On 2015-03-11 14:27:25 +0100, Robbert Krebbers wrote:
> But what about "long long" on 32 bits machines. For example:
>
> union {
> long long a;
> struct { char b1; long long b2; } b;
> } u;
>
> Will GCC perform similar optimizations as for the case of big structs? I
> tried to play around with long long in Martin's example, but failed to
> trigger "unexpected" behaviors in GCC.
I've not tried, but how about something like:
struct S { long a, b, c, d; };
union U {
struct S a;
struct { char b1; struct S b2; } b;
};
u.b.b2 = u.a;
or: u.a = u.b.b2;
IMHO, struct S should be large enough to avoid using registers as
a temporary area (just in case...).
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