//fpoin1.c
#include<stdio.h>
#include<conio.h>
#include<fpoin.c>
void swap(int,int);
void main()
{
int i=0;
i++;
if(i<=5)
{
printf("%d",i);
swap(59,23);
getch();
}
//fpoin.c
#include<stdio.h>
#include<conio.h>
extern int i;
void swap(int ,int );
int main()
{
int i=3;
int p,q;
swap(p,q);
printf("\np=%dq=%d",p,q);
getch();
return 0;
}
void swap(int p,int q)
{
int t=p;
p=q;
q=t;
}
When I compile fpoin1, it says "fpoin.c not found", but both are in same directory.
What is missing?
This should fix it:
#include "fpoin.c"
Using "" or <> affects how the compiler searches for a file/header. You should use <> for "system" and "library" includes, and use "" when including your own files.
But, you shouldn't include a .c file. You should compile each of these, then link them together, using e.g. this gcc one-liner: gcc -Wall -o appname fpoin.c fpoin1.c
You will also need to decide which of your two main() functions you want to use. You must have exactly one main()
Additionally, your swap function will not work as you expect, since you pass its arguments by value. Try this:
void swap(int * p, int * q) {
int t=*p;
*p=*q;
*q=t;
}
...
swap(&p, &q)
Of course, you cannot then call swap(59,23) - There's no variables to modify. What was swap(59,23) supposed to do?
One normally only includes .h files, and links other .c files, but if you are going to include a local file, it should be done with "..." and not <...> delimiters, so:
#include "fpoin.c"
The <...> indicates a system header.
In your case, just switching to linking won't quite be good enough, as your main() will be multiply-defined either way. You might want to rethink your modularization a bit.
Using < and > in the #include says to the compiler that you are including a "standard header". Standard headers need not be real files on your disk: the compiler uses magic to include standard headers.
To include real files, use quotes in the #include line
#include "fpoin.c"
One more thing: don't get used to including code. Write files with declarations only and include them (tipically files with .h extension).
Related
I created a program in C that can find the determinant of a matrix
void fun1(); /*regardless of parameters they take*/
void fun2();
void fun3();
void fun4();
void fun5();
int global_var1; /*they are used among the above functions*/
int global_var2;
int global_var3;
int determinant;
int main(void){
int x,y;
for(x=0; x<something ; x++){
for (y=0 ; y<another_thing; y++){
fun1();
fun2();
fun3();
}
fun4();
fun5();
}
printf("Determinant is: %d\n", determinant);
return 0;
}
void fun1(){/*code goes here to process the matrix*/;}
void fun2(){/*code goes here to process the matrix*/;}
void fun3(){/*code goes here to process the matrix*/;}
void fun4(){/*code goes here to process the matrix*/;}
void fun5(){/*code goes here to process the matrix*/;}
Now I need to use this program to find the determinant of a given matrix in another project.
I created a header file, named it "matrix.h" and I replaced the int main(void) with int find_determinant() to be used in the new project.
the prototype of the second program:
#include "matrix.h"
int main(void){
find_determinant(); /*regardless of para it takes, it works perfectly*/
return 0;}
it works properly, nothing wrong with it, but the only problem that if I want to give this header file "matrix.h to someone to use it in his program, he can know the signature of other functions (useless for him alone and confusing) that were used to help in finding the determinant in int find_determinant().
My question is:
How can I hide (make them inaccessible) those functions and global variables and show only the int find_determinant() function in the second C file/program that contains #include "matrix.h" ?
Although you can put executable code in a header file, a good practice is to have your header file only contain declarations (for global variables) definitions and function prototypes. If you don't want to give your source code implementation, then you need to compile your functions into object code and provide the object file (either as a static archive or shared library) along with the header file. Whoever wants to use your function will then link his/her program to your objecet file/shared lib. This way, you can keep your source code implementation to yourself. Your header file would be:
#ifndef __SOME_MACRO_TO_PREVENT_MULTIPLE_INCLUSION__
#define __SOME_MACRO_TO_PREVENT_MULTIPLE_INCLUSION__
int find_determinant();
#endif
Beware of multiple inclusion problems (I have shown above how to avoid this so that if your matrix.h file is included several times, programs will still compile).
