I did: > 2026-10-01 Bruno Haible <[email protected]> > > tzsanitize: New module.
While the intent was that this module be only implicitly imported by packages, it turns out that packages have a real need to use it explicitly. Namely, some applications need to call tzsanitize() during their initialization. Seen with GNU clisp when linked against MSVCRT. Not reproducible with GNU clisp linked against UCRT; I don't know why. 2026-10-02 Bruno Haible <[email protected]> tzsanitize: Add more comments. * lib/tzsanitize.h: Explain why applications need to call tzsanitize() explicitly. diff --git a/lib/tzsanitize.h b/lib/tzsanitize.h index c7c50d1a55..9f8ef769c7 100644 --- a/lib/tzsanitize.h +++ b/lib/tzsanitize.h @@ -47,6 +47,31 @@ extern "C" { neutralize it or not, since these values occur only when a Cygwin user has set TZ explicitly; this case is 1. rare and 2. under the user's responsibility. */ + +/* Applications need to make sure that tzsanitize() gets invoked (at least + once) *before* the first invocation of __tzset() in the Microsoft runtime + library. This is because + - __tzset looks at the value of the environment variable "TZ". + - The first invocation of __tzset sets some cached variables. + Further invocations of __tzset do nothing. + + The gnulib overrides of + localtime, mktime, tzset, strftime, wcsftime, ctime + do call tzsanitize(); therefore no explicit tzsanitize() invocations are + needed in simple programs. But some other functions do call __tzset() + implicitly: + - In the Microsoft runtime library: + stat = _stat64, fstat = _fstat64. + MSVCRT: _stat64, _fstat64 -> __loctotime64_t -> __tzset. + UCRT: _fstat64 -> common_fstat -> common_stat_handle_file_opened + -> convert_large_integer_time_to_time_t + -> loctotime -> common_loctotime_t -> __tzset. + - In GNU libintl: + [d]gettext -> dcigettext -> _nl_find_domain -> _nl_load_domain -> fstat. + + Therefore programs that are linked to such libraries need to call + tzsanitize() early during their initialization. */ + extern void tzsanitize (void); #endif
