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Re: [PATCH] Fix PR c++/70121 (premature folding of const var that was implicitly captured)
- From: Jason Merrill <jason at redhat dot com>
- To: Patrick Palka <patrick at parcs dot ath dot cx>, gcc-patches at gcc dot gnu dot org
- Date: Fri, 18 Mar 2016 11:14:41 -0400
- Subject: Re: [PATCH] Fix PR c++/70121 (premature folding of const var that was implicitly captured)
- Authentication-results: sourceware.org; auth=none
- References: <1457650689-16404-1-git-send-email-patrick at parcs dot ath dot cx>
On 03/10/2016 05:58 PM, Patrick Palka wrote:
This patch reverses the behavior of process_outer_var_ref, so that we
always implicitly capture a const variable if it's capturable, instead
of always trying to first fold it to a constant. This behavior however
is wrong too, and introduces a different but perhaps less important
regression: if we implicitly capture by value a const object that is not
actually odr-used within the body of the lambda, we may introduce a
redundant call to its copy/move constructor, see pr70121-2.C.
In general I'm disinclined to trade one bug for another, and I'm
skeptical that the different regression is less important; I imagine
that most uses of const variables will be for their constant value
rather than their address.