--- winsup/cygwin/tzcode/README | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 winsup/cygwin/tzcode/README
diff --git a/winsup/cygwin/tzcode/README b/winsup/cygwin/tzcode/README new file mode 100644 index 000000000..a200502ea --- /dev/null +++ b/winsup/cygwin/tzcode/README @@ -0,0 +1,37 @@ +/* + How the code in this directory is supposed to work... + 2020/05/13 Mark Geisert <m...@maxrnd.com> + + localtime.cc is the Cygwin-specific module that is compiled into + the Cygwin DLL when the latter is built. It's just a wrapper that + #defines a bunch of stuff then #includes localtime.c. + + localtime.c, at any point in time, is a reasonably recent version + of /src/lib/libc/time/localtime.c from NetBSD. The same goes for + private.h and tzfile.h. OTOH namespace.h implements something on + NetBSD that is not provided on Cygwin, so it's empty here. + + The idea is that in the future, one just needs to bring over newer + versions of localtime.c, private.h, and/or tzfile.h from NetBSD as + they become available. + + With luck, you can drop those files into this directory and they + can be immediately used to build a newer Cygwin DLL that has the + newer NetBSD functionality. Without luck, you'll have to tweak the + wrapper localtime.cc. In the worst case, some other strategy will + need to be figured out, such as manually pulling out the parts of + the NetBSD code Cygwin needs to build a stand-alone localtime.cc. + + Re tz_posixrules.h: The data elements can be generated from + /usr/share/zoneinfo/posixrules in any version of Cygwin's tzdata + package. Instructions are in the comment heading tz_posixrules.h. + + Addendum: + Implementation of the strategy above has uncovered a small number + of NetBSD-isms in localtime.c that cannot be worked around with + preprocessor tricks. So there is another file localtime.c.patched + that holds just these adjustments for Cygwin, and it's this file + that localtime.cc #includes. + + ..mark +*/ -- 2.21.0
