| Issue |
180319
|
| Summary |
clang: recusive lambdas in templates can segfault by exausting stack
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
ribbon-otter
|
Compiling the following code causes a stack-overflow
```c++
struct foo_tag {};
template<class T> struct foo {
using tag = foo_tag;
T run;
};
template<class T> concept isFoo = requires(T a) {a.run();};
//function to construct very complex type with lambda
template<int i, class T> auto complexify(T a) requires isFoo<T> {
if constexpr (i > 0) {
return complexify<i-1>(foo{ [a]{
return 1+a.run();
}});
} else return a;
}
//base case
template<int i> auto complexify(int a) {
return complexify<i-1>(foo{ [a]{
return a;
}});
}
int main() {
auto a = complexify<389>(1);
}
// vim: ts=2 sw=2
```
Output that the main version of clang outputs:
[output.txt](https://github.com/user-attachments/files/25141859/output.txt)
and the files it wishes me to attach:
[clang-bug-c2e6e3.sh](https://github.com/user-attachments/files/25141857/clang-bug-c2e6e3.sh)
[clang-bug-c2e6e3.cpp](https://github.com/user-attachments/files/25141858/clang-bug-c2e6e3.cpp)
by adjusting `complexify<398>(t)` to be a slightly smaller (for example, `381` on my machine + build), I get a warning about the stack being nearly exhausted.
```
clang-bug.cpp:3:26: warning: stack nearly exhausted; compilation time may suffer, and crashes due to stack overflow
are likely [-Wstack-exhausted]
```
g++ compiles it without issue. (though it has a related bug ([Bug 120124](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120124)) where it crashes there is an error message that involves this; which is how I found this clang bug by accident)
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
