Re: [PATCH v2 3/3] Fold compat_symbol_unique functionality into compat_symbol

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 19/03/2021 17:07, Florian Weimer via Libc-alpha wrote:
> This eliminates the need for intermediate aliases for defining
> multiple symbol versions, for both compat_symbol and
> versioned_symbol.  Some binutils versions do not suport multiple
> versions per symbol on some targets, so aliases are automatically
> introduced, similar to what compat_symbol_unique did.  To reduce
> symbol table sizes, a configure check is added to avoid these
> aliases if they are not needed.
> 
> The new mechanism works with data symbols as well as function symbols,
> due to the way an assembler-level redirect is used.  It is not
> compatible with weak symbols for old binutils versions, which is why
> the definition of __malloc_initialize_hook had to be changed.  This
> is not a loss of functionality because weak symbols do not matter
> to dynamic linking.
> 
> The placeholder symbol needs repeating in nptl/libpthread-compat.c
> now that compat_symbol is used, but that seems more obvious than
> introducing yet another macro.
> 
> A subtle difference was that compat_symbol_unique made the symbol
> global automatically.  compat_symbol does not do this, so static
> had to be removed from the definition of
> __libpthread_version_placeholder.
> 
> To verify the versioned_symbol functionality, the explicit aliases
> are eliminated from the clock_* function definitions.

LGTM with the common symbol fixes for the malloc hook we discussed
previously.

Reviewed-by: Adhemeval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  config.h.in                   |  4 ++
>  configure                     | 28 +++++++++++++
>  configure.ac                  | 23 +++++++++++
>  include/libc-symbols.h        |  5 ++-
>  include/shlib-compat.h        | 78 ++++++++++++++++-------------------
>  malloc/malloc.c               |  2 +-
>  nptl/libpthread-compat.c      | 16 +++----
>  sysdeps/generic/libc-symver.h | 56 +++++++++++++++++++++++--
>  sysdeps/ia64/libc-symver.h    | 33 +++++++++++++++
>  time/clock_getcpuclockid.c    |  3 +-
>  time/clock_getres.c           |  3 +-
>  time/clock_gettime.c          |  3 +-
>  time/clock_nanosleep.c        |  3 +-
>  time/clock_settime.c          |  3 +-
>  14 files changed, 193 insertions(+), 67 deletions(-)
>  create mode 100644 sysdeps/ia64/libc-symver.h
> 
> diff --git a/config.h.in b/config.h.in
> index f21bf04e47..ca1547ae67 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -190,6 +190,10 @@
>  /* Define if the linker defines __ehdr_start.  */
>  #undef HAVE_EHDR_START
>  
> +/* Define to 1 if the assembler needs intermediate aliases to define
> +   multiple symbol versions for one symbol.  */
> +#define SYMVER_NEEDS_ALIAS 0
> +
>  /*
>  \f */
>  

Ok.

