Force building with -fno-common

  As a result, is not necessary to specify __attribute__ ((nocommon))
on individual definitions.

GCC 10 defaults to -fno-common on all architectures except ARC,
but this change is compatible with older GCC versions and ARC, too.

Not sure if this is still appropriate at this time for glibc 2.34, but
this commit simplifies compatibility symbol work, by reducing GCC
version and architecture divergence.

Tested on i686-linux-gnu and x86_64-linux.  Tested with a full bootstrap
cycle with build-many-glibc.py using the combinations GCC 8/binutils 2.32
and GCC 7/binutils 2.33.  There are some build failures, but they appear
to be unrelated to this change.

---
 Makeconfig                               |  6 +++++-
 csu/libc-start.c                         |  3 +--
 elf/dl-support.c                         |  6 +++---
 elf/rtld.c                               |  3 +--
 include/shlib-compat.h                   |  6 +-----
 malloc/malloc.c                          |  2 +-
 malloc/mtrace.c                          |  2 +-
 misc/regexp.c                            |  9 ++++-----
 nptl/libc_multiple_threads.c             |  2 +-
 nptl/lowlevellock.c                      |  2 +-
 nptl/pthread_create.c                    |  4 ++--
 nptl/pthread_keys.c                      |  3 +--
 nptl/vars.c                              |  6 ++----
 resolv/res_libc.c                        |  2 +-
 stdlib/abort.c                           |  2 +-
 sunrpc/key_call.c                        |  8 +++-----
 sunrpc/rpc_common.c                      | 12 +++++-------
 sunrpc/svcauth_des.c                     |  2 +-
 sysdeps/nptl/dl-tls_init_tp.c            |  4 ++--
 sysdeps/powerpc/nofpu/sim-full.c         |  8 ++++----
 sysdeps/unix/sysv/linux/timer_routines.c |  5 ++---
 21 files changed, 43 insertions(+), 54 deletions(-)
  

On 7/8/21 3:57 PM, Florian Weimer via Libc-alpha wrote:
> As a result, is not necessary to specify __attribute__ ((nocommon))
> on individual definitions.
> 
> GCC 10 defaults to -fno-common on all architectures except ARC,
> but this change is compatible with older GCC versions and ARC, too.
> 
> Not sure if this is still appropriate at this time for glibc 2.34, but
> this commit simplifies compatibility symbol work, by reducing GCC
> version and architecture divergence.
> 
> Tested on i686-linux-gnu and x86_64-linux.  Tested with a full bootstrap
> cycle with build-many-glibc.py using the combinations GCC 8/binutils 2.32
> and GCC 7/binutils 2.33.  There are some build failures, but they appear
> to be unrelated to this change.

Carlos clarified that non-ABI changes are OK during the slushy freeze, 
but you could wait on him for additional approval.

I did a build on x86_64 to verify that the resulting binaries are 
identical (since -fno-common should be nop for gcc11) but turns out 
they're not.  I haven't yet looked at the nature of the change since 
they could be benign but it still was surprising.

Siddhesh
  

* Siddhesh Poyarekar:

> Carlos clarified that non-ABI changes are OK during the slushy freeze,
> but you could wait on him for additional approval.
>
> I did a build on x86_64 to verify that the resulting binaries are
> identical (since -fno-common should be nop for gcc11) but turns out 
> they're not.  I haven't yet looked at the nature of the change since
> they could be benign but it still was surprising.

Line numbering changes in a few places, and that affects asserts.

Thanks,
Florian
  

On 7/9/21 1:35 PM, Florian Weimer wrote:
> * Siddhesh Poyarekar:
> 
>> Carlos clarified that non-ABI changes are OK during the slushy freeze,
>> but you could wait on him for additional approval.
>>
>> I did a build on x86_64 to verify that the resulting binaries are
>> identical (since -fno-common should be nop for gcc11) but turns out
>> they're not.  I haven't yet looked at the nature of the change since
>> they could be benign but it still was surprising.
> 
> Line numbering changes in a few places, and that affects asserts.

Great, in that case, LGTM.  +Carlos for RM approval since the code is 
identical with newer gcc.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
  

On 7/8/21 6:27 AM, Florian Weimer via Libc-alpha wrote:
> As a result, is not necessary to specify __attribute__ ((nocommon))
> on individual definitions.
> 
> GCC 10 defaults to -fno-common on all architectures except ARC,
> but this change is compatible with older GCC versions and ARC, too.
> 
> Not sure if this is still appropriate at this time for glibc 2.34, but
> this commit simplifies compatibility symbol work, by reducing GCC
> version and architecture divergence.
> 
> Tested on i686-linux-gnu and x86_64-linux.  Tested with a full bootstrap
> cycle with build-many-glibc.py using the combinations GCC 8/binutils 2.32
> and GCC 7/binutils 2.33.  There are some build failures, but they appear
> to be unrelated to this change.

