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| 2 | <head> |
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| 3 | <title>libsm : C Language Portability Macros</title> |
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| 4 | </head> |
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| 5 | <body> |
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| 6 | |
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| 7 | <a href="index.html">Back to libsm overview</a> |
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| 8 | |
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| 9 | <center> |
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| 10 | <h1> libsm : C Language Portability Macros </h1> |
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| 11 | <br> $Id: cdefs.html,v 1.1.1.1 2003-04-08 15:11:42 zacheiss Exp $ |
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| 12 | </center> |
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| 13 | |
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| 14 | <h2> Description </h2> |
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| 15 | |
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| 16 | The header file <tt><sm/cdefs.h></tt> |
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| 17 | defines portable interfaces to non-portable features |
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| 18 | of various C compilers. |
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| 19 | It also assists you in writing C header files that are compatible |
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| 20 | with C++. |
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| 21 | |
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| 22 | <dl> |
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| 23 | <dt> |
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| 24 | <tt> __P(parameterlist) </tt> |
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| 25 | <dd> |
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| 26 | This macro is used to write portable function prototypes. |
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| 27 | For example, |
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| 28 | |
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| 29 | <blockquote><pre> |
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| 30 | int foo __P((int)); |
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| 31 | </pre></blockquote> |
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| 32 | |
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| 33 | <dt> |
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| 34 | <tt> __CONCAT(x,y) </tt> |
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| 35 | <dd> |
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| 36 | This macro concatenates two tokens x and y, |
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| 37 | forming a single token xy. |
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| 38 | Warning: make sure there is no white space around the arguments x and y. |
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| 39 | <p> |
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| 40 | |
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| 41 | <dt> |
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| 42 | <tt> __STRING(x) </tt> |
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| 43 | <dd> |
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| 44 | This macro converts the token sequence x into a string literal. |
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| 45 | <p> |
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| 46 | |
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| 47 | <dt> |
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| 48 | <tt> __BEGIN_DECLS, __END_DECLS </tt> |
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| 49 | <dd> |
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| 50 | These macros are used to write C header files that are compatible |
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| 51 | with C++ compilers. |
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| 52 | Put <tt>__BEGIN_DECLS</tt> before the first function or variable |
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| 53 | declaration in your header file, |
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| 54 | and put <tt>__END_DECLS</tt> after the last function or variable |
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| 55 | declaration. |
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| 56 | <p> |
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| 57 | |
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| 58 | <dt> |
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| 59 | <tt> const, signed, volatile </tt> |
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| 60 | <dd> |
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| 61 | For pre-ANSI C compilers, <tt>const</tt>, <tt>signed</tt> |
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| 62 | and <tt>volatile</tt> are defined as empty macros. |
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| 63 | This means you can use these keywords without introducing |
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| 64 | portability problems. |
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| 65 | <p> |
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| 66 | |
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| 67 | <dt> |
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| 68 | <tt> SM_DEAD(function_declaration) </tt> |
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| 69 | <dd> |
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| 70 | This macro modifies a prototype of a function |
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| 71 | that does not return to its caller. |
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| 72 | With some versions of gcc, this will result in slightly better code, |
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| 73 | and can suppress some useless warnings produced by gcc -Wall. |
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| 74 | For example, |
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| 75 | |
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| 76 | <blockquote><pre> |
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| 77 | SM_DEAD(void exit __P((int))); |
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| 78 | </pre></blockquote> |
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| 79 | |
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| 80 | <dt> |
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| 81 | <tt> SM_UNUSED(variable_declaration) </tt> |
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| 82 | <dd> |
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| 83 | This macro modifies a definition of an unused |
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| 84 | local variable, global variable or function parameter |
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| 85 | in order to suppress compiler warnings. |
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| 86 | Examples: |
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| 87 | |
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| 88 | <blockquote><pre> |
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| 89 | SM_UNUSED(static const char Id[]) = "@(#)$Id: cdefs.html,v 1.1.1.1 2003-04-08 15:11:42 zacheiss Exp $"; |
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| 90 | void |
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| 91 | foo(x) |
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| 92 | SM_UNUSED(int x); |
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| 93 | { |
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| 94 | SM_UNUSED(int y) = 0; |
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| 95 | return 0; |
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| 96 | } |
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| 97 | void |
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| 98 | bar(SM_UNUSED(int x)) |
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| 99 | { |
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| 100 | return 0; |
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| 101 | } |
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| 102 | </pre></blockquote> |
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| 103 | |
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| 104 | </dl> |
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| 105 | |
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| 106 | </body> |
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| 107 | </html> |
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