How do I solve this error

Question

1.00/5 (1 vote)

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/usr/bin/ld: /tmp/cc5LfrxC.o: in function `main':
100-main.c:(.text+0x14): undefined reference to `is_palindrome'
/usr/bin/ld: 100-main.c:(.text+0x39): undefined reference to `is_palindrome'
/usr/bin/ld: 100-main.c:(.text+0x5e): undefined reference to `is_palindrome'
/usr/bin/ld: 100-main.c:(.text+0x83): undefined reference to `is_palindrome'
collect2: error: ld returned 1 exit status
root@d

Code that produced the error -

C

/**
* main - check the code
*
* Return: Always 0.
*/
int main(void)
{
int r;

r = is_palindrome("level");
printf("%d\n", r);
r = is_palindrome("redder");
printf("%d\n", r);
r = is_palindrome("test");
printf("%d\n", r);
r = is_palindrome("step on no pets");
printf("%d\n", r);
return (0);
}

What I have tried:

i have delete it several times and redo it, i have tried bettycode, bit it says space at the start, i have tried gcc and is giving me this undefined reference.
i cant seems to understand what i did wrong

Posted 6-Jul-23 4:54am

Claire Tochi

Updated 6-Jul-23 20:22pm

Graeme_Grant

v6

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Comments

Mike Hankey 6-Jul-23 11:03am

Without the code that produced the error we are not able to help you.

Claire Tochi 6-Jul-23 11:10am

i will present the code just now

#include "main.h"
#include <stdio.h>

/**
* main - check the code
*
* Return: Always 0.
*/
int main(void)
{
int r;

r = is_palindrome("level");
printf("%d\n", r);
r = is_palindrome("redder");
printf("%d\n", r);
r = is_palindrome("test");
printf("%d\n", r);
r = is_palindrome("step on no pets");
printf("%d\n", r);
return (0);
}

Claire Tochi 6-Jul-23 11:11am

i have produce the @Mike Hankey, please review

Patrice T 6-Jul-23 12:47pm

Use Improve question to update your question.
So that everyone can pay attention to this information.

Dave Kreskowiak 6-Jul-23 13:10pm

Like I said in my solution below, you don't have a function called "is_palindrome" defined. You're calling a function that doesn't exist in your code.

You have to define and write the code for the "is_palindrome" function.

Claire Tochi 6-Jul-23 11:13am

0x08. C - Recursion

here is the task name

Claire Tochi 6-Jul-23 11:08am

how do i solve an undefined reference is_palindrome.c error 1d returned 1 exist status
i really need a reponse please

2 solutions

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CPallini · Answer 1 · 2023-07-06T20:22:00

In the posted code is missing:

The inclusion of the stdio.h header.
The declaration of the is_palindrome function.
The definition of the is_palindrome function.

Therefore, if you try to compile it, as it stands, the compiler will output something like

test.c: In function ‘main’:
test.c:6:6: warning: implicit declaration of function ‘is_palindrome’ [-Wimplicit-function-declaration]
    6 |  r = is_palindrome("level");
      |      ^~~~~~~~~~~~~
test.c:7:2: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
    7 |  printf("%d\n", r);
      |  ^~~~~~
test.c:7:2: warning: incompatible implicit declaration of built-in function ‘printf’
test.c:1:1: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
  +++ |+#include <stdio.h>
    1 |                                                                                                                                                                                                  
/usr/bin/ld: /tmp/ccqqE0qs.o: in function `main':                                                                                                                                                        
test.c:(.text+0x19): undefined reference to `is_palindrome'                                                                                                                                              
/usr/bin/ld: test.c:(.text+0x43): undefined reference to `is_palindrome'                                                                                                                                 
/usr/bin/ld: test.c:(.text+0x6d): undefined reference to `is_palindrome'                                                                                                                                 
/usr/bin/ld: test.c:(.text+0x97): undefined reference to `is_palindrome'                                                                                                                                 
collect2: error: ld returned 1 exit status

If you provide (together with stdio.h header inclusion) the is_palindrome function declaration

C

#include <stdio.h>

int is_palindrome(const char * ); // 'is_palindrome' function declaration

int main(void)
{
  int r;

  r = is_palindrome("level");
  printf("%d\n", r);
  r = is_palindrome("redder");
  printf("%d\n", r);
  r = is_palindrome("test");
  printf("%d\n", r);
  r = is_palindrome("step on no pets");
  printf("%d\n", r);
  return (0);
}

Then the compiler will output:

/usr/bin/ld: /tmp/ccelevUP.o: in function `main':                                                                                                                                                        
test.c:(.text+0x14): undefined reference to `is_palindrome'                                                                                                                                              
/usr/bin/ld: test.c:(.text+0x39): undefined reference to `is_palindrome'
/usr/bin/ld: test.c:(.text+0x5e): undefined reference to `is_palindrome'
/usr/bin/ld: test.c:(.text+0x83): undefined reference to `is_palindrome'
collect2: error: ld returned 1 exit status

These linker errors are telling you the defintion of the is_palindrome is missing.

Eventually the following piece of code, providing both the is_palindrome declaration and definition will happily compile:

C

#include <stdio.h>

int is_palindrome(const char * ); // 'is_palindrome' function declaration

int main(void)
{
  int r;

  r = is_palindrome("level");
  printf("%d\n", r);
  r = is_palindrome("redder");
  printf("%d\n", r);
  r = is_palindrome("test");
  printf("%d\n", r);
  r = is_palindrome("step on no pets");
  printf("%d\n", r);
  return (0);
}

int is_palindrome(const char * s ) // 'is_palindrome' function definition
{
  // TODO: check if the passed string is palindrome, and return 1 if it is.

 return 0; // that is: 'not palindrome'
}

Dave Kreskowiak · Answer 2 · 2023-07-06T05:02:00

Solution 1

First, that's not C#. That's plain old C.

You're trying to use a function that hasn't been defined in the code yet. In C, a function has to be defined, or at least forward declared, before the compiler comes across code that calls that function.

Posted 6-Jul-23 5:02am

Dave Kreskowiak