LGTM. Anything we can do to reduce version/arch divergence is a win.
This is not an ABI change so I think this could have gone in without
my review, but I'm happy to look it over as RM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
> ---
>  Makeconfig                               |  6 +++++-
>  csu/libc-start.c                         |  3 +--
>  elf/dl-support.c                         |  6 +++---
>  elf/rtld.c                               |  3 +--
>  include/shlib-compat.h                   |  6 +-----
>  malloc/malloc.c                          |  2 +-
>  malloc/mtrace.c                          |  2 +-
>  misc/regexp.c                            |  9 ++++-----
>  nptl/libc_multiple_threads.c             |  2 +-
>  nptl/lowlevellock.c                      |  2 +-
>  nptl/pthread_create.c                    |  4 ++--
>  nptl/pthread_keys.c                      |  3 +--
>  nptl/vars.c                              |  6 ++----
>  resolv/res_libc.c                        |  2 +-
>  stdlib/abort.c                           |  2 +-
>  sunrpc/key_call.c                        |  8 +++-----
>  sunrpc/rpc_common.c                      | 12 +++++-------
>  sunrpc/svcauth_des.c                     |  2 +-
>  sysdeps/nptl/dl-tls_init_tp.c            |  4 ++--
>  sysdeps/powerpc/nofpu/sim-full.c         |  8 ++++----
>  sysdeps/unix/sysv/linux/timer_routines.c |  5 ++---
>  21 files changed, 43 insertions(+), 54 deletions(-)
> 
> diff --git a/Makeconfig b/Makeconfig
> index efc7351d71..68663d984e 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -923,8 +923,12 @@ ifeq	"$(strip $(+cflags))" ""
>  +cflags	:= $(default_cflags)
>  endif	# $(+cflags) == ""
>  
> +# Force building with -fno-common because hidden_def, compat_symbol
> +# and other constructs do not work for common symbols (and would
> +# otherwise require specifying __attribute__ ((nocommon)) on a
> +# case-by-case basis).
>  +cflags += $(cflags-cpu) $(+gccwarn) $(+merge-constants) $(+math-flags) \
> -	   $(+stack-protector)
> +	   $(+stack-protector) -fno-common
>  +gcc-nowarn := -w
>  
>  # Each sysdeps directory can contain header files that both will be
> diff --git a/csu/libc-start.c b/csu/libc-start.c
> index 5b5913e7bf..0350b006fd 100644
> --- a/csu/libc-start.c
> +++ b/csu/libc-start.c
> @@ -52,8 +52,7 @@ uintptr_t __stack_chk_guard attribute_relro;
>  # ifndef  THREAD_SET_POINTER_GUARD
>  /* Only exported for architectures that don't store the pointer guard
>     value in thread local area.  */
> -uintptr_t __pointer_chk_guard_local
> -	attribute_relro attribute_hidden __attribute__ ((nocommon));
> +uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
>  # endif
>  #endif
>  
> diff --git a/elf/dl-support.c b/elf/dl-support.c
> index dfc9ab760e..0155718175 100644
> --- a/elf/dl-support.c
> +++ b/elf/dl-support.c
> @@ -163,8 +163,8 @@ int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
>  ElfW(auxv_t) *_dl_auxv;
>  const ElfW(Phdr) *_dl_phdr;
>  size_t _dl_phnum;
> -uint64_t _dl_hwcap __attribute__ ((nocommon));
> -uint64_t _dl_hwcap2 __attribute__ ((nocommon));
> +uint64_t _dl_hwcap;
> +uint64_t _dl_hwcap2;
>  
>  /* The value of the FPU control word the kernel will preset in hardware.  */
>  fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
> @@ -176,7 +176,7 @@ fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
>     file.  Since there is no way to set this nonzero (we don't grok the
>     LD_HWCAP_MASK environment variable here), there is no real point in
>     setting _dl_hwcap nonzero below, but we do anyway.  */
> -uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
> +uint64_t _dl_hwcap_mask;
>  #endif
>  
>  /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
