The following program cannot compile in gcc. But it compiles OK with g++ and MSC++ with .c
extension.
#include <math.h>
#include <stdio.h>
int main()
{
double t = 10;开发者_运维问答
double t2 = 200;
printf("%lf\n", sqrt(t*t2));
return 0;
}
My system is CentOS, the version info.
> gcc --version
gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
The error info:
> gcc test.c
/tmp/ccyY3Hiw.o: In function `main':
test.c:(.text+0x55): undefined reference to `sqrt'
collect2: ld returned 1 exit status
Is this a bug?
Any one can do a test for me?
Have you linked the math library?
gcc -lm test.c -o test
Add the math library with flag -lm
> gcc test.c -lm
Try gcc -lm test.c -o test
For gcc, you need to tell it to link the math library in, by adding -lm to your gcc call.
Everybody has been saying this, but I will too. You have to "tell" gcc to link to the math library. When you compile, instead of saying gcc test.c
, you have to say gcc -lm test.c
. I wish that I could just #include
math.h and not have to do anything else.
The thing is, gcc -lm test.c -o test
won't work because gcc will treat the -lm as a compiler and not a linker option. You need to put the -lm at the end of the command instead, i.e. gcc -o test test.c -lm
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