Conversion from double to string is locale-dependent if TOML_FLOATING_POINT_CHARCONV is 0

[traversaro]

Environment

Compiler:
Any compiler that does not support to_chars for double , i.e. for which TOML_FLOATING_POINT_CHARCONV is 0.

C++ standard mode (e.g. 17, 20, 'latest'):
17

Target arch (e.g. x64):
Not relevant.

Exceptions enabled:
Not relevant.

Relevant toml++ configuration customizations:
Not relevant.

Relevant compilation flags:
Not relevant.

Describe the bug

When TOML_FLOATING_POINT_CHARCONV std::ostringstream is used to convert a double to a string in https://github.com/marzer/tomlplusplus/blob/v1.1.0/include/toml++/toml_parser_impl.h#L153 . However, the imbue method is not called, so the default locale, that is the global C++ locale set in https://en.cppreference.com/w/cpp/locale/locale/global . If it is intended to have the same behavior independently from the value TOML_FLOATING_POINT_CHARCONV, I guess it is necessary to call ss.imbue(std::locale::classic()); after the ss object is declared. I did not checked other code paths if TOML_FLOATING_POINT_CHARCONV is set to 0, but it is possible that they are affected as well.

Additional information

Related issues:

• URDF Parsers' code is implicitly assuming that "C" locale is set robotology/idyntree#288
• Use stringstream instead of stod to work around locale issues. ros/urdfdom_headers#42

cc @S-Dafarra @GiulioRomualdi

[marzer]

Oh, thanks for bringing this to my attention @traversaro!

[marzer]

@traversaro I've implemented a fix locally but in testing some additional locale machinery I uncovered a few other related issues, which I'll fix tomorrow before pushing anything.

[marzer]

@traversaro The fix for this is live now. Solving this forced me to learn about locales on unix and to add different locales to my CI pipeline, so any locale-based regressions should be caught in future.

[traversaro]

Thanks a lot. I reported these kind of locale-related bugs to several open source projects over the years, but I never saw something as complete as the testing infrastructure that you set up!