C++ PATCH: PR3989

[Gabriel Dos Reis]

Mark Mitchell <mark@codesourcery.com> writes:

| This patch fixes PR3989, a regression relative to GCC 3.0 in 
| GCC 3.0.1.

Thanks!

[...]

|   	  val = build (COMPOUND_EXPR, DECL_CONTEXT (fn), arg, to);
| + 	  /* Even though the assignment may not actually result in any
| + 	     code being generated, we do not want to warn about the
| + 	     assignment having no effect.  That would be confusing to
| + 	     users who may be performing the assignment as part of a
| + 	     generic algorithm, for example.
| + 	     
| + 	     Ideally, the notions of having side-effects and of being
| + 	     useless would be orthogonal.  */
| + 	  TREE_SIDE_EFFECTS (val) = 1;

I'm not acquainted with all the implications of TREE_SIDE_EFFECTS,
but can the above have a possible impact on (current) optimizations?
I'm asking in order to fill my ignorance.

-- Gaby
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