> diff --git a/configure b/configure
> index 37cef37413..bf33439a7f 100755
> --- a/configure
> +++ b/configure
> @@ -6590,6 +6590,34 @@ elif test "$libc_cv_ehdr_start" = broken; then
>  $as_echo "$as_me: WARNING: linker is broken -- you should upgrade" >&2;}
>  fi
>  
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the assembler requires one version per symbol" >&5
> +$as_echo_n "checking whether the assembler requires one version per symbol... " >&6; }
> +if ${libc_cv_symver_needs_alias+:} false; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +    cat > conftest.s <<EOF
> +        .text
> +testfunc:
> +        .globl testfunc
> +        .symver testfunc, testfunc1@VERSION1
> +        .symver testfunc, testfunc1@VERSION2
> +EOF
> +  libc_cv_symver_needs_alias=no
> +  if ${CC-cc} $ASFLAGS -c conftest.s 2>&5; then
> +    libc_cv_symver_needs_alias=no
> +  else
> +    libc_cv_symver_needs_alias=yes
> +  fi
> +  rm conftest.*
> +
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_symver_needs_alias" >&5
> +$as_echo "$libc_cv_symver_needs_alias" >&6; }
> +if test "$libc_cv_symver_needs_alias" = yes; then
> +  $as_echo "#define SYMVER_NEEDS_ALIAS 1" >>confdefs.h
> +
> +fi
> +
>  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_trap with no external dependencies" >&5
>  $as_echo_n "checking for __builtin_trap with no external dependencies... " >&6; }
>  if ${libc_cv_builtin_trap+:} false; then :
> diff --git a/configure.ac b/configure.ac
> index 16b15b6f90..7225f35ea6 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1673,6 +1673,29 @@ elif test "$libc_cv_ehdr_start" = broken; then
>    AC_MSG_WARN([linker is broken -- you should upgrade])
>  fi
>  
> +dnl Starting with binutils 2.35, GAS can attach multiple symbol versions
> +dnl to one symbol (PR 23840).
> +AC_CACHE_CHECK(whether the assembler requires one version per symbol,
> +               libc_cv_symver_needs_alias, [dnl
> +  cat > conftest.s <<EOF
> +        .text
> +testfunc:
> +        .globl testfunc
> +        .symver testfunc, testfunc1@VERSION1
> +        .symver testfunc, testfunc1@VERSION2
> +EOF
> +  libc_cv_symver_needs_alias=no
> +  if ${CC-cc} $ASFLAGS -c conftest.s 2>&AS_MESSAGE_LOG_FD; then
> +    libc_cv_symver_needs_alias=no
> +  else
> +    libc_cv_symver_needs_alias=yes
> +  fi
> +  rm conftest.*
> +])
> +if test "$libc_cv_symver_needs_alias" = yes; then
> +  AC_DEFINE(SYMVER_NEEDS_ALIAS)
> +fi
> +
>  AC_CACHE_CHECK(for __builtin_trap with no external dependencies,
>  	       libc_cv_builtin_trap, [dnl
>  libc_cv_builtin_trap=no
> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> index ce5f75a1a2..546fc26a7b 100644
> --- a/include/libc-symbols.h
> +++ b/include/libc-symbols.h
> @@ -404,12 +404,13 @@ for linking")
>    symbol_version_reference(real, name, version)
>  # define default_symbol_version(real, name, version) \
>       _default_symbol_version(real, name, version)
> +/* See <libc-symver.h>.  */
>  # ifdef __ASSEMBLER__
>  #  define _default_symbol_version(real, name, version) \
> -     .symver real, name##@##@##version
> +  _set_symbol_version (real, name@@version)
>  # else
>  #  define _default_symbol_version(real, name, version) \
> -     __asm__ (".symver " #real "," #name "@@" #version)
> +  _set_symbol_version (real, #name "@@" #version)
>  # endif
>  
>  /* Evalutes to a string literal for VERSION in LIB.  */

Ok.

> diff --git a/include/shlib-compat.h b/include/shlib-compat.h
> index b874e2588f..6429ed2275 100644
> --- a/include/shlib-compat.h
> +++ b/include/shlib-compat.h
> @@ -62,6 +62,16 @@
>     i.e. either GLIBC_2.1 or the "earliest version" specified in
>     shlib-versions if that is newer.  */
>  
> +/* versioned_symbol (LIB, LOCAL, SYMBOL, VERSION) emits a definition
> +   of SYMBOL with a default (@@) VERSION appropriate for LIB.  (The
> +   actually emited symbol version is adjusted according to the

s/emited/emitted

> +   baseline symbol version for LIB.)  The address of the symbol is
> +   taken from LOCAL.  Properties of LOCAL are copied to the exported
> +   symbol.  In particular, LOCAL itself should be global.  It is
> +   unspecified whether SYMBOL@VERSION is associated with LOCAL, or if
> +   an intermediate alias is created.  If LOCAL and SYMBOL are
> +   distinct, and LOCAL is also intended for export, its version should
> +   be specified explicitly with versioned_symbol, too. */
>  # define versioned_symbol(lib, local, symbol, version) \
>    versioned_symbol_1 (lib, local, symbol, version)
>  # define versioned_symbol_1(lib, local, symbol, version) \

Ok.

> @@ -69,44 +79,25 @@
>  # define versioned_symbol_2(local, symbol, name) \
>    default_symbol_version (local, symbol, name)
>  
> +/* compat_symbol is like versioned_symbol, but emits a compatibility
> +   version (with @ instead of @@).  The same issue related to
> +   intermediate aliases applies, so LOCAL should not be listed in the
> +   Versions file, or otherwise it can be exported with an undesired
> +   default symbol version.  */

Ok.

