Bug: fmt::print(...) infinite recursion when using std::filesystem::path and fmt/ranges.h header is included

[odygrd]

Executing the following code will enter an infinite recursion and the program will crash

template <typename... Args>
auto capture(const Args&... args) {
return std::make_tuple(args...);
}

auto print_message = [](const auto&... args) {
fmt::print(args...);
};

int main()
{
std::filesystem::path ph {"test_path"};

auto args = capture("{}", ph);

std::apply(print_message, args);
}

[vitaut]

I wasn't able to make your example compile: https://godbolt.org/z/FKJcEH. Please provide more details including the compiler version and {fmt} library version.

[odygrd]

I see it doesn't compile.
I am using gcc 9.1 and the libfmt version was very recent from master last updated about ~15/20 days ago but I don't have the exact commit hash.
Maybe you've changed something within that period

[odygrd]

I made it compile on godbolt

https://godbolt.org/z/g1c6Q-

When fmt/ranges.h is not included the program runs fine.

If I #include fmt/ranges.h it will crash

I get ~94000 lines of stack so it is hard to copy paste here but it looks like this

[vitaut]

The problem is that std::filesystem::path looks like a range because it has begin() and end() which enables formatter specialization for ranges. However the latter should really be disabled because path is an infinitely deep range of itself 🤦‍♂️ (corrected: it has nothing to do with conversion to std::string, just poor design of the path API).

[vitaut]

Fixed in b2d4ca1. Thanks for reporting!