Question

c语言被提示 undefined reference to

#include <stdio.h>
#include <string.h>
float in(float,float);
int main(void)
{
float a,b,v;
printf("enter two number,q to quit");
while(scanf("%f %f",&a,&b)==2)

{
printf("it is %f\n",in(a,b));
}

float in(float c,float d)

{
float SUM;
for(c;c<d;c++)
{

SUM+=c;
c++;
return(SUM);

}
}
}
请问这是什么问题啊？提示in函数无效，是不是语法哪里出了问题，麻烦请帮忙看一下，蟹蟹O(∩_∩)O

Answer 1

假设你已经正确编译和安装了Sqlite，写个测试程序来测试：#include#include#include"sqlite3.h"intmain(void){sqlite3*db=NULL;char*zErrMsg=0;intrc;rc=sqlite3_open("test1.db",&db);if(rc){fprintf(stderr,"Can'topendatabase:%s\n",sqlite3_errmsg(db));sqlite3_close(db);exit(1);}elseprintf("openmydatasuccessfully!\n");sqlite3_close(db);return0;}用GCC来编译的时候总是会出现错误，编译的命令如下gcc-static-ohello-lsqlite3-L/usr/local/lib-I/usr/local/includehello.c错误信息如下/tmp/ccKeKpX9.o(.text+0x37):Infunction`main'::undefinedreferenceto`sqlite3_open'/tmp/ccKeKpX9.o(.text+0x51):Infunction`main'::undefinedreferenceto`sqlite3_errmsg'/tmp/ccKeKpX9.o(.text+0x73):Infunction`main'::undefinedreferenceto`sqlite3_close'/tmp/ccKeKpX9.o(.text+0x9b):Infunction`main'::undefinedreferenceto`sqlite3_close'collect2:ldreturned1exitstatus那么，恭喜你中招了。错误根本不在SQLITE也不在你的程序，而在GCC。Gcc的编译参数是有顺序的。正确的编译命令是：gcc-ohello-L/usr/local/lib-I/usr/local/include-statichello.c-lsqlite3

Answer 2

你这是什么结构，为什么在main函数里定义float in(float c,float d)函数
#include <stdio.h>
#include <string.h>
float in(float,float);
int main(void)
{
float a,b,v;
printf("enter two number,q to quit");
while(scanf("%f %f",&a,&b)==2)
{
printf("it is %f\n",in(a,b));
}

return 0;
}

float in(float c,float d)
{
float SUM;
for(c;c<d;c++)
{
SUM+=c;
c++;
}
return(SUM);
}