| Issue |
151521
|
| Summary |
Clang front-end crash on compiling lambda
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
olivermadge
|
The following code causes clang-19 to crash with the error `clang++-19: error: clang frontend command failed with exit code 139 (use -v to see invocation)`:
```
#include <utility>
#include <cstring>
#include <print>
template <typename TypeTuple>
auto count_types() {
return []<size_t... Idx>(std::index_sequence<Idx...>) {
return ([](std::tuple_element_t<Idx, TypeTuple> base) {return base;}(1) + ...);
}(std::make_index_sequence<std::tuple_size_v<TypeTuple>>{});
}
int main() {
std::println("{}", count_types<std::tuple<int>>());
std::println("{}", count_types<std::tuple<int, char>>());
}
```
Interestingly, if I introduce an additional intermediate lambda to extract Idx, it compiles without error:
```
#include <utility>
#include <cstring>
#include <print>
template <typename TypeTuple>
auto count_types() {
return []<size_t... Idx>(std::index_sequence<Idx...>) {
return ([]<size_t Index>(std::integral_constant<size_t, Index>) {
return [](std::tuple_element_t<Index, TypeTuple> base) {return base;}(1);
}(std::integral_constant<size_t, Idx>()) + ...);
}(std::make_index_sequence<std::tuple_size_v<TypeTuple>>{});
}
int main() {
std::println("{}", count_types<std::tuple<int>>());
std::println("{}", count_types<std::tuple<int, char>>());
}
```
Clang-19 from Arch Linux (version 19.1.7 on x86-64) invoked as `clang++-19 -emit-llvm -Xclang -disable-llvm-passes --std=c++20 clang_bug.cpp -c -o clang`
The same code compiles and runs with the expected result on clang++-20, g++-14 and g++-15
[clang_bug-86f8f9.cpp.log](https://github.com/user-attachments/files/21531707/clang_bug-86f8f9.cpp.log)
[clang_bug-86f8f9.sh.log](https://github.com/user-attachments/files/21531708/clang_bug-86f8f9.sh.log)
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