GUILE_INSTALL_LOCALE=1 breaks some of the robustness of non-locale-using programs, marring their stderr output if the environment's locale settings are faulty.
Suppose you have a program written in Guile Scheme that doesn't use any locale facilities. To be portable to the GUILE_INSTALL_LOCALE=1 situation (which the documentation threatens will become the default in Guile 2.2), it must be prepared to start up with some locale already selected, and reconfigure from there as required. Being a conscientious programmer, you are of course willing to add the (setlocale LC_ALL "C") and whatever other invocations are required to recover the non-locale state. But then this situation arises: $ LANG=wibble GUILE_INSTALL_LOCALE=1 guile-2.0 -c '(setlocale LC_ALL "C") (write "hi") (newline)' guile: warning: failed to install locale "hi" The warning shown goes to the program's stderr. It does not come from the program's setlocale call, which is succeeding and would signal a perfectly ordinary (catchable) exception if it failed. The warning comes from the implicit setlocale call triggered by GUILE_INSTALL_LOCALE=1, before the program gains control. As far as I can see, there is no way for the program to prevent the failing setlocale attempt or to muffle the warning. Or even to detect that this has happened. Guile should not be saying anything on the program's stderr. This is damaging the program's visible behaviour, and making it impossible to effectively port non-locale programs to new Guile versions. If Guile must attempt this implicit setlocale and continue to run the program if it fails, then it needs to keep quiet about the failure. This is no disadvantage to a program that actually wants to use the environmental locale, because the program is free to call (setlocale LC_ALL "") itself and handle its failure in whatever manner it finds appropriate. Indeed, any such program predating Guile 2.0 must already be performing that call itself, because the implicit setlocale didn't occur then. The same for any program portable to pre-2.0 Guiles. And on Guile 2.0+ such a program still really needs to perform the call itself, because it can't predict how GUILE_INSTALL_LOCALE will be set in the environment, so still can't rely on the implicit setlocale happening. However, if it is deemed to be essential that Guile attempt the implicit setlocale and gripe about its failure, then the message should not precede or otherwise mix with the actual program run. The message should be emitted *instead of* running the program, declaring the absolute incompatibility of the Guile framework with this environmental condition. -zefram
