CODEWITHSUNDEEP
c
SSR
SSR

Reputation: 21

Calling from one function to other functions within the same C program

I'm trying to call other adjacent functions (delay() and delay_ex()) from a function (bitcheck()) as shown below and as expected, the compiler has thrown an error that delay() and delay_ex() functions weren't declared in the scope and I understood that we can't call functions other than from the main. So, I declared these delay() and delay_ex() functions in a header file and called from this program by including the header file, it worked well. So, is there any other such way to make this work?

void bitcheck()
{
    int i;
    for(i=0;i<NELEMS(array); i++)
    {       
        delay();
        AP_CMU->DIVIDER = freq_def[0];
        encryption(array,i);
        delay();
        // LCD_DisplayUint32(i,0,array[i]);
        AP_CMU->DIVIDER = freq_def[6];
        delay_ex(10);
        decryption(intr_array,i);
        delay_ex(10);
        // LCD_DisplayUint32(i,10,array[i]);
    }

}

void delay()
{
    int i;
    for (i = 0; i < 100000; i++) {
        __NOP();
    }
}

void delay_ex(int j)
{
    for(int s=0; s < j; s++)
    {
        for ( int i = 0; i < 10000; i++) {
            __NOP();
        }

    }
}

Upvotes: 0

Views: 164

Answers (3)

sapensadler
sapensadler

Reputation: 386

You can write your functions above the code that calls them like:

void foo() {
}

void bar() {
}
int main () {
    foo();
    bar();
}

You can also forward declare functions like: 

void foo();
void bar();
int main () {
    foo();
    bar();
}
void foo() {
}

void bar() {
}

Or you can put them in a header file and include it

file.h:

void foo();
void bar();

file.c:

#include "file.h"
int main () {
    foo();
    bar();
}
void foo() {
}

void bar() {
}

Upvotes: 4

Clifford
Clifford

Reputation: 93566

The compiler works in a single pass, as such when bitcheck() is parsed, the signatures of delay() and delay_ex() are not known, so the compiler cannot verify the call is type-correct.

The rule is declare or define before use; there are two possible solutions:

  • Define bitcheck() after the definition of delay() and delay_ex()
  • Forward-declare delay() and delay_ex().

By declaring the functions in a header and including it before defining bitcheck(), you used the second of these solutions, but use of an include file was not essential - #include does noting more than insert the file content into the translation-unit prior to compilation. This is useful when the symbols will be called from a different translation-unit than that in which they are defined; if that is not intended the declarations may be written directly rather then #include'd, and should also be declared static to avoid external-linkage and potential name clashes with other translation-units.

Upvotes: 2

Zackary Murphy
Zackary Murphy

Reputation: 411

You need to define delay and delay_ex before bitcheck. Simply moving those two functions above bitcheck should suffice.

Upvotes: 0

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