Iain reported that he's seeing this on Darwin:
include/bits/chrono_io.h:914: warning: ISO C++ forbids converting a string
constant to 'char*' [-Wwrite-strings]
This is because the BSD definition ot tm::tm_zone is a char* (and has
been since 1987) rather than const char* as in Glibc and POSIX.1-2024.
This uses const_cast<char*> when setting the tm_zone member. This should
be safe because libc doesn't actually write anything to tm_zone, it's
only non-const because the BSD definition predates the addition of the
const keyword to C.
For targets where it's a const char* the cast won't matter because it
will be converted back to const char* on assignment anyway.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__formatter_chrono::_M_c): Use
const_cast when setting tm.tm_zone.
---
Testing x86_64-linux.
libstdc++-v3/include/bits/chrono_io.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h
b/libstdc++-v3/include/bits/chrono_io.h
index 08969166d2f..c55b651d049 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -907,21 +907,22 @@ namespace __format
#ifdef _GLIBCXX_HAVE_STRUCT_TM_TM_ZONE
// POSIX.1-2024 adds tm.tm_zone which will be used for %Z.
+ // BSD has had tm_zone since 1987 but as char* so cast away const.
if constexpr (__is_time_point_v<_Tp>)
{
// One of sys_time, utc_time, or local_time.
if constexpr (!is_same_v<typename _Tp::clock, local_t>)
- __tm.tm_zone = "UTC";
+ __tm.tm_zone = const_cast<char*>("UTC");
}
else if constexpr (__is_specialization_of<_Tp, __local_time_fmt>)
{
// local-time-format-t is used to provide time zone info for
// one of zoned_time, tai_time, gps_time, or local_time.
if (__t._M_abbrev)
- __tm.tm_zone = __t._M_abbrev->c_str();
+ __tm.tm_zone = const_cast<char*>(__t._M_abbrev->c_str());
}
else
- __tm.tm_zone = "UTC";
+ __tm.tm_zone = const_cast<char*>("UTC");
#endif
auto __d = _S_days(__t); // Either sys_days or local_days.
--
2.49.0
