Add noexcept to make the "no throw" part of the contract and thus understandable also for the compiler :-)

How can I (or the compiler) be sure that no other exceptions (e.g. std::out_of_range) are thrown?

There is really no shortcut here AFAIK: reading + reasoning would be required :-)

Do you see any places where e.g. std::out_of_range could be thrown that is reachable from format? Beyond the already handled format_error.

The contract of tinyformat is that format_error is the only exception thrown?

I think the point of adding "noexcept" isn't so much because you know a function won't throw; it's that you know that exceptions thrown anyway can be regarded as fatal errors.

Stroustrup and Sutter:

E.12: Use noexcept when exiting a function because of a throw is impossible or unacceptable

F.6: If your function may not throw, declare it noexcept

format_no_throw seems like an ideal candidate for noexcept :-)

I see, so it is equivalent to std::terminate. I think I will leave that for later, as I am not sure that immediate termination is better than offering the gui or daemon to catch the exception

I think it is unwise to use function naming (format_no_throw) which gives the caller the impression that the contract is that the function cannot throw if we're not willing to back that with a noexcept guarantee.

I think we should either 1.) handle any non-fatal exception within format_no_throw and mark it noexcept, or 2.) remove the _no_throw suffix.

Maybe add a comment like This function wraps format() to return error messages instead of throwing format_error. All other format() exceptions are thrown away.

Added a comment

I suggest making LogPrintf noexcept, but before doing so note that the following call chain is triggered here (also before this PR):

• LogPrintStr → LogTimestampStr → FormatISO8601DateTime → strprintf

Generally strprintf may throw tinyformat::format_error.

In the case of the call FormatISO8601DateTime I don't think that is possible since the format string is well formed. However, that is not understood by the compiler which currently must assume that FormatISO8601DateTime can throw.

I suggest handling the (non-reachable) tinyformat::format_error explicitly in FormatISO8601DateTime and then making that function noexcept too. (Should be done also for its companion FormatISO8601Date).

So in summary my suggestion is to:

• Handle tinyformat::format_error in FormatISO8601DateTime and FormatISO8601Date
• Add noexcept to FormatISO8601DateTime, FormatISO8601Date and LogPrintf