of
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the code was executed at runtime.
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</P>
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<P>Unfortunately, the size of the compiler files grew significantly
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as a result. The checking code itself was cumbersome. And bugs
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were found in it on more than one occasion.
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</P>
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<P>The primary author of the checking code, Jeremy Siek, had already
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started work on a replcement implementation. The new code has been
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formally reviewed and accepted into
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<A HREF="http://www.boost.org/libs/concept_check/concept_check.htm">the
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Boost libraries</A>, and we are pleased to incorporate it into the
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GNU C++ library.
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</P>
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<P>The new version imposes a much smaller space overhead on the generated
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object file. The checks are also cleaner and easier to read and
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understand.
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</P>
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<P>Right now they are off by default. More will be added once
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GCC 3.0 is released and we have time to revisit this topic.
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</P>
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<P>Return <A HREF="#top">to top of page</A> or
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<A HREF="../faq/index.html">to the FAQ</A>.
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</P>
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<!-- ####################################################### -->
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<HR>
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<P CLASS="fineprint"><EM>
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Comments and suggestions are welcome, and may be sent to
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<A HREF="mailto:libstdc++@gcc.gnu.org">the mailing list</A>.
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<BR> $Id: howto.html,v 1.3 2001/04/03 00:26:55 pme Exp $
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</EM></P>
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</BODY>
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</HTML>
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