How to invoke function from external c file in C

Question

My files are     main c     include  add c   int main void        int result   add 5 6       printf   d n   result         and     add c    int add int a  int b        return a   b

User · Answer

You can include the  c files  no problem with it logically  but according to the standard to hide the implementation of the function but to provide the binaries  headers and source files techniques are used  where the headers are used to define the function signatures where as the source files have the implementation  When you sell your project to outside you just ship the headers and binaries libs and dlls  so that you hide the main logic behind your function implementation    Here the problem is you have to use    instead of  lt   as you are including a file which is located inside the same directory to the file where the inclusion happens  It is common to both  c and  h files

User · Answer

Change your Main c like so   include  lt stdlib h gt   include  lt stdio h gt   include  ClasseAusiliaria h   int main void      int risultato    risultato   addizione 5 6     printf   d n  risultato       Create ClasseAusiliaria h like so  extern int addizione int a  int b     I then compiled and ran your code  I got an output of  11

User · Answer

make a file classAusiliaria h and in there provide your method signatures   Now instead of including the  c file include this  h file

User · Answer

write main c like this -   caution   while linking both main 0 and ClasseAusiliaria o should be   available to linker     include  lt stdlib h gt    include  lt stdio h gt   extern int addizione int a  int b    int main void          int risultato       risultato   addizione 5 6        printf   d n  risultato

User · Answer

There are many great contributions here  but let me add mine non the less   First thing i noticed is  you did not make any promises in the main file that you were going to create a function known as add    This count have been done like this in the main file       int add int a  int b      before your main function  that way your main function would recognize the add function and try to look for its executable code   So essentially your files should be   Main c      int add int a  int b        int main void            int result   add 5 6           printf   d n   result             and    add c        int add int a  int b            return a   b

User · Answer

you shouldn t include c-files in other c-files  Instead create a header file where the function is declared that you want to call  Like so  file ClasseAusiliaria h   int addizione int a  int b      this tells the compiler that there is a function defined and the linker will sort the right adress to call out    In your Main c file you can then include the newly created header file     include  lt stdlib h gt   include  lt stdio h gt   include  lt ClasseAusiliaria h gt   int main void        int risultato      risultato   addizione 5 6       printf   d n  risultato

User · Answer

use  include  ClasseAusiliaria c    Dont use  angle brackets   lt        and I prefer save file with  h extension in the same Directory folder    include  ClasseAusiliaria h

User · Answer

You must declare  int add int a  int b    note to the semicolon  in a header file and include the file into both files  Including it into Main c will tell compiler how the function should be called  Including into  the second file will allow you to check that declaration is valid  compiler would complain if declaration and implementation were not matched    Then you must compile both   c files into one project  Details are compiler-dependent

[c] How to invoke function from external .c file in C?

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