header file error

This is a discussion on header file error within the C Programming forums, part of the General Programming Boards category; Hi everyone, if I include the header, - #include "Test_Case.h" and also define it, #ifndef _TEST_CASE_H #define _TEST_CASE_H code ~~ ...

  1. #1
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    header file error

    Hi everyone,

    if I include the header,

    - #include "Test_Case.h"

    and also define it,

    #ifndef _TEST_CASE_H
    #define _TEST_CASE_H
    code ~~
    #endif

    anyone know why do i still get this :

    one or more multiply defined symbols found
    Error executing link.exe.

  2. #2
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    We'd have to see more code. Be warned that variables and macros starting with an underscore '_' are reserved to whoever implemented the libraries that come with your compiler. Basically, that means that if you create a variable that starts with an underscore, it might already be used and it will cause an error. This is probably not the case here so we need to see more code. Give us only the pre-compiler code (i.e. lines that start with #) since this is the linking part and as you can tell by the error, the linking has failed (which comes before compiling).

  3. #3
    CSharpener vart's Avatar
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    the linking has failed (which comes before compiling).
    Always thought that linkage is done after compilation...

    one or more multiply defined symbols found
    Check that you don't define global variables in your header.
    And you should not put any function bodies there also.
    The whole header file text will be usefull
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  4. #4
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    If it's a linker error, check that you haven't linked any object file multiple times. If you follow the standard convention of declaration in header files and implementation in source files, the code should compile without problems, as far as I see.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

  5. #5
    and the hat of wrongness Salem's Avatar
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    > anyone know why do i still get this :
    Because include guards only work just the once for each source file you include it in.

    Including the same file in several source files will create several definitions, if your header file contains definitions.

    The real answer is to make sure your header only contains declarations.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  6. #6
    Frequently Quite Prolix dwks's Avatar
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    Be warned that variables and macros starting with an underscore '_' are reserved to whoever implemented the libraries that come with your compiler. Basically, that means that if you create a variable that starts with an underscore, it might already be used and it will cause an error.
    Actually, identifiers starting with an underscore followed by another underscore or an uppercase letter are reserved. That is, these are reserved:
    Code:
    _INCLUSION_GUARD
    __reserved
    ___something
    But these aren't:
    Code:
    _variable
    _256
    [edit] Sort of like this, if you like REs:
    Code:
    if(name =~ /_[A-Z_]/) { reserved(); }
    [/edit]

    One example of what Salem said is declaring a non-static global variable in a header file. Including this header file multiple times would cause an error much like you posted.
    dwk

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  7. #7
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    Thanks everyone.
    I manage to solve it.

  8. #8
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    Could u please tell us, how did u manage to solve it??
    S_ccess is waiting for u. Go Ahead, put u there.

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