Re: programming in Red hat 7.2 include error without -O

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Hi,

  The "sqrt" function is in libm, you should use: gcc PROGRAM_NAME -lm

Venkatesh

> 
> Hi, all
> 
> I had a function and cc it in redhat 7.2,
> but if I use
> $gcc PROGRAM_NAME,
> there will be error :
> 
> /tmp/ccAXzZTF.o: In function `main':
> /tmp/ccAXzZTF.o(.text+0x32): undefined reference to `sqrt'
> collect2: ld returned 1 exit status
> 
> but if I use -O or -O2 to gcc, it works well !!
> I do not know why, the following is source code
> 
> 
> #include <stdio.h>
> #include <math.h>
> 
> int main(void)
> {
> 
> double pi = M_PI;
> double pisqrt;
> long i;
> 
> for (i = 0; i < 10000000; ++i) {
> pisqrt = sqrt(pi);
> }
> return 0;
> }
> 
> 
> 
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> Redhat-devel-list@redhat.com
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> 



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