>  # define compat_symbol(lib, local, symbol, version) \
> -  compat_symbol_reference (lib, local, symbol, version)
> -
> -/* This is similar to compat_symbol, but allows versioning the same symbol
> -   to multiple version without having multiple symbol definitions.  For
> -   instance:
> -
> -   #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
> -   compat_symbol_unique (libc, old_foo, GLIBC_2_1_2)
> -   #endif
> -
> -   #if (SHLIB_COMPAT (libpthread, GLIBC_2_2_6, GLIBC_2_3))
> -   compat_symbol_unique (libc, old_foo, GLIBC_2_2_6)
> -   #endif
> -
> -   Internally it creates a unique strong alias to the input symbol and
> -   creates one compat_symbol on the alias.  Using the above example,
> -   it is similar to:
> -
> -   #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
> -   strong_alias (old_foo, old_foo__COUNTER__)
> -   compat_symbol (libc, old_foo__COUNTER__, foo, GLIBC_2_2)
> -   #endif.
> -
> -   With __COUNTER__ being a monotonic number generated by the compiler.  */
> -
> -# define __compat_symbol_unique_concat(x, y) x ## y
> -# define _compat_symbol_unique_concat(x, y) \
> -  __compat_symbol_unique_concat (x, y)
> -# define _compat_symbol_unique_alias(name) \
> -  _compat_symbol_unique_concat (name, __COUNTER__)
> -# define _compat_symbol_unique(lib, orig_name, name, version) \
> -  strong_alias (orig_name, name) \
> -  compat_symbol (lib, name, orig_name, version)
> -# define compat_symbol_unique(lib, name, version) \
> -  _compat_symbol_unique (lib, name, _compat_symbol_unique_alias (name), \
> -                         version)
> -
> +  compat_symbol_1 (lib, local, symbol, version)
> +# define compat_symbol_1(lib, local, symbol, version) \
> +  compat_symbol_2 (local, symbol, VERSION_##lib##_##version)
> +/* See <libc-symver.h>.  */
> +# ifdef __ASSEMBLER__
> +#define compat_symbol_2(local, symbol, name) \
> +  _set_symbol_version (local, symbol@name)
> +# else
> +#  define compat_symbol_2(local, symbol, name) \
> +  compat_symbol_3 (local, symbol, name)
> +#  define compat_symbol_3(local, symbol, name) \
> +  _set_symbol_version (local, #symbol "@" #name)
> +# endif
>  #else
>  
>  /* Not compiling ELF shared libraries at all, so never any old versions.  */
> @@ -118,16 +109,17 @@
>  
>  /* This should not appear outside `#if SHLIB_COMPAT (...)'.  */
>  # define compat_symbol(lib, local, symbol, version) ...
> -# define compat_symbol_unique(lib, name, version) ...
>  
>  #endif
>  

Ok.

>  /* Use compat_symbol_reference for a reference *or* definition of a
> -   specific version of a symbol.  Definitions are primarily used to
> -   ensure tests reference the exact compat symbol required, or define an
> -   interposing symbol of the right version e.g. __malloc_initialize_hook
> -   in mcheck-init.c.  Use compat_symbol to define such a symbol within
> -   the shared libraries that are built for users.  */
> +   specific version of a symbol.  compat_symbol_reference does not
> +   create intermediate aliases.  Definitions are primarily used to
> +   ensure tests reference the exact compat symbol required, or define
> +   an interposing symbol of the right version e.g.,
> +   __malloc_initialize_hook in mcheck-init.c.  Use compat_symbol to
> +   define such a symbol within the shared libraries that are built for
> +   users.  */
>  #define compat_symbol_reference(lib, local, symbol, version) \
>    compat_symbol_reference_1 (lib, local, symbol, version)
>  #define compat_symbol_reference_1(lib, local, symbol, version) \

Ok.

> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 1f4bbd8edf..f23027c13d 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -1991,7 +1991,7 @@ static void *memalign_hook_ini (size_t alignment, size_t sz,
>                                  const void *caller) __THROW;
>  
>  #if HAVE_MALLOC_INIT_HOOK
> -void weak_variable (*__malloc_initialize_hook) (void) = NULL;
> +void (*__malloc_initialize_hook) (void);
>  compat_symbol (libc, __malloc_initialize_hook,
>  	       __malloc_initialize_hook, GLIBC_2_0);
>  #endif

Ok (with the common attribute fix).

