dereferencing -Wpointer-arith

[ghost]

@Hello,

dereferencing and pointer-arithmetic on void pointers is not permitted by the standard since sizeof(void) is undefined, moreover, Wimplicit-function-declaration, please declare your function prototypes or use extern, that's easy.

[yangzhang]

Hi I'm not very clear what you mean? could you give me an example?

[ghost]

@hello,

add this flag to your build script -Wpointer-arith

(flag which matters to many folks, especially when dealing with SIMD types and in a greater concern memory alignments and generic pointer arithmetics)

example

/** gcc test.c -Wall -Wpointer-arith **/
#include <stdio.h>

int main (int argc, char **argv)
{
  void * bar;
  void * foo;
  foo = bar + 1;
  return 0;
}
/**
test.c: In function ‘main’:
test.c:8: warning: pointer of type ‘void *’ used in arithmetic
**/

Wimplicit-function-declaration warning is triggered when there is a lack of function prototype declaration, K&R is dead.

example

/** gcc test.c -Wall **/
int main (int argc, char **argv)
{
    const char * bar = "hello";
    long l = strlen(bar);
    void * foo;
    foo = bar + 1;
    return 0;
}
/**
test.c: In function ‘main’:
test.c:4: warning: implicit declaration of function ‘strlen’
test.c:4: warning: incompatible implicit declaration of built-in function ‘strlen’
test.c:6: warning: assignment discards qualifiers from pointer target type
test.c:4: warning: unused variable ‘l’
**/

let me know,

Cheers!

[yangzhang]

thanks, I will try it!

[ghost]

ignorance is made of attempts, knowledge is made of acts.

Cheers.