> diff --git a/elf/rtld.c b/elf/rtld.c
> index fbbd60b446..e3fb2a5b2a 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -163,8 +163,7 @@ uintptr_t __stack_chk_guard attribute_relro;
>  
>  /* Only exported for architectures that don't store the pointer guard
>     value in thread local area.  */
> -uintptr_t __pointer_chk_guard_local
> -     attribute_relro attribute_hidden __attribute__ ((nocommon));
> +uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
>  #ifndef THREAD_SET_POINTER_GUARD
>  strong_alias (__pointer_chk_guard_local, __pointer_chk_guard)
>  #endif
> diff --git a/include/shlib-compat.h b/include/shlib-compat.h
> index 6c423c8cb0..c29a0e081f 100644
> --- a/include/shlib-compat.h
> +++ b/include/shlib-compat.h
> @@ -79,11 +79,7 @@
>     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.
> -
> -   If LOCAL is a data symbol and does not have a non-zero initializer,
> -   it should be defined with __attribute__ ((nocommon)) for
> -   compatibility with GCC versions that default to -fcommon.  */
> +   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) \
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index a3525f71da..ca0f736ac3 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -2026,7 +2026,7 @@ static void *memalign_hook_ini (size_t alignment, size_t sz,
>                                  const void *caller) __THROW;
>  
>  #if HAVE_MALLOC_INIT_HOOK
> -void (*__malloc_initialize_hook) (void) __attribute__ ((nocommon));
> +void (*__malloc_initialize_hook) (void);
>  compat_symbol (libc, __malloc_initialize_hook,
>  	       __malloc_initialize_hook, GLIBC_2_0);
>  #endif
> diff --git a/malloc/mtrace.c b/malloc/mtrace.c
> index f5b8321c6b..6c2c58b706 100644
> --- a/malloc/mtrace.c
> +++ b/malloc/mtrace.c
> @@ -59,7 +59,7 @@ __libc_lock_define_initialized (static, lock);
>     case some applications ended up linking against them but they don't actually
>     do anything anymore; not that they did much before anyway.  */
>  
> -void *mallwatch __attribute__ ((nocommon));
> +void *mallwatch;
>  compat_symbol (libc, mallwatch, mallwatch, GLIBC_2_0);
>  
>  void
> diff --git a/misc/regexp.c b/misc/regexp.c
> index d101afd7a1..ba748756bf 100644
> --- a/misc/regexp.c
> +++ b/misc/regexp.c
> @@ -29,15 +29,14 @@
>  
>  #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_23)
>  
> -/* Define the variables used for the interface.  Avoid .symver on common
> -   symbol, which just creates a new common symbol, not an alias.  */
> -char *loc1 __attribute__ ((nocommon));
> -char *loc2 __attribute__ ((nocommon));
> +/* Define the variables used for the interface.  */
> +char *loc1;
> +char *loc2;
>  compat_symbol (libc, loc1, loc1, GLIBC_2_0);
>  compat_symbol (libc, loc2, loc2, GLIBC_2_0);
>  
>  /* Although we do not support the use we define this variable as well.  */
> -char *locs __attribute__ ((nocommon));
> +char *locs;
>  compat_symbol (libc, locs, locs, GLIBC_2_0);
>  
>  
> diff --git a/nptl/libc_multiple_threads.c b/nptl/libc_multiple_threads.c
> index a0e7932c26..4eeec856ad 100644
> --- a/nptl/libc_multiple_threads.c
> +++ b/nptl/libc_multiple_threads.c
> @@ -23,7 +23,7 @@
>  /* Variable set to a nonzero value either if more than one thread runs or ran,
>     or if a single-threaded process is trying to cancel itself.  See
>     nptl/descr.h for more context on the single-threaded process case.  */
> -int __libc_multiple_threads __attribute__ ((nocommon));
> +int __libc_multiple_threads;
>  libc_hidden_data_def (__libc_multiple_threads)
>  # endif
>  #endif
> diff --git a/nptl/lowlevellock.c b/nptl/lowlevellock.c
> index 2d077d8694..31f11abcda 100644
> --- a/nptl/lowlevellock.c
> +++ b/nptl/lowlevellock.c
> @@ -53,6 +53,6 @@ __lll_lock_wait (int *futex, int private)
