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A well-chosen name helps to unambiguouslydescribe the purpose of the macro. Macros in M4 are all namedwithin a single namespace and, thus, it is necessary to follow aconvention to ensure that names retain uniqueness. This reasoning goesbeyond just avoiding collisions with other macros--if you happen tochoose a name that is already known to M4 as a definition of anykind, your macro's name could be rewritten by the prior definitionduring macro processing.</P><P>One naming convention has emerged--prefixing each macro name with thename of the package that the macro originated in or the initials of themacro's author. Macros are usually named in a hierarchical fashion,with each part of the name separated by underscores. As you moveleft-to-right through each component of the name, the descriptionbecomes more detailed. There are some high-level categories of macrossuggested by the Autoconf manual that you may wish to use when forming adescriptive name for your own macro. For example, if your macro triesto discover the existence of a particular C structure, you might wish touse <CODE>C</CODE> and <CODE>STRUCT</CODE> as components of its name.</P><P><DL COMPACT><DT><SAMP>`C'</SAMP><DD>Tests related to constructs of the C programming language.<DT><SAMP>`DECL'</SAMP><DD>Tests for variable declarations in header files.<DT><SAMP>`FUNC'</SAMP><DD>Tests for functions present in (or absent from) libraries.<DT><SAMP>`HEADER'</SAMP><DD>Tests for header files.<DT><SAMP>`LIB'</SAMP><DD>Tests for libraries.<DT><SAMP>`PATH'</SAMP><DD>Tests to discover absolute filenames (especially programs).<DT><SAMP>`PROG'</SAMP><DD>Tests to determine the base names of programs.<DT><SAMP>`STRUCT'</SAMP><DD>Tests for definitions of C structures in header files.<DT><SAMP>`SYS'</SAMP><DD>Tests for operating system features, such as restartable system calls.<DT><SAMP>`TYPE'</SAMP><DD>Tests for built-in or declared C data types.<DT><SAMP>`VAR'</SAMP><DD>Tests for C variables in libraries.</DL><P>Some examples of macro names formed in this way include:</P><P><DL COMPACT><DT><SAMP>`AC_PROG_CC'</SAMP><DD>A test that looks for a program called <CODE>cc</CODE>.<P><DT><SAMP>`AC_C_INLINE'</SAMP><DD>A test that discovers if the C keyword <CODE>inline</CODE> is recognized.<P><DT><SAMP>`bje_CXX_MUTABLE'</SAMP><DD>A test, written by "bje", that discovers if the C++ keyword<CODE>mutable</CODE> is recognized.</DL><P><A NAME="Macro interface"></A></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Gary V. Vaughan</I> on <I>September, 12 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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