See also: https://quuxplusone.github.io/blog/2018/08/11/the-auto-macro/

On Mon, Dec 12, 2022 at 1:11 PM Jason C via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> It is unclear to me what these proposals (both this new one and the
> `scope_*` proposals) add that is not already trivially possible with code
> in scoped object destructors.
>
> Here are three of many other straightforward strategies. All may be fully
> contained in the function they are in, even #3, if desired:
> https://godbolt.org/z/9fWKhecrG
>
> Most notably, imo:
>
> struct generic_cleanup {
> explicit generic_cleanup (function<void()> cleanup) : cleanup(cleanup)
> { }
> ~generic_cleanup () { cleanup(); }
> private:
> function<void()> cleanup;
> };
>
> void oneScopedCleanupStrategy () {
>
> // local vars must be declared before cleanup is declared, of course:
> int localvar;
>
> // fairly convenient syntax:
> generic_cleanup cleanup([&] {
> cout << "strategy3: scope cleanup " << localvar << endl;
> });
>
> // modifications to local vars will be visible to cleanup ([&])
> localvar = 900;
>
> }
>
> Nothing would prevent `generic_cleanup` from maintaining a list of cleanup
> functions, either, if you'd like a more convenient syntax for building as
> you go.
>
> Full source follows signature.
>
> Jason
>
> #include <iostream>
> #include <string>
> #include <functional>
> #include <memory>
>
> using namespace std;
>
> void strategy1 () {
>
> struct scope_cleanup {
> ~scope_cleanup () {
> cout << "strategy1: scope cleanup " << endl;
> }
> } cleanup;
>
> int localvar = 123; // however; scope_cleanup cannot access localvar
>
> cout << "strategy1: entered" << endl;
>
> }
>
> void strategy2 () {
>
> struct scope_cleanup_with_data {
> int localvar;
> ~scope_cleanup_with_data () {
> cout << "strategy2: scope cleanup " << localvar << endl;
> }
> } context;
>
> context.localvar = 123; // this provides a strategy for maintaining
> data to be cleaned up
>
> cout << "strategy2: entered" << endl;
>
> }
>
> // a more general solution allowing a natural passing of local data
> struct generic_cleanup {
> explicit generic_cleanup (function<void()> cleanup) :
> cleanup(cleanup) { }
> ~generic_cleanup () { cleanup(); }
> private:
> function<void()> cleanup;
> };
>
> void strategy3 () {
>
> int localvar;
>
> generic_cleanup cleanup([&] {
> cout << "strategy3: scope cleanup " << localvar << endl;
> });
>
> cout << "strategy3: entered" << endl;
> localvar = 900;
>
> }
>
> int main () {
>
> const auto logcall = [](function<void()> callee, string name) {
> cout << name << ": calling" << endl;
> callee();
> cout << name << ": returned" << endl;
> };
>
> logcall(strategy1, "strategy1");
> logcall(strategy2, "strategy2");
> logcall(strategy3, "strategy3");
>
> }
>
>
>
>
>
>
>
> On Mon, Dec 12, 2022 at 10:00 AM Ville Voutilainen via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> On Mon, 12 Dec 2022 at 14:44, Jarrad Waterloo via Std-Proposals
>> <std-proposals_at_[hidden]> wrote:
>> >
>> > Not to be dense, does that mean the following is slated for 23 or 26?
>> >
>> > scope_exit
>> > scope_fail
>> > scope_success
>> > unique_resource
>>
>> Right now they're not being slated for either, because we don't (yet)
>> have the proposal to move any of them
>> into C++26. They certainly missed the train for C++23.
>> --
>> Std-Proposals mailing list
>> Std-Proposals_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>>
> --
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