>  libc_hidden_def (__lll_lock_wait)
>  
>  #if ENABLE_ELISION_SUPPORT
> -int __pthread_force_elision __attribute__ ((nocommon));
> +int __pthread_force_elision;
>  libc_hidden_data_def (__pthread_force_elision)
>  #endif
> diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
> index d1b6817a81..440adc2a6f 100644
> --- a/nptl/pthread_create.c
> +++ b/nptl/pthread_create.c
> @@ -43,12 +43,12 @@
>  
>  
>  /* Globally enabled events.  */
> -td_thr_events_t __nptl_threads_events __attribute__ ((nocommon));
> +td_thr_events_t __nptl_threads_events;
>  libc_hidden_proto (__nptl_threads_events)
>  libc_hidden_data_def (__nptl_threads_events)
>  
>  /* Pointer to descriptor with the last event.  */
> -struct pthread *__nptl_last_event __attribute__ ((nocommon));
> +struct pthread *__nptl_last_event;
>  libc_hidden_proto (__nptl_last_event)
>  libc_hidden_data_def (__nptl_last_event)
>  
> diff --git a/nptl/pthread_keys.c b/nptl/pthread_keys.c
> index 76e4cfad34..d7bbdd9af7 100644
> --- a/nptl/pthread_keys.c
> +++ b/nptl/pthread_keys.c
> @@ -19,6 +19,5 @@
>  #include <pthreadP.h>
>  
>  /* Table of the key information.  */
> -struct pthread_key_struct __pthread_keys[PTHREAD_KEYS_MAX]
> -  __attribute__ ((nocommon));
> +struct pthread_key_struct __pthread_keys[PTHREAD_KEYS_MAX];
>  libc_hidden_data_def (__pthread_keys)
> diff --git a/nptl/vars.c b/nptl/vars.c
> index 989d7930e0..c3ec368b1b 100644
> --- a/nptl/vars.c
> +++ b/nptl/vars.c
> @@ -22,11 +22,9 @@
>  
>  /* Default thread attributes for the case when the user does not
>     provide any.  */
> -union pthread_attr_transparent __default_pthread_attr
> -  __attribute__ ((nocommon));
> +union pthread_attr_transparent __default_pthread_attr;
>  libc_hidden_data_def (__default_pthread_attr)
>  
>  /* Mutex protecting __default_pthread_attr.  */
> -int __default_pthread_attr_lock __attribute__ ((nocommon))
> -  = LLL_LOCK_INITIALIZER;
> +int __default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
>  libc_hidden_data_def (__default_pthread_attr_lock)
> diff --git a/resolv/res_libc.c b/resolv/res_libc.c
> index 636d238592..41d44caa57 100644
> --- a/resolv/res_libc.c
> +++ b/resolv/res_libc.c
> @@ -88,7 +88,7 @@ res_init (void)
>     This differs from plain `struct __res_state _res;' in that it doesn't
>     create a common definition, but a plain symbol that resides in .bss,
>     which can have an alias.  */
> -struct __res_state _res __attribute__ ((nocommon));
> +struct __res_state _res;
>  
>  #undef __resp
>  __thread struct __res_state *__resp = &_res;
> diff --git a/stdlib/abort.c b/stdlib/abort.c
> index 8f5f4fe6b8..018f735fbf 100644
> --- a/stdlib/abort.c
> +++ b/stdlib/abort.c
> @@ -32,7 +32,7 @@
>  #endif
>  
>  /* Exported variable to locate abort message in core files etc.  */
> -struct abort_msg_s *__abort_msg __attribute__ ((nocommon));
> +struct abort_msg_s *__abort_msg;
>  libc_hidden_def (__abort_msg)
>  
>  /* We must avoid to run in circles.  Therefore we remember how far we
> diff --git a/sunrpc/key_call.c b/sunrpc/key_call.c
> index f13b0a7e4c..8ea4303d7d 100644
> --- a/sunrpc/key_call.c
> +++ b/sunrpc/key_call.c
> @@ -290,11 +290,9 @@ libc_hidden_nolink_sunrpc (key_get_conv, GLIBC_2_1)
>   * implementations of these functions, and to call those in key_call().
>   */
>  
> -cryptkeyres *(*__key_encryptsession_pk_LOCAL) (uid_t, char *)
> -  __attribute__ ((nocommon));
> -cryptkeyres *(*__key_decryptsession_pk_LOCAL) (uid_t, char *)
> -  __attribute__ ((nocommon));
> -des_block *(*__key_gendes_LOCAL) (uid_t, char *) __attribute__ ((nocommon));
> +cryptkeyres *(*__key_encryptsession_pk_LOCAL) (uid_t, char *);
> +cryptkeyres *(*__key_decryptsession_pk_LOCAL) (uid_t, char *);
> +des_block *(*__key_gendes_LOCAL) (uid_t, char *);
