Home/ Questions/Ways to resolve the error - clang: error: linker command failed with exit code 1
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Juliette Faure
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Asked: 2022-05-18T10:42:24+00:00 In:

Ways to resolve the error – clang: error: linker command failed with exit code 1

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Hi developer experts, I have a small but frustrating use case, and so far, I couldn’t get my head around this problem & ideal solution. I am running my command and facing one problem with the clang: error: linker command failed with exit code 1. Below is the command I used:

#include <stdio.h>
 
 int power(int m, int n);
 
 int main()
 {
 int i;
 
 for (i=0; 1<10; ++i)
  printf("%d %d %d\n", i, power(2,i), power(-3,i));
 
 return 0;
 }

When I run it, I get the following error:

Undefined symbols for architecture x86_64:
  "_power", referenced from:
  _main in main.o
 ld: symbol(s) not found for architecture x86_64
 clang: error: linker command failed with exit code 1 (use -v to see invocation)

I am looking forward to gaining some knowledge from all experts. Thank you, guys!

linker command failed with exit code 1
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2 Answers

  1. Best Answer
    Expert

    The cause:

    Why do I get clang: error: linker command failed with exit code 1?

    There is no definition in code in the function which you has just declared. Compiler(here clang), cannot link power function with its definition at the time of linking so linker throws an error in this type of situation and the error happens.

    Solution:

    If you define

    int power(int x, int y) 
 { 
 \*do calculation*/
 }

    Your power function declaration will be linked to its definition by the linker. You won’t get an error. I have created function for integer number as below:

    #include <stdio.h>
int power(int base, int exp);
int main()
{
int i;

for (i=0; i<10; ++i)
 printf("%d %d %d\n", i, power(2,i), power(-3,i));

return 0;
}

int power(int base, int exp)
{
 int result = 1;
 while (exp)
 {
 if (exp & 1)
 result *= base;
 exp >>= 1;
 base *= base;
 }

 return result;
}

    This gcc file.c compilation is required.

    • 8

  2. The definition of function int power (int base,int n) was not included in your book’s main pages.

    You must define the function that you are declaring prototype of.

    The following definition will ensure that your code compiles exactly as you want it to. 

    int power (int base,int n){
int i,p;
p=1;
for (i=1;i<=n;++i)
p=p*base;
return p;
}

    PRE-EDIT NOW THIS ISN’T RELEVANT, BUT USEFULL

    You may want to use the math.h function pow(), I believe. 

    double pow(double a, double b)

    C library function pow(double a, double b) returns a, which is twice as powerful as b. This function returns double values so that "%lf" will print the correct specifier.

    You will only need to include the header file in this instance 

    #include<math.h>

    Include it in your program.

    It is not necessary to provide function declaration int power(int m, int n);

    Your error is caused by I being given as the parameter to pow(). This is because pow() will compile your source code after you have included math.h and used pow() to replace i with any other integer numbers. 

    printf("%lf %lf %lf\n", i, pow(2,3), pow(3,2));

    You will get a good result if you combine it with 

    for (i=0; i<10; ++i){
printf("%lf %lf %lf\n", i, pow(2,i), pow(-3,i));
}

    It throws the same error, so pow() should only accept constants input.

    You can also declare if math.h is not required. 

    extern double pow (double base, double exponent);

    This will allow you to link with the library code directly without the use of the math.h include files. Here is an example. 

    int main() {
extern double pow (double base, double exponent);
printf("%lf",pow( 8.0, 8.0 ));
return 0;
}

    You can find more information on pow() on the man page for Linux, i.e. man pow.

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