https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71007
Eric Gallager changed:
What|Removed |Added
Keywords||compile-time-hog,
||diagnostic
Status|UNCONFIRMED |NEW
Last reconfirmed||2017-08-21
CC||egallager at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #2 from Eric Gallager ---
(In reply to Johannes Schaub from comment #0)
> The following is supposed to tell the user that char[0] is an invalid type,
> during diagnostic printing. But instead, it infinitely recurses up to
> SIZE_MAX or something during printing the diagnostic message, eventually
> crashing
>
>#include
>#include
>
>template
>auto ignore_n(std::integer_sequence) {
> return std::make_tuple((I, std::ignore)...);
>}
>
>template
>auto function(Ts... ts)
> -> decltype((std::tuple_cat(
>
> ignore_n(std::make_index_sequence
> ()),
> std::tuple()) = std::forward_as_tuple(ts...)),
> void())
>{
>
>}
>
>int main() {
> function(2);
> function(1, 2, 3);
>}
>
This un-reduced version was taking forever to compile, so I had to kill it
before it could crash:
$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic -time -ftime-report 71007.cc
71007.cc: In function ‘int main()’:
71007.cc:19:12: error: no matching function for call to ‘function(int)’
function(2);
^
71007.cc:10:6: note: candidate: ‘template decltype
((std::tuple_cat(ignore_n(typename std::_Make_integer_sequence::__type>::make_index_sequence()), std::tuple())=
std::forward_as_tuple(function::ts ...), void())) function(Ts ...)’
auto function(Ts... ts)
^~~~
71007.cc:10:6: note: template argument deduction/substitution failed:
71007.cc: In substitution of ‘template decltype
((std::tuple_cat(ignore_n(typename std::_Make_integer_sequence::__type>::make_index_sequence()), std::tuple())=
std::forward_as_tuple(function::ts ...), void())) function(Ts ...) [with Ts =
{int}]’:
71007.cc:19:12: required from here
71007.cc:12:42: warning: ISO C++ forbids zero-size array [-Wpedantic]
ignore_n(std::make_index_sequence
()),
^~
^C
$
(In reply to Johannes Schaub from comment #1)
> Sorry, forgot to actually add the code of the reduced testcase:
>
>template
>void f(char(&)[N])
>{ }
>
>int main() {
> char x[1];
> f(x);
>}
Confirmed:
$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic 71007_reduced.cc
71007_reduced.cc: In function ‘int main()’:
71007_reduced.cc:7:4: error: no matching function for call to ‘f(char [1])’
f(x);
^
71007_reduced.cc:2:6: note: candidate: ‘template void f(char
(&)[N])’
void f(char(&)[N])
^
71007_reduced.cc:2:6: note: template argument deduction/substitution failed:
71007_reduced.cc:1:17: warning: ISO C++ forbids zero-size array [-Wpedantic]
template
^~~~
$
Weird that the underlining here points to the typename before T rather than the
actual array size.
