Bug 2821 – struct alignment inconsistent with C for { int, long }

I couldn't find it in the spec right now, but as far as I remember D and C structs are supposed to be aligned identically when the same types are used. struct S { int i; long l; } In C (using gcc 4.1.2), the S.l.offsetof is 4 and the total size is 12. With dmd the offsetof is 8 and the total size is 16. Test code: -- D code import std.stdio; struct S { int i; long l; } void main() { writefln("%d %d", S.sizeof, S.l.offsetof); } -- C code #include <stdio.h> struct S { int i; long long l; }; int main() { struct S s; printf("%d %d\n", sizeof(s), (void*)&s.l - (void*)&s); return 1; } --

Have you tried DMC and GDC to compare? One would expect GDC to do the same as GCC, and DMD to do the same as DMC. But how does each decide what alignment to default to in the first place?

DMD on Win32 should obviously match DMC, but DMD on other platforms should match the companion C compiler there, which is GCC. GCC on x86-32 aligns int64 to 4 bytes (at least on Linux). There was a similar issue with double that was fixed in 1.042: http://d.puremagic.com/issues/show_bug.cgi?id=2692

Fixed dmd 1.045 and 2.030