有关宏和外部函数的基础问题

goodluck16 2008-03-03 09:34:48
本人刚学C++,遇到以下代码:
在头文件中声明:

#ifdef HAVE_PROTOTYPES
#define JPP(arglist) arglist
#else
#define JPP(arglist) ()
#endif

EXTERN(boolean) keymatch JPP((char * arg, const char * keyword, int minchars));
EXTERN(FILE *) read_stdin JPP((void));


不清楚其含义.这是在声明外部函数么?在那个外部函数的所在的模块中,其函数名字应该是什么?
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bicener 2008-03-03
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  属于条件编译,自我感觉现在C++用的不多了,多用于MFC中。
  个人认为意思是
     如果定义了HAVE_PROTOTYPES ,则JPP(arglist)用arglist替代,如果没有则用另一个替代
int2e 2008-03-03
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参数列表的过滤宏
有什么疑问?
Chappell 2008-03-03
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up
babyvox1999 2008-03-03
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根据宏来达到改变函数参数的目的
The C programming Language 第二版英文版 內容列表 Table of Contents Preface.......................................................... Preface to the first edition..................................... Introduction..................................................... Chapter 1 - A Tutorial Introduction.............................. 1.1 Getting Started................................ 1.2 Variables and Arithmetic Expressions........... 1.3 The for statement.............................. 1.4 Symbolic Constants............................. 1.5 Character Input and Output..................... 1.5.1 File Copying.......................... 1.5.2 Character Counting.................... 1.5.3 Line Counting......................... 1.5.4 Word Counting......................... 1.6 Arrays......................................... 1.7 Functions...................................... 1.8 Arguments - Call by Value...................... 1.9 Character Arrays............................... 1.10 External Variables and Scope.................. Chapter 2 - Types, Operators and Expressions..................... 2.1 Variable Names................................. 2.2 Data Types and Sizes........................... 2.3 Constants...................................... 2.4 Declarations................................... 2.5 Arithmetic Operators........................... 2.6 Relational and Logical Operators............... 2.7 Type Conversions............................... 2.8 Increment and Decrement Operators.............. 2.9 Bitwise Operators.............................. 2.10 Assignment Operators and Expressions.......... 2.11 Conditional Expressions....................... 2.12 Precedence and Order of Evaluation............ Chapter 3 - Control Flow......................................... 3.1 Statements and Blocks.......................... 3.2 If-Else........................................ 3.3 Else-If........................................ 3.4 Switch......................................... 3.5 Loops - While and For.......................... 3.6 Loops - Do-While............................... 3.7 Break and Continue............................. 3.8 Goto and labels................................ Chapter 4 - Functions and Program Structure...................... 4.1 Basics of Functions............................ 4.2 Functions Returning Non-integers............... 4.3 External Variables............................. 4.4 Scope Rules.................................... 4.5 Header Files................................... 4.6 Static Variables................................ 4.7 Register Variables.............................. 4.8 Block Structure................................. 4.9 Initialization.................................. 4.10 Recursion...................................... 4.11 The C Preprocessor............................. 4.11.1 File Inclusion........................ 4.11.2 Macro Substitution.................... 4.11.3 Conditional Inclusion................. Chapter 5 - Pointers and Arrays.................................. 5.1 Pointers and Addresses......................... 5.2 Pointers and Function Arguments................ 5.3 Pointers and Arrays............................ 5.4 Address Arithmetic............................. 5.5 Character Pointers and Functions............... 5.6 Pointer Arrays; Pointers to Pointers........... 5.7 Multi-dimensional Arrays....................... 5.8 Initialization of Pointer Arrays............... 5.9 Pointers vs. Multi-dimensional Arrays.......... 5.10 Command-line Arguments........................ 5.11 Pointers to Functions......................... 5.12 Complicated Declarations...................... Chapter 6 - Structures........................................... 6.1 Basics of Structures........................... 6.2 Structures and Functions....................... 6.3 Arrays of Structures........................... 6.4 Pointers to Structures......................... 6.5 Self-referential Structures.................... 6.6 Table Lookup................................... 6.7 Typedef........................................ 6.8 Unions......................................... 6.9 Bit-fields..................................... Chapter 7 - Input and Output..................................... 7.1 Standard Input and Output....................... 7.2 Formatted Output - printf....................... 7.3 Variable-length Argument Lists.................. 7.4 Formatted Input - Scanf......................... 7.5 File Access..................................... 