undefined reference to `sqrt' when using math.h

This is a discussion on undefined reference to `sqrt' when using math.h within the C Programming forums, part of the General Programming Boards category; Just like the title says.. I get undefined reference to `sqrt' error and i included math.h Using GCC by the ...

  1. #1
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    undefined reference to `sqrt' when using math.h

    Just like the title says..

    I get
    undefined reference to `sqrt'
    error and i included math.h


    Using GCC by the way, in linux.

  2. #2
    int x = *((int *) NULL); Cactus_Hugger's Avatar
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    "undefined reference" is a linker error - meaning that you didn't link with the code for the function it's complaining about. (Most of the times, #including something will not fix this)

    For sqrt(), add -lm to your linker flags.
    long time; /* know C? */
    Unprecedented performance: Nothing ever ran this slow before.
    Any sufficiently advanced bug is indistinguishable from a feature.
    Real Programmers confuse Halloween and Christmas, because dec 25 == oct 31.
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    recursion (re - cur' - zhun) n. 1. (see recursion)

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    Quote Originally Posted by Cactus_Hugger View Post
    "undefined reference" is a linker error - meaning that you didn't link with the code for the function it's complaining about. (Most of the times, #including something will not fix this)

    For sqrt(), add -lm to your linker flags.
    What is a linker flags?

    I'm using gcc how should i do it?

  4. #4
    int x = *((int *) NULL); Cactus_Hugger's Avatar
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    Example:
    Code:
    $ gcc -c -o main.o main.c
    $ gcc -c -o second.o second.c
    $ gcc -o myprogram main.o second.o -lm
      or, if you're doing it all in one line:
    $ gcc -o myprogram main.c second.c -lm
    long time; /* know C? */
    Unprecedented performance: Nothing ever ran this slow before.
    Any sufficiently advanced bug is indistinguishable from a feature.
    Real Programmers confuse Halloween and Christmas, because dec 25 == oct 31.
    The best way to accelerate an IBM is at 9.8 m/s/s.
    recursion (re - cur' - zhun) n. 1. (see recursion)

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    Thanks!

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