GCC: warning on unused return [duplicate]

Question

Problem statement

I use a return integer to propagate errors through my code. I would like gcc to provide me with a warning if I accidentally forget to propagate the error (i.e. when I forget to use the return integer).

Example

Consider this very simple example test.c:

// header
int test ( int a );

// function
int test ( int a )
{

  if ( a<0 ) return 1;

  return 0;
}

// main program
int main ( void )
{

  int a = -10;

  test(a);

  return 0;
} 

Expected behavior

$ gcc -Wunused-result main.c
Warning: main.c:19 ... unused return ...

or alternatively using Wall or Wextra or another option.

Needless to say, my compiler does not provide the warning with any of these options. One of my mistakes already took me frustratingly long to find...

Answer 1

// header
int test ( int a )  __attribute__ ((warn_unused_result));

// function
int test ( int a )
{

  if ( a<0 ) return 1;

  return 0;
}

// main program
int main ( void )
{

  int a = -10;

  test(a);

  return 0;
}

It should work now.