Bug 11151 – Undetected overlapping initialization

The union field U.a and U.y are overlapped but compiler doesn't detect the issue. import core.stdc.stdio : printf; union U { struct { align(1) long a; align(1) int b; } struct { align(1) int x; align(1) long y; } } void main() { pragma(msg, U.a.offsetof); // 0 pragma(msg, U.b.offsetof); // 8 pragma(msg, U.x.offsetof); // 0 pragma(msg, U.y.offsetof); // 4 U u = {a:1, y:2}; // overlapped initializing U.a and U.y printf("u.a = %lld\n", u.a); // 8589934593 , Wrong! printf("u.b = %d\n", u.b); // 0 printf("u.x = %d\n", u.x); // 1 printf("u.y = %lld\n", u.y); // 2 }

Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/cd6102367906c0a76f4ad56375e8bdf653321e0b fix Issue 11151 - Undetected overlapping initialization