Casting

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Casting#

Casts are written as (T)expr. Avoid casts where the language would convert implicitly; casts are reserved for genuinely changing representation.

Truncating a double to int.

double d = 3.7;
int    i = (int)d;           /* 3 (truncates) */

Casting through void *.

void  *vp = malloc(16);
char  *cp = (char*)vp;       /* explicit cast from void* */

Implicit integer promotions (the integer promotions and usual arithmetic conversions) silently widen and re-sign; the operator reads them carefully.

unsigned char a = 250;
signed   char b = -10;
if (a + b > 0) { /* a and b promote to int before adding */ }

References#

  • Primitives for the integer types affected by promotion.

  • Pointers for void * and the (T*) cast form.

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