Hi,
> On 23 Dec 2022, at 23:17, Jonathan Wakely <jwakely....@gmail.com> wrote:
>
> On Fri, 23 Dec 2022, 17:06 Iain Sandoe via Libstdc++, <libstd...@gcc.gnu.org>
> wrote:
> This is a patch for comment on the approach - tested on x86_64-darwi21
> thoughts?
> Iain
>
> --- 8< ---
>
> Testing on Darwin revealed that the GLIBCXX_ZONEINFO_DIR was not doing quite
> the right thing (we ended up with ${withval} in the config.h file).
>
> This patch proposes revising the behaviour of the configure flag thus:
>
> --with-libstdcxx-zoneinfo-dir=
> unspecified : Set _GLIBCXX_ZONEINFO_DIR to a default suitable for $host
> yes : Set _GLIBCXX_ZONEINFO_DIR to a default suitable for $host
> no : Do not set _GLIBCXX_ZONEINFO_DIR
>
> What's the use case for "no"? Enforcing a UTC-only tzdb that doesn't even try
> to load the tzdata? If that's desirable, we could #ifdef huge parts of
> src/c++20/tzdb.cc to make the library smaller. That might make sense for a
> toolchain for embedded targets where it's known there's no need for time zone
> conversions.
Actually, I had not explored all those possibilities.
My thinking was that ’no’ is a valid answer and either we need to produce a
configure diagnostic saying that it is not a valid choice - or we should apply
it in some useful way. Silent acceptance but doing something different from
what the user was expecting seems a bad idea.
Your use cases seem quite reasonable - and, yes, I guess that means the code
could be stubbed or given a trivial impl. for that case.
cheers, and season’s greetings,
Iain
>
>
>
> /some/path : set _GLIBCXX_ZONEINFO_DIR = "/some/path"
>
> Signed-off-by: Iain Sandoe <i...@sandoe.co.uk>
>
> libstdc++-v3/ChangeLog:
>
> * acinclude.m4 (GLIBCXX_ZONEINFO_DIR): Revise configure flag
> handling.
> * configure: Regenerate.
> * src/c++20/tzdb.cc: Add a comment that an unset _GLIBCXX_ZONEINFO_DIR
> implies that the configuration specified that no directory should be
> used.
> ---
> libstdc++-v3/acinclude.m4 | 21 ++++++++++++++-------
> libstdc++-v3/configure | 28 +++++++++++++++++++---------
> libstdc++-v3/src/c++20/tzdb.cc | 1 +
> 3 files changed, 34 insertions(+), 16 deletions(-)
>
> diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
> index f73946a4918..3653822aed4 100644
> --- a/libstdc++-v3/acinclude.m4
> +++ b/libstdc++-v3/acinclude.m4
> @@ -5153,18 +5153,25 @@ AC_DEFUN([GLIBCXX_ZONEINFO_DIR], [
> AC_ARG_WITH([libstdcxx-zoneinfo-dir],
> AC_HELP_STRING([--with-libstdcxx-zoneinfo-dir],
> [the directory to search for tzdata files]),
> - [zoneinfo_dir="${withval}"
> - AC_DEFINE(_GLIBCXX_ZONEINFO_DIR, "${withval}",
> - [Define if a non-default location should be used for tzdata files.])
> - ],
> - [
> + [],[with_libstdcxx_zoneinfo_dir=yes])
> +
> + # Pick a default when no specific path is set.
> + if test x${with_libstdcxx_zoneinfo_dir} = xyes; then
> case "$host" in
> # *-*-aix*) zoneinfo_dir="/usr/share/lib/zoneinfo" ;;
> + *-*-darwin2*) zoneinfo_dir="/usr/share/lib/zoneinfo.default" ;;
> *) zoneinfo_dir="/usr/share/zoneinfo" ;;
> esac
> - ])
> -
> + elif test x${with_libstdcxx_zoneinfo_dir} = xno; then
> + zoneinfo_dir=none
> + else
> + zoneinfo_dir=${with_libstdcxx_zoneinfo_dir}
> + fi
> AC_MSG_NOTICE([zoneinfo data directory: ${zoneinfo_dir}])
> + if test x${zoneinfo_dir} != xnone; then
> + AC_DEFINE_UNQUOTED(_GLIBCXX_ZONEINFO_DIR, "${zoneinfo_dir}",
> + [Define if a non-default location should be used for tzdata files.])
> + fi
> ])
>
> # Macros from the top-level gcc directory.
>
> diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
> index 5f5c4199f65..c4311d0902a 100644
> --- a/libstdc++-v3/src/c++20/tzdb.cc
> +++ b/libstdc++-v3/src/c++20/tzdb.cc
> @@ -52,6 +52,7 @@
> # endif
> #endif
>
> +// This is a bit odd; the configure-time setting was 'no zoneinfo directory'
> #ifndef _GLIBCXX_ZONEINFO_DIR
> # define _GLIBCXX_ZONEINFO_DIR "/usr/share/zoneinfo"
> #endif
> --
> 2.37.1 (Apple Git-137.1)
