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1¡¢ÓÃGCC±àÒë
1.1¡¢´´½¨Ô´Îļþ
(main.c) C Ô´Îļþ - main.c
#include
#include “reciprocal.hpp”
int main (int argc, char **argv)
{
    int i;
    i = atoi (argv[1]);
    printf (“The reciprocal of %d is %g\n”, i, reciprocal (i));
    return 0;
}
(reciprocal.cpp) C++ Ô´Îļþ - reciprocal.cpp
#include
#include “reciprocal.hpp”
double reciprocal (int i) {
    // I should be non-zero.
    assert (i != 0);
    return 1.0/i;
}
(reciprocal.hpp) Í·Îļþ - reciprocal.hpp
#ifdef __cplusplus
    extern “C” {
#endif
    extern double reciprocal (int i);
#ifdef __cplusplus
    }
#endif
1.2¡¢±àÒëÔ´Îļþ
±àÒëmain.c:
% gcc -c main.c
±àÒëreciprocal.cpp:
% g++ -c reciprocal.cpp
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% g++ -c -I ../include reciprocal.cpp
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¶ÔÓÚÈçϳÌÐòdefinemacro.c:
#include "stdio.h"
#include "stdlib.h"
int main(int argc, char** argv){
        int i = 3;
#ifdef CHANGEVALUE
        i = 4;
#endif
        printf("i = %d\n", i);
        printf("PT = %f\n", PI);
}
Èç¹û±àÒëʱÃüÁîÐÐΪgcc definemacro.c£¬»á±¨‘PI’ undeclared´íÎó¡£
Èç¹û±àÒëʱÃüÁîÐÐΪgcc -D PI=3.14 definemacro.c£¬ÔòÊä³öÈçÏ£º
i = 3
PT = 3.140000
Èç¹û±àÒëʱÃüÁîÐÐΪgcc -D PI=3.14 -D CHANGEVALUE definemacro.c£¬ÔòÊä³öÈçÏ£º
i = 4
PT = 3.140000
¿ÉÒÔÓÃGCC±àÒëʱÓÅ»¯´úÂë.
% g++ -c -O2 reciprocal.cpp
1.3¡¢Á´½Ó¶ÔÏóÎļþ
g++¿ÉÒÔ½«.o¶ÔÏóÎļþÁ´½Ó³É³ÌÐò
% g++ -o reciprocal main.o reciprocal.o
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