alignmentof

#include <cstdio>

template<typename T>
size_t __alignmentof() {
	struct padded { char padding; T value; };
	return (size_t)(&(((padded*)0)->value)); //offsetof
}
#define alignmentof(T) __alignmentof<T>()

#define p(T) printf("for %s: size=%d, alignment=%d\n", #T, (int)sizeof(T), (int)alignmentof(T))
int main(int argc, char** argv) {
	p(char);
	p(short);
	p(int);
	p(long long);
	p(float);
	p(int[3]);
}

output

for char: size=1, alignment=1
for short: size=2, alignment=2
for int: size=4, alignment=4
for long long: size=8, alignment=8
for float: size=4, alignment=4
for int[3]: size=12, alignment=4