undefined reference to

This is a discussion on undefined reference to within the C Programming forums, part of the General Programming Boards category; I keep getting compile error: ../../thread/thread.c:318: undefined reference to `pid_alloc` ../../thread/thread.c:350: undefined reference to `pi_get` thread.c looks like: Code: .... ...

  1. #1
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    undefined reference to

    I keep getting compile error:

    ../../thread/thread.c:318: undefined reference to `pid_alloc`
    ../../thread/thread.c:350: undefined reference to `pi_get`

    thread.c looks like:
    Code:
    ....
    #include <pid.h>
    ....
    line 318:   assert(pid_alloc(tid));
    ...
    line 350:   struct pidinfo *wait_t = pi_get(tid)
    ...
    pid.h:
    Code:
    struct pidinfo *pi_get(pid_t pid);
    ...
    int pid_alloc(pid_t *retval)
    ...
    pid.c:
    Code:
    ...
    struct pidinfo *
    pi_get(pid_t pid)
    {
    ...
    }
    ...
    int
    pid_alloc(pid_t *reval)
    {
    ...
    }
    ...
    I can't understand why I'm getting this error when pid.h and pid.c seem to be fine

  2. #2
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by shaun84
    I keep getting compile error:

    ../../thread/thread.c:318: undefined reference to `pid_alloc`
    ../../thread/thread.c:350: undefined reference to `pi_get`
    Looks more like a linker error. Are you attempting to link to to proper library?
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  3. #3
    The C eater *munch*
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    found it

    this line is wrong
    Code:
    #include <pid.h>

  4. #4
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    but w/o <pid.h> none of the functions defined in it will work.

  5. #5
    The C eater *munch*
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    you obviously don't get what i meant , I'm not saying that line isn't supposed to be there, it's just wrong

    you put "<>" whenever you are reffering to a built in library, whereas when you refer to an external library of your own, you have to use .... (fill in the blanks)
    Last edited by yxunomei; 10-14-2006 at 06:17 AM.

  6. #6
    Registered User ssharish2005's Avatar
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    Quote Originally Posted by yxunomei
    when you refer to an external library of your own, you have to use .... (fill in the blanks)
    i think u can change this sentence to like "when u refer to an external library of your own which is located in the current directory, you have to use ..."

    because even thought if u have your own .h file and when u place it in include directory u will refer that header file using <>

    ssharish2005

  7. #7
    The C eater *munch*
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    ah yes, i forgot to include that possibility

    Code:
    #include <thatPossibility.h>

  8. #8
    Reverse Engineer maxorator's Avatar
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    Quote Originally Posted by yxunomei
    you obviously don't get what i meant , I'm not saying that line isn't supposed to be there, it's just wrong

    you put "<>" whenever you are reffering to a built in library, whereas when you refer to an external library of your own, you have to use .... (fill in the blanks)
    You really don't seem to understand what a library is. Library is not a HEADER file. You INCLUDE header files and you LINK to library files.
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  9. #9
    The C eater *munch*
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    whoa now dat's a new knowledge for me...

    thank's sir!

  10. #10
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    Thanks for the feedback guys.

    From what I understand you have to use different syntax when referencing headers files that are not in the "include" directory.

    However, I have pid.h along with all my other header files that are "included" in thread.c inside the include folder... therefore all includes are of the form "#include <filename.h>"

    Could there be a problem within my pid.c that causes this?

  11. #11
    Frequently Quite Prolix dwks's Avatar
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    No, I would say that the problem is that you're not linking to the correct library, as Dave_Sinkula said in the first reply of this thread. For GCC, the option might be -lbsd-compat or -lpthread or -lthread or something else entirely. (I'm not sure where those functions are.)
    dwk

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  12. #12
    The C eater *munch*
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    try this

    Code:
    #include "pid.h"
    notice the double quotes

    if that doesn't work, try dwk's suggestion

  13. #13
    Reverse Engineer maxorator's Avatar
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    Undefined reference IS a linker error.
    You cannot get rid of it by including header files.
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