https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116694
Bug ID: 116694
Summary: -Ftemplate-depth = parameter does not match the actual
number of instantiations
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: polarlinda6 at 163 dot com
Target Milestone: ---
Version: x86-64 gcc 14.2.1
command-line parameter: -ftemplate-depth=52 -std=c++20
Link: https://godbolt.org/z/rnn35nsac
PS: The code compiles successfully and clang.
( MSVC does not provide a parameter for the template instantiation depth and
cannot be tested )
```cpp
#include <utility>
template<auto s, auto... S>
struct A {
constexpr static auto value = A<S...>::value;
};
template<auto s>
struct A<s> {
constexpr static auto value = s;
};
template<auto... S>
auto func(std::index_sequence<S...>) {
return A<S...>::value;
}
auto main() -> int { auto s = func(std::make_index_sequence<50>{}); }
```
#### error message:
<source>: In instantiation of 'struct A<25, 26, 27, 28, 29, 30, 31, 32, 33, 34,
35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49>':
<source>:5:42: required from 'constexpr const auto A<24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49>::value'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:25: required from 'struct A<24, 25, 26, 27, 28, 29, 30, 31, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49>'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:42: required from 'constexpr const auto A<23, 24, 25, 26, 27, 28,
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49>::value'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:25: required from 'struct A<23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49>'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:42: required from 'constexpr const auto A<22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
48, 49>::value'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:25: [ skipping 41 instantiation contexts, use
-ftemplate-backtrace-limit=0 to disable ]
<source>:5:42: required from 'constexpr const auto A<1, 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49>::value'
<source>:5:25: required from 'struct A<1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49>'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:42: required from 'constexpr const auto A<0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
48, 49>::value'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:5:25: required from 'struct A<0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49>'
5 | constexpr static auto value = A<S...>::value;
| ^~~~~
<source>:14:19: required from 'auto func(std::index_sequence<S ...>) [with
auto ...S = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49}]'
14 | return A<S...>::value;
| ^~~~~
<source>:17:35: required from here
17 | auto main() -> int { auto s = func(std::make_index_sequence<50>{}); }
| ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:5:25: fatal error: template instantiation depth exceeds maximum of 52
(use '-ftemplate-depth=' to increase the maximum)
5 | constexpr static auto value = A<S...>::value;
|
