7.3.9 sizeof( ) Is an Unsigned long

In the LP64 data-type model, sizeof() has the effective type of an unsigned long. Occasionally, sizeof() is passed to a function expecting an argument of type int, or assigned or cast to an integer. In some cases, this truncation causes loss of data.

long a[50];
unsigned char size = sizeof (a);

%
warning: 64-bit constant truncated to 8 bits by assignment
warning: initializer does not fit or is out of range: 0x190