> diff --git a/nptl/libpthread-compat.c b/nptl/libpthread-compat.c
> index 820dcd6a8f..da537af76e 100644
> --- a/nptl/libpthread-compat.c
> +++ b/nptl/libpthread-compat.c
> @@ -20,10 +20,10 @@
>  #include <shlib-compat.h>
>  
>  #ifdef SHARED
> -static void
> +void
>  attribute_compat_text_section
>  __attribute_used__
> -__libpthread_version_placeholder (void)
> +__libpthread_version_placeholder_1 (void)
>  {
>  }
>  #endif
> @@ -37,16 +37,16 @@ __libpthread_version_placeholder (void)
>     there are plenty of other symbols which populate those later
>     versions.  */
>  #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
> -compat_symbol_unique (libpthread,
> -		      __libpthread_version_placeholder, GLIBC_2_1_2);
> +compat_symbol (libpthread, __libpthread_version_placeholder_1,
> +	       __libpthread_version_placeholder, GLIBC_2_1_2);
>  #endif
>  
>  #if (SHLIB_COMPAT (libpthread, GLIBC_2_2_3, GLIBC_2_2_4))
> -compat_symbol_unique (libpthread,
> -		      __libpthread_version_placeholder, GLIBC_2_2_3);
> +compat_symbol (libpthread, __libpthread_version_placeholder_1,
> +	       __libpthread_version_placeholder, GLIBC_2_2_3);
>  #endif
>  
>  #if (SHLIB_COMPAT (libpthread, GLIBC_2_2_6, GLIBC_2_3))
> -compat_symbol_unique (libpthread,
> -		      __libpthread_version_placeholder, GLIBC_2_2_6);
> +compat_symbol (libpthread, __libpthread_version_placeholder_1,
> +	       __libpthread_version_placeholder, GLIBC_2_2_6);
>  #endif

Ok.

> diff --git a/sysdeps/generic/libc-symver.h b/sysdeps/generic/libc-symver.h
> index 11c77ae1cd..69d147e2a8 100644
> --- a/sysdeps/generic/libc-symver.h
> +++ b/sysdeps/generic/libc-symver.h
> @@ -22,17 +22,67 @@
>  #ifndef _LIBC_SYMVER_H
>  #define _LIBC_SYMVER_H 1
>  
> +#include <config.h>
> +
>  /* Use symbol_version_reference to specify the version a symbol
>     reference should link to.  Use symbol_version or
>     default_symbol_version for the definition of a versioned symbol.
>     The difference is that the latter is a no-op in non-shared
> -   builds.  */
> +   builds.
> +
> +   _set_symbol_version is similar to symbol_version_reference, except
> +   that this macro expects the name and symbol version as a single
> +   string or token sequence, with an @ or @@ separator.  (A string is
> +   used in C mode and a token sequence in assembler mode.)
> +   _set_symbol_version only be used for definitions because it may
> +   introduce an alias symbol that would not be globally unique for
> +   mere references.  The _set_symbol_version macro is used to define
> +   default_symbol_version and compat_symbol.  */
> +
>  #ifdef __ASSEMBLER__
>  # define symbol_version_reference(real, name, version) \
>       .symver real, name##@##version
> -#else  /* !__ASSEMBLER__ */
> +#else
>  # define symbol_version_reference(real, name, version) \
>    __asm__ (".symver " #real "," #name "@" #version)
> -#endif
> +#endif  /* !__ASSEMBLER__ */
> +
> +#if SYMVER_NEEDS_ALIAS
> +/* If the assembler cannot support multiple versions for the same
> +   symbol, introduce __SInnn_ aliases to which the symbol version is
> +   attached.  */
> +# define __symbol_version_unique_concat(x, y) __SI ## x ## _ ## y
> +# define _symbol_version_unique_concat(x, y) \
> +  __symbol_version_unique_concat (x, y)
> +# define _symbol_version_unique_alias(name) \
> +  _symbol_version_unique_concat (name, __COUNTER__)
> +# ifdef __ASSEMBLER__
> +#  define _set_symbol_version_2(real, alias, name_version) \
> +  .globl alias ASM_LINE_SEP                                \
> +  .equiv alias, real ASM_LINE_SEP                          \
> +  .symver alias, name_version
> +# else
> +#  define _set_symbol_version_2(real, alias, name_version) \
> +  __asm__ (".globl " #alias "\n\t"                         \
> +           ".equiv " #alias ", " #real "\n\t"              \
> +           ".symver " #alias "," name_version)
> +# endif
> +# define _set_symbol_version_1(real, alias, name_version) \
> +  _set_symbol_version_2 (real, alias, name_version)
> +/* REAL must be globally unique, so that the counter also produces
> +   globally unique symbols.  */
> +# define _set_symbol_version(real, name_version)                   \
> +  _set_symbol_version_1 (real, _symbol_version_unique_alias (real), \
> +                               name_version)
> +# else  /* !SYMVER_NEEDS_ALIAS */
> +# ifdef __ASSEMBLER__
> +#  define _set_symbol_version(real, name_version) \
> +  .symver real, name_version
> +# else
> +#  define _set_symbol_version(real, name_version) \
> +  __asm__ (".symver " #real "," name_version)
> +# endif
> +#endif  /* !SYMVER_NEEDS_ALIAS */
> +
>  
>  #endif /* _LIBC_SYMVER_H */

Ok.

