CODEWITHSUNDEEP
ccompiler-errorsfunction-pointers
user1361391
user1361391

Reputation: 65

Compile errors in a test program with function pointers

I've written a simple C program to learn usage of function pointers:

#include <stdio.h>

int (*workA) ( char *vA );
int (*workB) ( char *vB );

int main( int argc, char * argv[] )
{
    char *strA = "Hello.";
    char *strB = "Bonjour.";

    int a = workA(strA);
    int b = workB(strB);

    printf("Return value of A = %d, B = %d.\n", a, b);

    return 0;
}

int (*workA)( char *vA )
{
    printf("A: %s\n", vA); // line 20

    return 'A';
}

int (*workB)( char *vB )
{
    printf("B: %s\n", vB); // line 27

    return 'B';
}

GCC complains:

test.c:20: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘{’ token
test.c:27: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘{’ token

I don't know what's wrong with it. Any comments will be highly appreciated.

Upvotes: 0

Views: 203

Answers (2)

Varad
Varad

Reputation: 145

When you write int (*workA) ( char *vA ), it means that workA is a pointer to a function that returns an int. workA is not a function.

Removing the parentheses around *workA and simply writing int (*workA) ( char *vA ) makes workA a function returning a pointer to an int, as required.

The same goes for workB.

You can use this great program called cdecl to ease things up.

Upvotes: 0

K Scott Piel
K Scott Piel

Reputation: 4380

workA and workB are pointers to two functions. You need to declare actual functions that will do the work, then assign them to your two pointers before you call them...

#include <stdio.h>

int (*workA) ( char *vA );
int (*workB) ( char *vB );

int workAFunction( char *vA )
{
    printf("A: %s\n", vA); // line 20

    return 'A';
}

int workBFunction( char *vB )
{
    printf("B: %s\n", vB); // line 27

    return 'B';
}

int main( int argc, char * argv[] )
{
    char *strA = "Hello.";
    char *strB = "Bonjour.";

    workA = workAFunction;
    workB = workBFunction;

    int a = workA(strA);
    int b = workB(strB);

    printf("Return value of A = %d, B = %d.\n", a, b);

    return 0;
}

Upvotes: 2

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