<HTML> <HEAD> <!-- Created by texi2html 1.56k from cln.texi on 2 June 2000 --> <TITLE>CLN, a Class Library for Numbers - 12. Customizing</TITLE> </HEAD> <BODY> 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>. <P><HR><P> <H1><A NAME="SEC69" HREF="cln_toc.html#TOC69">12. Customizing</A></H1> <P> <A NAME="IDX327"></A> <H2><A NAME="SEC70" HREF="cln_toc.html#TOC70">12.1 Error handling</A></H2> <P> When a fatal error occurs, an error message is output to the standard error output stream, and the function <CODE>cl_abort</CODE> is called. The default version of this function (provided in the library) terminates the application. To catch such a fatal error, you need to define the function <CODE>cl_abort</CODE> yourself, with the prototype <PRE> #include <cl_abort.h> void cl_abort (void); </PRE> <P> <A NAME="IDX328"></A> This function must not return control to its caller. <H2><A NAME="SEC71" HREF="cln_toc.html#TOC71">12.2 Floating-point underflow</A></H2> <P> <A NAME="IDX329"></A> <P> Floating point underflow denotes the situation when a floating-point number is to be created which is so close to <CODE>0</CODE> that its exponent is too low to be represented internally. By default, this causes a fatal error. If you set the global variable <PRE> cl_boolean cl_inhibit_floating_point_underflow </PRE> <P> to <CODE>cl_true</CODE>, the error will be inhibited, and a floating-point zero will be generated instead. The default value of <CODE>cl_inhibit_floating_point_underflow</CODE> is <CODE>cl_false</CODE>. <H2><A NAME="SEC72" HREF="cln_toc.html#TOC72">12.3 Customizing I/O</A></H2> <P> The output of the function <CODE>fprint</CODE> may be customized by changing the value of the global variable <CODE>cl_default_print_flags</CODE>. <A NAME="IDX330"></A> <H2><A NAME="SEC73" HREF="cln_toc.html#TOC73">12.4 Customizing the memory allocator</A></H2> <P> Every memory allocation of CLN is done through the function pointer <CODE>cl_malloc_hook</CODE>. Freeing of this memory is done through the function pointer <CODE>cl_free_hook</CODE>. The default versions of these functions, provided in the library, call <CODE>malloc</CODE> and <CODE>free</CODE> and check the <CODE>malloc</CODE> result against <CODE>NULL</CODE>. If you want to provide another memory allocator, you need to define the variables <CODE>cl_malloc_hook</CODE> and <CODE>cl_free_hook</CODE> yourself, like this: <PRE> #include <cl_malloc.h> void* (*cl_malloc_hook) (size_t size) = ...; void (*cl_free_hook) (void* ptr) = ...; </PRE> <P> <A NAME="IDX331"></A> <A NAME="IDX332"></A> The <CODE>cl_malloc_hook</CODE> function must not return a <CODE>NULL</CODE> pointer. <P> It is not possible to change the memory allocator at runtime, because it is already called at program startup by the constructors of some global variables. <P><HR><P> 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>. </BODY> </HTML>