> diff --git a/sysdeps/ia64/libc-symver.h b/sysdeps/ia64/libc-symver.h
> new file mode 100644
> index 0000000000..63a3e58dde
> --- /dev/null
> +++ b/sysdeps/ia64/libc-symver.h
> @@ -0,0 +1,33 @@
> +/* Symbol version management.  ia64 version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   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/>.  */
> +
> +#ifndef _LIBC_SYMVER_H
> +
> +#include <sysdeps/generic/libc-symver.h>
> +
> +/* ia64 recognizes loc1 as a register name.  Add the # suffix to all
> +   symbol references.  */
> +#if !defined (__ASSEMBLER__) && SYMVER_NEEDS_ALIAS
> +#undef _set_symbol_version_2
> +# define _set_symbol_version_2(real, alias, name_version) \
> +  __asm__ (".globl " #alias "#\n\t"                         \
> +           ".equiv " #alias ", " #real "#\n\t"              \
> +           ".symver " #alias "#," name_version)
> +#endif
> +
> +#endif /* _LIBC_SYMVER_H */

Ok.

> diff --git a/time/clock_getcpuclockid.c b/time/clock_getcpuclockid.c
> index c148d96c5c..220e2eb016 100644
> --- a/time/clock_getcpuclockid.c
> +++ b/time/clock_getcpuclockid.c
> @@ -42,6 +42,5 @@ versioned_symbol (libc, __clock_getcpuclockid, clock_getcpuclockid, GLIBC_2_17);
>  /* clock_getcpuclockid moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
>  #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
> -strong_alias (__clock_getcpuclockid, __clock_getcpuclockid_2);
> -compat_symbol (libc, __clock_getcpuclockid_2, clock_getcpuclockid, GLIBC_2_2);
> +compat_symbol (libc, __clock_getcpuclockid, clock_getcpuclockid, GLIBC_2_2);
>  #endif

Ok.

> diff --git a/time/clock_getres.c b/time/clock_getres.c
> index 4b31893849..9099b62672 100644
> --- a/time/clock_getres.c
> +++ b/time/clock_getres.c
> @@ -32,8 +32,7 @@ versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
>  /* clock_getres moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
>  #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
> -strong_alias (__clock_getres, __clock_getres_2);
> -compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2);
> +compat_symbol (libc, __clock_getres, clock_getres, GLIBC_2_2);
>  #endif
>  
>  stub_warning (clock_getres)

Ok.

> diff --git a/time/clock_gettime.c b/time/clock_gettime.c
> index fdeaaca3f8..e8e129d201 100644
> --- a/time/clock_gettime.c
> +++ b/time/clock_gettime.c
> @@ -33,8 +33,7 @@ versioned_symbol (libc, __clock_gettime, clock_gettime, GLIBC_2_17);
>  /* clock_gettime moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
>  #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
> -strong_alias (__clock_gettime, __clock_gettime_2);
> -compat_symbol (libc, __clock_gettime_2, clock_gettime, GLIBC_2_2);
> +compat_symbol (libc, __clock_gettime, clock_gettime, GLIBC_2_2);
>  #endif
>  
>  stub_warning (clock_gettime)

Ok.

> diff --git a/time/clock_nanosleep.c b/time/clock_nanosleep.c
> index 7ecb1cfcb8..57b3af2a70 100644
> --- a/time/clock_nanosleep.c
> +++ b/time/clock_nanosleep.c
> @@ -38,8 +38,7 @@ versioned_symbol (libc, __clock_nanosleep, clock_nanosleep, GLIBC_2_17);
>  /* clock_nanosleep moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
>  #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
> -strong_alias (__clock_nanosleep, __clock_nanosleep_2);
> -compat_symbol (libc, __clock_nanosleep_2, clock_nanosleep, GLIBC_2_2);
> +compat_symbol (libc, __clock_nanosleep, clock_nanosleep, GLIBC_2_2);
>  #endif
>  
>  stub_warning (clock_nanosleep)

Ok.

> diff --git a/time/clock_settime.c b/time/clock_settime.c
> index 7676aaeb23..4df4ec56d1 100644
> --- a/time/clock_settime.c
> +++ b/time/clock_settime.c
> @@ -33,8 +33,7 @@ versioned_symbol (libc, __clock_settime, clock_settime, GLIBC_2_17);
>  /* clock_settime moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
>  #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
> -strong_alias (__clock_settime, __clock_settime_2);
> -compat_symbol (libc, __clock_settime_2, clock_settime, GLIBC_2_2);
> +compat_symbol (libc, __clock_settime, clock_settime, GLIBC_2_2);
>  #endif
>  
>  stub_warning (clock_settime)
> 

Ok.