// Array LENGTH - count number of array elements with error generation in case of improper use

#include <stdio.h>
#include <stddef.h>

#ifdef __augmented // @C - augmented version of C programming language
  #define LENGTH length // In @C it is defined internal as length
#endif

#ifndef LENGTH
  #ifdef _MSC_VER // MSVC-compatible version
    #define LENGTH(A) (sizeof(A) / sizeof((A)[0]) + \
      sizeof(char[1 - 2*!!(sizeof(A) == sizeof(void*))]) * 0)
  #endif
#endif

#ifndef LENGTH
  #if defined(__GNUC__) || defined(__clang__) // GCC/Clang typeof-based macro (compiler-specific)
  #define LENGTH(A) ( sizeof(A) / sizeof((A)[0]) + \
    sizeof(typeof(int[1 - 2*!!__builtin_types_compatible_p(typeof(A), typeof(&(A)[0]))])) * 0 )
    //sizeof(struct{int:-(__builtin_types_compatible_p(typeof(A), typeof(&(A)[0])));}))// Variant
  #endif
#endif

#ifndef LENGTH
  #ifdef __STDC_VERSION__
    #if __STDC_VERSION__ >= 201112L
        #define LENGTH(A) (_Generic((A) + 0, default: sizeof(A) / sizeof(*(A)) ))
    #else
      #if __STDC_VERSION__ >= 199901L // C99+ compound literal approach
        #define LENGTH(A) (sizeof(A) / sizeof((A)[0]) + \
          0 * sizeof(struct{char c[sizeof(A) == sizeof(void*) ? -1 : 1];}) )
      #endif
    #endif
  #endif
#endif


#ifndef LENGTH
  #define LENGTH(A) (sizeof(A) / sizeof((A)[0])) // A pointer is seen as an array with length 1!
#endif

int staticArray[] = {1, 2, 3, 4, 5}; // static array with known size at compile-time
int *Pointer = (int *)staticArray; // pointer (could be dynamic or alias to static)

void Test(int fixedArrayParam[5],   // declared as fixed-size but decays to pointer
          int inferredArrayParam[], // array syntax, but decays to pointer
          int *pointerParam,        // explicit pointer
          int Length)               // actual length for dynamically-sized stack array
{
  int stackArray[Length]; // Variable Length Array (VLA) on the stack

  printf("LENGTH(staticArray) = %d\n", LENGTH(staticArray)); // correct usage
  //printf("LENGTH(Pointer) = %d\n", LENGTH(Pointer)); // incorrect usage
  //printf("LENGTH(fixedArrayParam) = %d\n", LENGTH(fixedArrayParam)); // incorrect usage
  //printf("LENGTH(inferredArrayParam) = %d\n", LENGTH(inferredArrayParam)); // incorrect usage
  //printf("LENGTH(pointerParam) = %d\n", LENGTH(pointerParam)); // incorrect usage
  printf("LENGTH(stackArray) = %d\n", LENGTH(stackArray)); // correct usage
}

int main(void)
{
  Test(staticArray, Pointer, Pointer, 10);
  return 0;
}

https://onecompiler.com/c/43sa5q7g9