I am a rookie programmer here. I am trying to learn C. I am trying to have a main program run another file. However, I am getting compile time errors. My IDE says: Error. Implicit declaration of function print and also it says ROW and COL are not defined here. Of course I have 3 files and I don't see why I am getting these errors. I think I defined ROW and COL properly in the header file like you're supposed to. Can someone see a problem with this simple code? Right now I have the following code:
//p750_eightqueens.h
#ifndef P750_EIGHTQUEENS_H_INCLUDED
#define P750_EIGHTQUEENS_H_INCLUDED
#define ROW 8
#define COL 8
void go(int row, int col);
void print(int array[ROW][COL]);
#endif // P750_EIGHTQUEENS_H_INCLUDED
//p750_eightqueens.c
void go(int row, int col) {
int a[ROW][COL],i,j;
for(i=0;i<ROW;i++) {
for(j=0;j<COL;j++){
a[i][j]=(i==row&&j==col?1:0);
}
}
print(a);
}
void print(int array[ROW][COL]) {
int i,j;
for(i=0;i<ROW;i++) {
for(j=0;j<COL;j++){
printf("%i",a[i][j]);
if (j!=COL-1) printf(" ");
}
printf("\n");
}
}
//now in main.c
#include<stdio.h>
#include<stdlib.h>
#include "p750_eightqueens.h"
int main(){
go(4,4);
return 0;
}
You need to include your header file in p750_eightqueens.c, too.
Your .c files are compiled independently of each other, so your p750_eightqueens.c doesn't know about your defines and function declarations.
If you compile a C-program each compilation unit (.c-file) is compiled on it's own and needs all includes and declarations that are used in that file. After that you have object files (.o) which are then combined to a single executable by the linker. The linker searchs for the implementations of the used functions and puts it together so that different compilation units can call functions in others.
My files are
// main.c
#include <ClasseAusiliaria.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;
}
Use double quotes #include "ClasseAusiliaria.c" [Don't use angle brackets (< >) ]
And I prefer to save the file with .h extension In the same directory/folder.
TLDR:
Replace #include <ClasseAusiliaria.c> with
#include "ClasseAusiliaria.c"
Change your Main.c like so
#include <stdlib.h>
#include <stdio.h>
#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
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.
make a file classAusiliaria.h and in there provide your method signatures.
Now instead of including the .c file include this .h file.
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;
}
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 <> 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
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 <stdlib.h>
#include <stdio.h>
#include <ClasseAusiliaria.h>
int main(void)
{
int risultato;
risultato = addizione(5,6);
printf("%d\n",risultato);
}
write main.c like this -
caution : while linking both main.0 and ClasseAusiliaria.o should be
available to linker.
#include <stdlib.h>
#include <stdio.h>
extern int addizione(int a, int b)
int main(void)
{
int risultato;
risultato = addizione(5,6);
printf("%d\n",risultato);
}
I have been reading about C for a while now and decided lets write a little add program, nothing fancy at all. My understanding of C headers is that they are "interfaces" (such as like java and other languages) but where you can also define variable that either have set values or not..
So I wrote this:
#include <stdio.h>
#include <stdlib.h>
#include "sample.h"
int main(int argc, char** argv) {
printf("hello World\n");
add(12, 18);
return (EXIT_SUCCESS);
}
int add(int a, int b){
int value = a+b;
printf("value = %d\n", value);
return 0;
}
It has a header file that looks like such:
#ifndef SAMPLE_H_GUARD
#define SAMPLE_H_GUARD
int add(int a, int b);
#endif
I thought header files, and this is where I am lost on their definition, was suppose to define the use of add, so all I would have to do is call add - From my understanding, I define the rules of add and then implement the functionality of add....
Also, A lot of the material I have read shows one header file for multiple C files. where as a lot of projects today have one header per one c, meaning Sample.h belongs to Sample.c and nothing else.
Can some one shed some light on this?
