Projet_SETI_RISC-V/riscv-gnu-toolchain/newlib/winsup/cygwin/tzcode/README
2023-03-06 14:48:14 +01:00

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/*
How the code in this directory is supposed to work...
2020/05/22 Mark Geisert <mark@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. An empty namespace.h suffices for Cygwin.
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 leading 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. localtime.c.patched is generated by
winsup/cygwin/Makefile[.in] operating with localtime.c.patch.
..mark
*/