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97 lines
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97 lines
3.0 KiB
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<!-- Created by texi2html 1.56k from cln.texi on 14 January 2000 -->
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<TITLE>CLN, a Class Library for Numbers - 12. Customizing</TITLE>
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Go to the <A HREF="cln_1.html">first</A>, <A HREF="cln_11.html">previous</A>, <A HREF="cln_13.html">next</A>, <A HREF="cln_13.html">last</A> section, <A HREF="cln_toc.html">table of contents</A>.
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<P><HR><P>
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<H1><A NAME="SEC68" HREF="cln_toc.html#TOC68">12. Customizing</A></H1>
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<H2><A NAME="SEC69" HREF="cln_toc.html#TOC69">12.1 Error handling</A></H2>
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<P>
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When a fatal error occurs, an error message is output to the standard error
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output stream, and the function <CODE>cl_abort</CODE> is called. The default
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version of this function (provided in the library) terminates the application.
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To catch such a fatal error, you need to define the function <CODE>cl_abort</CODE>
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yourself, with the prototype
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<PRE>
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#include <cl_abort.h>
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void cl_abort (void);
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</PRE>
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<P>
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This function must not return control to its caller.
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<H2><A NAME="SEC70" HREF="cln_toc.html#TOC70">12.2 Floating-point underflow</A></H2>
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<P>
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Floating point underflow denotes the situation when a floating-point number
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is to be created which is so close to <CODE>0</CODE> that its exponent is too
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low to be represented internally. By default, this causes a fatal error.
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If you set the global variable
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<PRE>
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cl_boolean cl_inhibit_floating_point_underflow
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</PRE>
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<P>
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to <CODE>cl_true</CODE>, the error will be inhibited, and a floating-point zero
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will be generated instead.
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The default value of <CODE>cl_inhibit_floating_point_underflow</CODE> is
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<CODE>cl_false</CODE>.
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<H2><A NAME="SEC71" HREF="cln_toc.html#TOC71">12.3 Customizing I/O</A></H2>
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<P>
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The output of the function <CODE>fprint</CODE> may be customized by changing the
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value of the global variable <CODE>cl_default_print_flags</CODE>.
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<H2><A NAME="SEC72" HREF="cln_toc.html#TOC72">12.4 Customizing the memory allocator</A></H2>
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<P>
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Every memory allocation of CLN is done through the function pointer
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<CODE>cl_malloc_hook</CODE>. Freeing of this memory is done through the function
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pointer <CODE>cl_free_hook</CODE>. The default versions of these functions,
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provided in the library, call <CODE>malloc</CODE> and <CODE>free</CODE> and check
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the <CODE>malloc</CODE> result against <CODE>NULL</CODE>.
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If you want to provide another memory allocator, you need to define
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the variables <CODE>cl_malloc_hook</CODE> and <CODE>cl_free_hook</CODE> yourself,
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like this:
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<PRE>
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#include <cl_malloc.h>
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void* (*cl_malloc_hook) (size_t size) = ...;
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void (*cl_free_hook) (void* ptr) = ...;
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</PRE>
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<P>
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The <CODE>cl_malloc_hook</CODE> function must not return a <CODE>NULL</CODE> pointer.
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<P>
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It is not possible to change the memory allocator at runtime, because
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it is already called at program startup by the constructors of some
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global variables.
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<P><HR><P>
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Go to the <A HREF="cln_1.html">first</A>, <A HREF="cln_11.html">previous</A>, <A HREF="cln_13.html">next</A>, <A HREF="cln_13.html">last</A> section, <A HREF="cln_toc.html">table of contents</A>.
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