7.6 Error Handling - Stderr and Exit................ 7.7 Line Input and Output........................... 7.8 Miscellaneous Functions......................... 7.8.1 String Operations...................... 7.8.2 Character Class Testing and Conversion. 7.8.3 Ungetc................................. 7.8.4 Command Execution...................... 7.8.5 Storage Management..................... 7.8.6 Mathematical Functions................. 7.8.7 Random Number generation............... Chapter 8 - The UNIX System Interface............................ 8.1 File Descriptors............................... 8.2 Low Level I/O - Read and Write................. 8.3 Open, Creat, Close, Unlink..................... 8.4 Random Access - Lseek.......................... 8.5 Example - An implementation of Fopen and Getc.. 8.6 Example - Listing Directories.................. 8.7 Example - A Storage Allocator.................. Appendix A - Reference Manual.................................... A.1 Introduction................................... A.2 Lexical Conventions............................ A.2.1 Tokens................................ A.2.2 Comments.............................. A.2.3 Identifiers........................... A.2.4 Keywords.............................. A.2.5 Constants............................. A.2.6 String Literals....................... A.3 Syntax Notation................................ A.4 Meaning of Identifiers......................... A.4.1 Storage Class......................... A.4.2 Basic Types........................... A.4.3 Derived types......................... A.4.4 Type Qualifiers....................... A.5 Objects and Lvalues............................ A.6 Conversions.................................... A.6.1 Integral Promotion.................... A.6.2 Integral Conversions.................. A.6.3 Integer and Floating.................. A.6.4 Floating Types........................ A.6.5 Arithmetic Conversions................ A.6.6 Pointers and Integers................. A.6.7 Void.................................. A.6.8 Pointers to Void...................... A.7 Expressions.................................... A.7.1 Pointer Conversion.................... A.7.2 Primary Expressions................... A.7.3 Postfix Expressions................... A.7.4 Unary Operators....................... A.7.5 Casts................................. A.7.6 Multiplicative Operators.............. A.7.7 Additive Operators.................... A.7.8 Shift Operators....................... A.7.9 Relational Operators.................. A.7.10 Equality Operators................... A.7.11 Bitwise AND Operator................. A.7.12 Bitwise Exclusive OR Operator........ A.7.13 Bitwise Inclusive OR Operator........ A.7.14 Logical AND Operator................. A.7.15 Logical OR Operator.................. A.7.16 Conditional Operator................. A.7.17 Assignment Expressions............... A.7.18 Comma Operator.......................... A.7.19 Constant Expressions.................... A.8 Declarations..................................... A.8.1 Storage Class Specifiers................. A.8.2 Type Specifiers.......................... A.8.3 Structure and Union Declarations......... A.8.4 Enumerations............................. A.8.5 Declarators.............................. A.8.6 Meaning of Declarators................... A.8.7 Initialization........................... A.8.8 Type names............................... A.8.9 Typedef.................................. A.8.10 Type Equivalence........................ A.9 Statements....................................... A.9.1 Labeled Statements....................... A.9.2 Expression Statement..................... A.9.3 Compound Statement....................... A.9.4 Selection Statements..................... A.9.5 Iteration Statements..................... A.9.6 Jump statements.......................... A.10 External Declarations........................... A.10.1 Function Definitions.................... A.10.2 External Declarations................... A.11 Scope and Linkage............................... A.11.1 Lexical Scope........................... A.11.2 Linkage................................. A.12 Preprocessing................................... A.12.1 Trigraph Sequences...................... A.12.2 Line Splicing........................... A.12.3 Macro Definition and Expansion.......... A.12.4 File Inclusion.......................... A.12.5 Conditional Compilation................. A.12.6 Line Control............................ A.12.7 Error Generation........................ A.12.8 Pragmas................................. A.12.9 Null directive.......................... A.12.10 Predefined names....................... A.13 Grammar......................................... Appendix B - Standard Library.................................... B.1.1 File Operations................................ B.1.2 Formatted Output......................... B.1.3 Formatted Input.......................... B.1.4 Character Input and Output Functions..... B.1.5 Direct Input and Output Functions........ B.1.6 File Positioning Functions............... B.1.7 Error Functions.......................... B.2 Character Class Tests: ................. B.3 String Functions: ..................... B.4 Mathematical Functions: ................. B.5 Utility Functions: ....................

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