Using std::format with float or double based std::chrono::time_point causes error: invalid operands to binary expression

[HirthammerAllTerra]

Consider the following code snippet:

using Representation = double;
using Duration       = std::chrono::duration<Representation>;
using Clock          = std::chrono::system_clock;
using TimePoint      = std::chrono::time_point<Clock, Duration>;

TimePoint tp = {};

std::string time_string = std::format("{:%d.%m.%Y %H:%M:%S}", tp);

This results in the compile error:

error: invalid operands to binary expression ('basic_ostringstream<char>' and 'const std::chrono::time_point<std::chrono::system_clock, std::chrono::duration<double>>')
                  __os << __t;
                  ~~~~ ^  ~~~

If you change the type def Representation to an integer or unsigned integer type, the code compiles.

System Info:

OS: Ubuntu 22.04 LTS
Clang-Version: 15.0.7

Here is a link with the code that produces the error at Compiler Explorer. The error is still present in the newest available Clang version (17.0.1) at Compiler explorer.

[jwakely]

This is a bug in libstdc++ headers, not Clang. This should be closed.

You need to be aware that Clang on Compiler Explorer uses libstdc++ unless you use -stdlib=libc++

[HirthammerAllTerra]

This is a bug in libstdc++ headers, not Clang. This should be closed.

You need to be aware that Clang on Compiler Explorer uses libstdc++ unless you use -stdlib=libc++

Thanks for clarifying this. I wasn't aware of it. For reference, here is the related bug report for libstdc++.

[jwakely]

compiler-explorer/compiler-explorer#3682 has a good explanation.

[mordante]

Thanks @jwakely