A macro parameter that is used as an operand of a # or ## operator is not expanded prior to being used. The same parameter appearing elsewhere in the replacement text is expanded. If the macro parameter is itself subject to macro replacement, its use in mixed contexts within a macro replacement may not meet developer expectations.

Example

In the following non-compliant example, the macro parameter x is replaced with AA which is subject to further macro replacement when not used as the operand of ##.

#define AA             0xffff 
#define BB( x )        ( x ) + wow ## x     /* Non-compliant */

void f ( void ) 
{
  int32_t wowAA = 0;

  /* Expands as wowAA = ( 0xffff ) + wowAA; */ 
  wowAA = BB ( AA ); 
}

In the following compliant example, the macro parameter X is not subject to further macro replacement.

int32_t speed; 
int32_t speed_scale; 
int32_t scaled_speed;

#define SCALE( X ) ( ( X ) * X ## _scale )

/* expands to scaled_speed = ( ( speed ) * speed_scale ); */ 
scaled_speed = SCALE ( speed );