[Bug c++/20280] [4.0/4.1 regression] ICE in create_tmp_var, at gimplify.c:368

[mark at codesourcery dot com]

------- Additional Comments From mark at codesourcery dot com  2005-03-04 01:36 -------
Subject: Re: [PR c++/20280] hoist indirect_ref out of addressable cond_exprs

Alexandre Oliva wrote:
\
> I went ahead and verified that I didn't break bit-field lvalues in
> conditional expressions (my first attempt did), but I was surprised to
> find out that the calls to h() pass.  I understand why they do (we
> create a temporary and bind to that), but I'm not sure this is correct
> behavior.  Opinions?

> +  // Hmm...  I don't think these should be accepted.  The conditional
> +  // expressions are lvalues for sure, and 8.5.3/5 exempts lvalues
> +  // that are bit-fields, but not lvalues that are conditional
> +  // expressions involving bit-fields.
> +  h (b ? x.i : x.j);
> +  h (b ? x.i : x.k);
> +  h (b ? x.j : x.k);

That's legal because "h" takes a "const &", which permits the compiler 
to create a temporary.  If it takes a non-const reference, you should 
get an error.

And, I think these kinds of transformations (if necessary) should be 
done in a langhook during gimplification, not at COND_EXPR-creation 
time.  We really want the C++ front-end's data structures to be an 
accurate mirror of the input program for as long as possible.



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20280