https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98450
Bug ID: 98450
Summary: Inconsistent Wunused-variable warning for std::array
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: maic23 at live dot de
Target Milestone: ---
When using std::array in C++17 mode, -Wunused-variable behaves inconsistent:
$ cat /tmp/a.cpp
#include <array>
static constexpr std::array bay{9};
static constexpr std::array<int, 1> bax{9};
$ gcc -std=c++17 -Wall -S /tmp/a.cpp
/tmp/a.cpp:2:37: warning: ‘bay’ defined but not used [-Wunused-variable]
2 | static constexpr std::array bay{9};
| ^~~
Now, if the two lines are switched, there is no warning:
$ cat /tmp/b.cpp
#include <array>
static constexpr std::array<int, 1> bax{9};
static constexpr std::array bay{9};
$ gcc -std=c++17 -Wall -S /tmp/b.cpp
(no warning)
It makes it really hard to debug and fix this warning when it occurs only
sporadically.
The warning should probably not appear at all, because static const(expr)
variables are put in header files, but not used everywhere where the header
file is included in a cpp file.
