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Re: Undefined behavior due to 6.5.16.1p3


Dear Joseph,

On 03/10/2015 11:01 PM, Joseph Myers wrote:
and did "u.b.b2 = f (u.a);" instead of "u.b.b2 = u.a;", that would not be
undefined (see 6.8.6.4 and GCC PR 43784).
Thanks for the references, those are useful!

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.

Robbert


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