Could I have done this like so:
main.c
#include <stdio.h>
#include <stdlib.h>
#include "sample.h"
int main(int argc, char** argv) {
printf("hello World\n");
add(12, 18);
return (EXIT_SUCCESS);
}
add.c
#include <stdio.h>
#include <stdlib.h>
#include "sample.h"
int add(int a, int b){
int value = a+b;
printf("value = %d\n", value);
return 0;
}
sample.h
#ifndef SAMPLE_H_GUARD
#define SAMPLE_H_GUARD
int add(int a, int b);
#endif
I believe in the book I was reading: C Programming Language they had a calculator example split up like this, my question is how does C know where add is defined? It knows the rules for it based on the header file, i think, but not where the actual implementation is ....
There example where they split of the files like such doe not have something like #include "add.c" all they do is include the header file in the files that either implement or use this functionality.
Note: obviously the calculator example and my example are going to be different but fundamentally the same - for those who have the book. I am just lost on how to use header files effectively and efficiently.
A header file in C would declare the function add for those modules that need it, but not define the function. The function is still to be defined in its own module (e.g., in your case, add.c).
So in general, to make a function foo available to several modules, you would normally:
Choose a header file (maybe it's own if there are other associated
defines, etc) to declare foo. For example, perhaps foo.h would
have void foo(...);
In some module, perhaps foo.c, you would define the complete
function foo.
In any module that wants to call foo, you would #include "foo.h"
(or whatever header you used) and call the function.
When you compile/link the code, you would make sure all modules,
including foo.o or whatever module has foo defined in it, were
present.
A declaration, given in the header file, provides (of course) the function name, the function return type as well as listing all the parameters and their types. This is all the compiler needs to know to figure out how to call the function from the calling module. At link time, addresses are all resolved so that the modules then know exactly where the function is in its own particular module.
My understanding of C headers is that they are "interfaces" (such as
like java and other languages) but where you can also define variable
that either have set values or not..
This is not correct. You cannot "define" variables - well, you can but that will cause multiple definitions error while compiling code if you include header more than once.
Could I have done this like so:
Regarding your code - both variants are correct. C language uses headers to read declarations and hence headers are optional as well. You can have your code split into as many as you want .h and .c files. Compiler will create an object file for each .c file. All .h files included in a c file are basically embedded in that C file "before compilation" i.e. in preprocessing phase. Linker then comes in picture which combines objects to produce the executable.
Please don't hesitate if something is not clear in my answer.
I am currently working on my first "serious" C project, a 16-bit vm. When I split up the files form one big source file into multiple source files, the linker (whether invoked through clang, gcc, cc, or ld) spits out a the error:
ld: duplicate symbol _registers in register.o and main.o for inferred
architecture x86_64
There is no declaration of registers anywhere in the main file. It is a uint16_t array if that helps. I am on Mac OS 10.7.3 using the built in compilers (not GNU gcc). Any help?
It sounds like you've defined a variable in a header then included that in two different source files.
First you have to understand the distinction between declaring something (declaring that it exists somewhere) and defining it (actually creating it). Let's say you have the following files:
header.h:
void printIt(void); // a declaration.
int xyzzy; // a definition.
main.c:
#include "header.h"
int main (void) {
xyzzy = 42;
printIt();
return 0;
}
other.c:
#include <stdio.h>
#include "header.h"
void printIt (void) { // a definition.
printf ("%d\n", xyzzy);
}
When you compile the C programs, each of the resultant object files will get a variable called xyzzy since you effectively defined it in both by including the header. That means when the linker tries to combine the two objects, it runs into a problem with multiple definitions.
The solution is to declare things in header files and define them in C files, such as with:
header.h:
void printIt(void); // a declaration.
extern int xyzzy; // a declaration.
main.c:
#include "header.h"
int xyzzy; // a definition.
int main (void) {
xyzzy = 42;
printIt();
return 0;
}
other.c:
#include <stdio.h>
#include "header.h"
void printIt (void) { // a definition.
printf ("%d\n", xyzzy);
}
That way, other.c knows that xyzzy exists, but only main.c creates it.