https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99832
John David Anglin <danglin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |danglin at gcc dot gnu.org
--- Comment #5 from John David Anglin <danglin at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #1)
> Maybe something like this:
>
> diff --git a/libstdc++-v3/config/os/gnu-linux/os_defines.h
> b/libstdc++-v3/config/os/gnu-linux/os_defines.h
> index 0af29325388..f7c73560831 100644
> --- a/libstdc++-v3/config/os/gnu-linux/os_defines.h
> +++ b/libstdc++-v3/config/os/gnu-linux/os_defines.h
> @@ -84,7 +84,13 @@
> // Since glibc 2.34 all pthreads functions are usable without linking to
> // libpthread.
> # define _GLIBCXX_GTHREAD_USE_WEAK 0
> -# endif
> +// Since glibc 2.34 using -D_TIME_BITS=64 will enable 64-bit time_t
> +// for "legacy ABIs", i.e. ones that historically used 32-bit time_t.
> +// This internal glibc macro will be defined iff new 64-bit time_t is in
> use.
> +# ifdef __USE_TIME_BITS64
> +# define _GLIBCXX_TIME_BITS64 1
> +# endif
> +# endif // glibc 2.34
> #endif // __linux__
>
> #endif
> diff --git a/libstdc++-v3/include/bits/chrono.h
> b/libstdc++-v3/include/bits/chrono.h
> index 579c5a266be..a63782b92ff 100644
> --- a/libstdc++-v3/include/bits/chrono.h
> +++ b/libstdc++-v3/include/bits/chrono.h
> @@ -1242,6 +1242,9 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
> now() noexcept;
>
> // Map to C API
> +#ifdef _GLIBCXX_TIME_BITS64
> + [[__gnu__::__abi_tag__("__time64")]]
> +#endif
> static std::time_t
> to_time_t(const time_point& __t) noexcept
> {
> @@ -1249,6 +1252,9 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
> (__t.time_since_epoch()).count());
> }
>
> +#ifdef _GLIBCXX_TIME_BITS64
> + [[__gnu__::__abi_tag__("__time64")]]
> +#endif
> static time_point
> from_time_t(std::time_t __t) noexcept
> {
>
> Alternatively, in <bits/c++config.h> do:
>
> #define _GLIBCXX_TIME_BITS64_ABI_TAG
>
> and then in config/os/gnu-linux/os_defines.h:
>
>
> # ifdef __USE_TIME_BITS64
> # undef _GLIBCXX_TIME_BITS64_ABI_TAG
> # define _GLIBCXX_TIME_BITS64_ABI_TAG [[__gnu__::__abi_tag__("__time64")]]
> # endif
>
> Then the chrono code can just use that unconditionally instead of using
> #ifdef
>
> I think for musl, newer versions use 64-bit time_t unconditionally. I'm not
> sure if we can (or need to) use the abi_tag there.
The latter causes the following warning on hppa-linux:
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/./prev-gcc/xg++
-B/home/dave/debian
/gcc-15/gcc-15-15.1.0/build/./prev-gcc/ -B/usr/hppa-linux-gnu/bin/ -nostdinc++
-
B/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/s
rc/.libs
-B/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libs
tdc++-v3/libsupc++/.libs
-I/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hp
pa-linux-gnu/libstdc++-v3/include/hppa-linux-gnu
-I/home/dave/debian/gcc-15/gcc
-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include
-I/home/dave/debian/g
cc-15/gcc-15-15.1.0/src/libstdc++-v3/libsupc++
-L/home/dave/debian/gcc-15/gcc-15
-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/src/.libs
-L/home/dave/debian/gcc
-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/libsupc++/.libs
-fno-P
IE -c -g -O2 -fno-checking -DIN_GCC -fno-exceptions -fno-rtti
-fasynchronou
s-unwind-tables -W -Wall -Wno-error=narrowing -Wwrite-strings -Wcast-qual
-Wmiss
ing-format-attribute -Wconditionally-supported -Woverloaded-virtual -pedantic
-W
no-long-long -Wno-variadic-macros -Wno-overlength-strings -DHAVE_CONFIG_H
-fno-
PIE -I. -I. -I../../src/gcc -I../../src/gcc/. -I../../src/gcc/../include
-I../.
./src/gcc/../libcpp/include -I../../src/gcc/../libcody
-I../../src/gcc/../libdecnumber -I../../src/gcc/../libdecnumber/dpd
-I../libdecnumber -I../../src/gcc/../libbacktrace -o ipa-profile.o -MT
ipa-profile.o -MMD -MP -MF ./.deps/ipa-profile.TPo ../../src/gcc/ipa-profile.cc
In file included from
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include/bits/memoryfwd.h:50,
from
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include/memory:65,
from ../../src/gcc/system.h:228,
from ../../src/gcc/ipa-profile.cc:41:
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include/hppa-linux-gnu/bits/c++config.h:955:9:
warning: '_GLIBCXX_TIME_BITS64_ABI_TAG' redefined
955 | #define _GLIBCXX_TIME_BITS64_ABI_TAG
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include/hppa-linux-gnu/bits/c++config.h:727:
/home/dave/debian/gcc-15/gcc-15-15.1.0/build/prev-hppa-linux-gnu/libstdc++-v3/include/hppa-linux-gnu/bits/os_defines.h:92:12:
note: this is the location of the previous definition
92 | # define _GLIBCXX_TIME_BITS64_ABI_TAG
[[__gnu__::__abi_tag__("__time64")]]
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Should the define in c++config.h overrride the define in os_defines.h or
defer to it?
