[Bug c++/62036] New: Braced-init-list issuing -Wsequence-point warning

[Bug c++/62036] New: Braced-init-list issuing -Wsequence-point warning

[dacamara.cameron at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62036

            Bug ID: 62036
           Summary: Braced-init-list issuing -Wsequence-point warning
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dacamara.cameron at gmail dot com

#include <algorithm>
#include <iostream>
#include <iterator>
#include <thread>

int main() {
    int arr[10];
    std::iota(std::begin(arr), std::end(arr), 1);
    using itr_t = decltype(std::begin(arr));

    // the function that will display each element
    auto f = [] (itr_t first, itr_t last) {while (first != last)
std::cout<<*(first++)<<' ';};

    // we have 3 threads so we need to figure out the ranges for each thread to
show
    int increment = std::distance(std::begin(arr), std::end(arr)) / 3;
    auto first    = std::begin(arr);
    auto to       = first + increment;
    auto last     = std::end(arr);
    std::thread threads[3] = {
        std::thread{f, first, to},
        std::thread{f, (first = to), (to += increment)},
        std::thread{f, (first = to), last} // go to last here to account for
odd array sizes
    };
    for (auto&& t : threads) t.join();
}


I'm getting the sequence point warning with this piece of code and when I
execute it the thread at threads[1] prints nothing whatsoever. This should be
well defined according to the standard (I'm using sec. 8.5.4.4 as reference).
The fact that gcc even issues the -Wsequence-point warning is indicative that
the standard isn't being followed.

[Bug c++/62036] Braced-init-list issuing -Wsequence-point warning

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62036

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
As pointed out at
http://stackoverflow.com/questions/25115189/optimization-bug-regarding-gcc-stdthread#comment39095137_25115189
(where you apparently copied this code from) there's a known bug which is fixed
in GCC 4.9, see PR51253

[Bug c++/62036] Braced-init-list issuing -Wsequence-point warning

[dacamara.cameron at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62036

--- Comment #2 from Cameron <dacamara.cameron at gmail dot com> ---
Welp looks like my friend got to it before I did. My bad. Carry on and good
work!

[Bug c++/62036] Braced-init-list issuing -Wsequence-point warning

[dacamara.cameron at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62036

Cameron <dacamara.cameron at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #3 from Cameron <dacamara.cameron at gmail dot com> ---
duplicate of bug 51253

*** This bug has been marked as a duplicate of bug 51253 ***