Declaration of pointers in c

Question

I am using gcc 4.8.1 and I am unable to understand output of following program.

#include<stdio.h>
int main()
{

    char* a, b, c;
    int* d, e, f;
    float* g, h, i;
    printf("Size of a %zu and b %zu and c %zu \n", sizeof(a), sizeof(b), sizeof(c));
    printf("Size of d %zu and e %zu and f %zu and int is %zu \n", sizeof(d), sizeof(e), sizeof(f), sizeof(int*));
    printf("Size of g %zu and h %zu and i %zu and float is %zu \n", sizeof(g), sizeof(h), sizeof(i), sizeof(float));
    return 0;
}

Output is

Size of a 4 and b 1 and c 1
Size of d 4 and e 4 and f 4 and int is 4
Size of g 4 and h 4 and i 4 and float is 4

My question is why b and c are not char* type whereas same is possible in case of int and float. I want to know about how C grammar splits declarations.

Answer 1

In a declaration like

char* a, b, c;

Only the type char is used for all variables, not whether it is a pointer (* symbol). When used like that this (equivalent) syntax makes it more clear:

char *a, b, c;

To define 3 pointers:

char *a, *b, *c;

Or in cases where multiple pointers to char are often used, maybe do a typedef:

typedef char* char_buffer;
char_buffer a, b, c;

Answer 2

The problem is that you are using a bad style of declarations

These declarations

char* a, b, c;
int* d, e, f;
float* g, h, i;

are equivalent to

char* a;
char b, c;
int* d;
int e, f;
float* g;
float  h, i;

sizeof an object of type char is equal to 1 while sizeof( char * ) in your system is equal to 4. So you get correct output

Size of a 4 and b 1 and c 1

As sizeof( int ) and sizeof( float ) in your system is equal to 4 then you get output

Size of d 4 and e 4 and f 4 and int is 4
Size of g 4 and h 4 and i 4 and float is 4

I said that you use bad style of programming because the declarations you are using like this

char* a, b, c;

do not consistent with the C grammar. The C grammar splits declarations in declaration specifiers (for the statement above it is keyword char) and declarators (in statement above they are *a, b, and c ). So you should follow the C grammar. In this case your code will be more clear.

char *a, b, c;

(Compare for example

char unsigned* c;

and

char unsigned *c;

What declaration is more clear?)

Do not forget that your code can read programmers that for example do not know C but know C#. In this case they will be simply confused. They will consider the declarations in the wrong way as you considered them in your post.