Tested x86_64-linux. Pushed to trunk.
-- >8 --
chrono::tzdb::current_zone uses filesystem::read_symlink, which creates
a dependency on the fs_ops.o object in libstdc++.a, which then creates
dependencies on several OS functions if --gc-sections isn't used. For
more details see PR libstdc++/104167 comment 8 and comment 11.
In the cases where that causes linker failures, we probably don't have
readlink anyway, so the filesystem::read_symlink call will always fail.
Repeat the preprocessor conditions for filesystem::read_symlink in the
body of chrono::tzdb::current_zone so that we don't create a
dependency on fs_ops.o for a function that will always fail.
libstdc++-v3/ChangeLog:
* src/c++20/tzdb.cc (tzdb::current_zone): Check configure macros
for POSIX readlink before using filesystem::read_symlink.
---
libstdc++-v3/src/c++20/tzdb.cc | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 0fcbf6a4824..d22cea7e070 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -1635,6 +1635,9 @@ namespace std::chrono
// TODO cache this function's result?
#ifndef _AIX
+ // Repeat the preprocessor condition used by filesystem::read_symlink,
+ // to avoid a dependency on src/c++17/fs_ops.o if it won't work anyway.
+#if defined(_GLIBCXX_HAVE_READLINK) && defined(_GLIBCXX_HAVE_SYS_STAT_H)
error_code ec;
// This should be a symlink to e.g. /usr/share/zoneinfo/Europe/London
auto path = filesystem::read_symlink("/etc/localtime", ec);
@@ -1653,6 +1656,7 @@ namespace std::chrono
return tz;
}
}
+#endif
// Otherwise, look for a file naming the time zone.
string_view files[] {
"/etc/timezone", // Debian derivates
--
2.41.0
