Character Types and Arrays

There are a couple of differences in the way that ANSI C and C++ treat character constants and arrays of characters. One of these has to do with the type of a character constant. For example:

#include

int main()
{
printf("%d\n", sizeof('x'));

return 0;
}

If this program is compiled as ANSI C, then the value printed will be sizeof(int), typically 2 on PCs and 4 on workstations. If the program is treated as C++, then the printed value will be sizeof(char), defined by the draft ANSI/ISO standard to be 1. So the type of a char constant in C is int, whereas the type in C++ is char. Note that it's possible to have sizeof(char) == sizeof(int) for a given machine architecture, though not very likely.

Another difference is illustrated by this example:

#include

char buf[5] = "abcde";

int main()
{
printf("%s\n", buf);

return 0;
}

This is legal C, but invalid C++. The string literal requires a trailing \0 terminator, and there is not enough room in the character array for it. This is valid C, but you access the resulting array at your own risk. Without the terminating null character, a function like printf() may not work correctly, and the program may not even terminate.