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glibc/sysdeps/mach/hurd/x86_64/dl-tls-initialized.c

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hurd: Only check for TLS initialization inside rtld or in static builds When glibc is built as a shared library, TLS is always initialized by the call of TLS_INIT_TP () macro made inside the dynamic loader, prior to running the main program (see dl-call_tls_init_tp.h). We can take advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate to 0 in all other cases, so let the compiler know that explicitly too. Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same conditions (either !SHARED or inside rtld), to statically assert that this is the case. Other than a microoptimization, this also helps with avoiding awkward sharing of the __libc_tls_initialized variable between ld.so and libc.so that we would have to do otherwise -- we know for sure that no sharing is required, simply because __libc_tls_initialized would always be set to true inside libc.so. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230319151017.531737-25-bugaevc@gmail.com>
2023-03-19 15:10:07 +00:00
/* Determine whether TLS is initialized, for x86_64/Hurd.
Update copyright dates with scripts/update-copyrights
2024-01-01 18:12:26 +00:00
Copyright (C) 1995-2024 Free Software Foundation, Inc.
hurd: Only check for TLS initialization inside rtld or in static builds When glibc is built as a shared library, TLS is always initialized by the call of TLS_INIT_TP () macro made inside the dynamic loader, prior to running the main program (see dl-call_tls_init_tp.h). We can take advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate to 0 in all other cases, so let the compiler know that explicitly too. Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same conditions (either !SHARED or inside rtld), to statically assert that this is the case. Other than a microoptimization, this also helps with avoiding awkward sharing of the __libc_tls_initialized variable between ld.so and libc.so that we would have to do otherwise -- we know for sure that no sharing is required, simply because __libc_tls_initialized would always be set to true inside libc.so. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230319151017.531737-25-bugaevc@gmail.com>
2023-03-19 15:10:07 +00:00
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#if !defined (SHARED) || IS_IN (rtld)
unsigned short __libc_tls_initialized;
#endif
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