https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87559
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Any gcc bugs seem to be fixed in current trunk. As a single testcase:
extern "C" int puts(const char*);
constexpr char top_doc[] = "";
void f1() {
constexpr auto& doc = top_doc;
[](int) { puts(doc); }(1); // should compile
[](auto) { puts(doc); }(2); // should compile
}
void f2() {
constexpr char doc[] = "";
[](int) { puts(doc); }(3); // should fail
[](auto) { puts(doc); }(4); // should fail
}
GCC 7 gets three of the four cases wrong, incorrectly rejecting the second, and
incorrectly accepting the third and fourth:
87559.cc: In lambda function:
87559.cc:8:19: error: 'doc' is not captured
[](auto) { puts(doc); }(2); // should compile
^~~
87559.cc:8:4: note: the lambda has no capture-default
[](auto) { puts(doc); }(2); // should compile
^
87559.cc:6:19: note: 'constexpr const char (& doc)[1]' declared here
constexpr auto& doc = top_doc;
^~~
But GCC 8 gets them all right, compiling the first two and rejecting the last
two:
87559.cc: In lambda function:
87559.cc:13:18: error: 'doc' is not captured
[](int) { puts(doc); }(3); // should fail
^~~
87559.cc:13:4: note: the lambda has no capture-default
[](int) { puts(doc); }(3); // should fail
^
87559.cc:12:18: note: 'constexpr const char doc [1]' declared here
constexpr char doc[] = "";
^~~
87559.cc: In instantiation of 'f2()::<lambda(auto:2)> [with auto:2 = int]':
87559.cc:14:28: required from here
87559.cc:14:19: error: 'doc' is not captured
[](auto) { puts(doc); }(4); // should fail
^~~
87559.cc:14:4: note: the lambda has no capture-default
[](auto) { puts(doc); }(4); // should fail
^
87559.cc:12:18: note: 'constexpr const char doc [1]' declared here
constexpr char doc[] = "";
^~~
