[Bug c++/115052] New: rejected lambda while capturing a constexpr array

[Bug c++/115052] New: rejected lambda while capturing a constexpr array

[franckbehaghel_gcc at protonmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115052

            Bug ID: 115052
           Summary: rejected lambda while capturing a constexpr array
           Product: gcc
           Version: 14.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: franckbehaghel_gcc at protonmail dot com
  Target Milestone: ---

The following code is fine :

constexpr int a1[] = { 1, 2};
int f_lambda_capturing_case1(int id)
{
   return [] (int i) { return a1[i];}(id);
}



But this one is rejected :

int f_lambda_capturing_case2(int id)
{
   constexpr int a2[] = { 1, 2};
   return [] (int i) { return a2[i];}(id);
}



In lambda function:
<source>:12:31: error: 'a2' is not captured
   12 |    return [] (int i) { return a2[i];}(id);
      |                               ^~
<source>:12:12: note: the lambda has no capture-default
   12 |    return [] (int i) { return a2[i];}(id);
      |            ^
<source>:11:18: note: 'constexpr const int a2 [2]' declared here
   11 |    constexpr int a2[] = { 1, 2};



The second case seems also valid as it is just a change of scope.
Moreover it is accepted by clang.

regards,

[Bug c++/115052] rejected lambda while capturing a constexpr array

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115052

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
MSVC rejects it also with the similar error message as GCC:
<source>(5): error C3493: 'a2' cannot be implicitly captured because no default
capture mode has been specified


While EDG accepts it.

So it is 2 compilers that accept it and 2 compilers that reject it.