Stupid macro tricks.

$ cat hw058.c

#include <stdio.h>

inline
static
int p(int x) {
  return x * x;
}

#define P(X) (X * X)
#define Q(X) ((X) * (X))

int main(int argc, char const * argv[]) {

  int i = 3;
  printf("%d %d ", i, P(i + 1));
  printf("%d %d ", i, P(i++));
  printf("%d %d ", i, P(++i));
  printf("%d ", i);
  putchar('\n');

  i = 3;
  printf("%d %d ", i, Q(i + 1));
  printf("%d %d ", i, Q(i++));
  printf("%d %d ", i, Q(++i));
  printf("%d ", i);
  putchar('\n');

  i = 3;
  printf("%d %d ", i, p(i + 1));
  printf("%d %d ", i, p(i++));
  printf("%d %d ", i, p(++i));
  printf("%d ", i);
  putchar('\n');

  return 0;
}

# Compiling with clang
# ##################################################################################
$ clang -Wall -std=gnu18 -o ../../bin/hw058c hw058.c
hw058.c:17:26: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, P(i++));
                   ~     ^
hw058.c:10:15: note: expanded from macro 'P'
#define P(X) (X * X)
              ^
hw058.c:18:25: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, P(++i));
                   ~    ^
hw058.c:10:15: note: expanded from macro 'P'
#define P(X) (X * X)
              ^
hw058.c:24:26: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, Q(i++));
                   ~     ^
hw058.c:11:16: note: expanded from macro 'Q'
#define Q(X) ((X) * (X))
               ^
hw058.c:25:25: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, Q(++i));
                   ~    ^
hw058.c:11:16: note: expanded from macro 'Q'
#define Q(X) ((X) * (X))
               ^
hw058.c:31:26: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, p(i++));
                   ~     ^
hw058.c:32:25: warning: unsequenced modification and access to 'i' [-Wunsequenced]
  printf("%d %d ", i, p(++i));
                   ~    ^
6 warnings generated.

# Compiling with gcc
# ##################################################################################
$ gcc-9 -Wall -std=gnu18 -o ../../bin/hw058g hw058.c
hw058.c: In function 'main':
hw058.c:17:26: warning: operation on 'i' may be undefined [-Wsequence-point]
   17 |   printf("%d %d ", i, P(i++));
      |                         ~^~
hw058.c:10:15: note: in definition of macro 'P'
   10 | #define P(X) (X * X)
      |               ^
hw058.c:17:26: warning: operation on 'i' may be undefined [-Wsequence-point]
   17 |   printf("%d %d ", i, P(i++));
      |                         ~^~
hw058.c:10:15: note: in definition of macro 'P'
   10 | #define P(X) (X * X)
      |               ^
hw058.c:18:25: warning: operation on 'i' may be undefined [-Wsequence-point]
   18 |   printf("%d %d ", i, P(++i));
      |                         ^~~
hw058.c:10:15: note: in definition of macro 'P'
   10 | #define P(X) (X * X)
      |               ^
hw058.c:18:25: warning: operation on 'i' may be undefined [-Wsequence-point]
   18 |   printf("%d %d ", i, P(++i));
      |                         ^~~
hw058.c:10:15: note: in definition of macro 'P'
   10 | #define P(X) (X * X)
      |               ^
hw058.c:24:26: warning: operation on 'i' may be undefined [-Wsequence-point]
   11 | #define Q(X) ((X) * (X))
      |               ~~~
......
   24 |   printf("%d %d ", i, Q(i++));
hw058.c:11:16: note: in definition of macro 'Q'
   11 | #define Q(X) ((X) * (X))
      |                ^
hw058.c:24:26: warning: operation on 'i' may be undefined [-Wsequence-point]
   11 | #define Q(X) ((X) * (X))
      |               ~~~
......
   24 |   printf("%d %d ", i, Q(i++));
hw058.c:11:16: note: in definition of macro 'Q'
   11 | #define Q(X) ((X) * (X))
      |                ^
hw058.c:25:25: warning: operation on 'i' may be undefined [-Wsequence-point]
   11 | #define Q(X) ((X) * (X))
      |               ~~~
......
   25 |   printf("%d %d ", i, Q(++i));
hw058.c:11:16: note: in definition of macro 'Q'
   11 | #define Q(X) ((X) * (X))
      |                ^
hw058.c:25:25: warning: operation on 'i' may be undefined [-Wsequence-point]
   11 | #define Q(X) ((X) * (X))
      |               ~~~
......
   25 |   printf("%d %d ", i, Q(++i));
hw058.c:11:16: note: in definition of macro 'Q'
   11 | #define Q(X) ((X) * (X))
      |                ^
hw058.c:31:26: warning: operation on 'i' may be undefined [-Wsequence-point]
   31 |   printf("%d %d ", i, p(i++));
      |                         ~^~
hw058.c:32:25: warning: operation on 'i' may be undefined [-Wsequence-point]
   32 |   printf("%d %d ", i, p(++i));
      |                         ^~~

# Running clang binary
# ##################################################################################
$ ../../bin/hw058c
3 7 3 12 5 42 7
3 16 3 12 5 42 7
3 16 3 9 4 25 5
# Running gcc binary
# ##################################################################################
$ ../../bin/hw058g
3 7 5 12 7 49 7
3 16 5 12 7 49 7
3 16 4 9 5 25 5