core dumped when run this simple D program.

[Fox]

import std.stdio;

class myClas_1 {
	int a;
}

void main() {
	myClas_1 c1;
	writeln(c1.a);
}


===================
what's wrong? dmd and gdc both can compile these code, but can't 
run either.
DMD64 D Compiler v2.109.1
gcc 14.2.1 20240824 (GCC)
fedora 41
thanks!