Thread: incompatible implicit declaration of built-in function

  1. #1
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    incompatible implicit declaration of built-in function

    warning: incompatible implicit declaration of built-in function ‚strlen‚
    warning: undefined reference to `sqrt'
    warning: implicit declaration of function ‚strcmp‚
    warning: implicit declaration of function ‚strcat‚
    warning: incompatible implicit declaration of built-in function ‚strcat‚

    I have all the necessary includes, do i need to do some extra command to get this to compile properly?

    How do i fix that when my SSH Secure Shell compiles the file, i get a bunch of those..

  2. #2
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Oonej
    I have all the necessary includes
    I'll believe it when I see it.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    and the hat of int overfl Salem's Avatar
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    Well you would need to post your code to back up your assertion that you're including all the right files.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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    #include <stdio.h>
    #include <stdlib.h>
    #include <ctype.h>
    #include <math.h>

    can't post code, as this is a class project and students in my class view them... not looking to get a F for "cheating" lol

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    btw - this compiles fine and works 100% in my DevC++ IDE, but doesn't compile on the SSH server, do i need to amend the header files in the compile on the SSH or something?

  6. #6
    C++ Witch laserlight's Avatar
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    You're missing <string.h> for strlen, strcmp and strcat.

    Also, to solve "undefined reference to `sqrt'" you may need to explicitly link to the math library, e.g., with -lm
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    too many arguments for format /tmp/cc3hMW6h.o: In function [function name]

    what does that refer to?

    and also how do i amend the math.h file with -lm? never used it before

  8. #8
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Oonej
    too many arguments for format /tmp/cc3hMW6h.o: In function [function name]

    what does that refer to?
    My guess is that you used too many arguments for format

    Perhaps this has something to do with printf. Or maybe with a function call. I'm not sure because you provided so little information that only someone who has come across that error message before and remembers the context and solution is likely to be able to accurately tell you the problem and solution.

    Quote Originally Posted by Oonej
    and also how do i amend the math.h file with -lm? never used it before
    What compiler are you using? Are you compiling on the command line, or from an IDE?
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    SSH Secure Shell - command line

  10. #10
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Oonej
    SSH Secure Shell - command line
    SSH Secure Shell is not a compiler

    Let's suppose you are using gcc. Currently, you might be running:
    Code:
    gcc -o program source.c
    If my guess is correct, it may become:
    Code:
    gcc -o program -lm source.c
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  11. #11
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    Never modify header files like math.h present on the system.
    Besides -lm is a linker directive specified on the command line.

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