>  #ifdef SHARED
>  # ifndef EXPORT_RPC_SYMBOLS
>  compat_symbol (libc, __key_encryptsession_pk_LOCAL,
> diff --git a/sunrpc/rpc_common.c b/sunrpc/rpc_common.c
> index 05abab2a1d..97e90be89c 100644
> --- a/sunrpc/rpc_common.c
> +++ b/sunrpc/rpc_common.c
> @@ -42,15 +42,13 @@
>  /* We are very tricky here.  We want to have _null_auth in a read-only
>     section but we cannot add const to the type because this isn't how
>     the variable is declared.  So we use the section attribute.  */
> -struct opaque_auth _null_auth __attribute__ ((nocommon));
> +struct opaque_auth _null_auth;
>  libc_hidden_nolink_sunrpc (_null_auth, GLIBC_2_0)
>  
> -/* The variables need the nocommon attribute, so that it is possible
> -   to create aliases and specify symbol versions.  */
> -fd_set svc_fdset  __attribute__ ((nocommon));
> -struct rpc_createerr rpc_createerr  __attribute__ ((nocommon));
> -struct pollfd *svc_pollfd  __attribute__ ((nocommon));
> -int svc_max_pollfd  __attribute__ ((nocommon));
> +fd_set svc_fdset;
> +struct rpc_createerr rpc_createerr;
> +struct pollfd *svc_pollfd;
> +int svc_max_pollfd;
>  #ifdef SHARED
>  # ifndef EXPORT_RPC_SYMBOLS
>  compat_symbol (libc, svc_fdset, svc_fdset, GLIBC_2_0);
> diff --git a/sunrpc/svcauth_des.c b/sunrpc/svcauth_des.c
> index 25a85c9097..dba66a0d77 100644
> --- a/sunrpc/svcauth_des.c
> +++ b/sunrpc/svcauth_des.c
> @@ -93,7 +93,7 @@ struct
>      u_long ncachereplays;	/* times cache hit, and is replay */
>      u_long ncachemisses;	/* times cache missed */
>    }
> -svcauthdes_stats __attribute__ ((nocommon));
> +svcauthdes_stats;
>  #ifdef SHARED
>  compat_symbol (libc, svcauthdes_stats, svcauthdes_stats, GLIBC_2_0);
>  #endif
> diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
> index c3349dd14c..ca494dd3a5 100644
> --- a/sysdeps/nptl/dl-tls_init_tp.c
> +++ b/sysdeps/nptl/dl-tls_init_tp.c
> @@ -23,11 +23,11 @@
>  #include <tls.h>
>  
>  #ifndef __ASSUME_SET_ROBUST_LIST
> -bool __nptl_set_robust_list_avail __attribute__ ((nocommon));
> +bool __nptl_set_robust_list_avail;
>  rtld_hidden_data_def (__nptl_set_robust_list_avail)
>  #endif
>  
> -bool __nptl_initial_report_events __attribute__ ((nocommon));
> +bool __nptl_initial_report_events;
>  rtld_hidden_def (__nptl_initial_report_events)
>  
>  #ifdef SHARED
> diff --git a/sysdeps/powerpc/nofpu/sim-full.c b/sysdeps/powerpc/nofpu/sim-full.c
> index 1867e8d305..ab1e97d9ed 100644
> --- a/sysdeps/powerpc/nofpu/sim-full.c
> +++ b/sysdeps/powerpc/nofpu/sim-full.c
> @@ -22,18 +22,18 @@
>  #include "soft-supp.h"
>  
>  /* Thread-local to store sticky exceptions.  */
> -__thread int __sim_exceptions_thread __attribute__ ((nocommon));
> +__thread int __sim_exceptions_thread;
>  libc_hidden_tls_def (__sim_exceptions_thread);
>  
>  /* By default, no exceptions should trap.  */
>  __thread int __sim_disabled_exceptions_thread = 0xffffffff;
>  libc_hidden_tls_def (__sim_disabled_exceptions_thread);
>  
> -__thread int __sim_round_mode_thread __attribute__ ((nocommon));
> +__thread int __sim_round_mode_thread;
>  libc_hidden_tls_def (__sim_round_mode_thread);
>  
>  #if SIM_GLOBAL_COMPAT
> -int __sim_exceptions_global __attribute__ ((nocommon));
> +int __sim_exceptions_global;
>  libc_hidden_data_def (__sim_exceptions_global);
>  SIM_COMPAT_SYMBOL (__sim_exceptions_global, __sim_exceptions);
>  
> @@ -42,7 +42,7 @@ libc_hidden_data_def (__sim_disabled_exceptions_global);
>  SIM_COMPAT_SYMBOL (__sim_disabled_exceptions_global,
>  		   __sim_disabled_exceptions);
>  
> -int __sim_round_mode_global __attribute__ ((nocommon));
> +int __sim_round_mode_global;
>  libc_hidden_data_def (__sim_round_mode_global);
>  SIM_COMPAT_SYMBOL (__sim_round_mode_global, __sim_round_mode);
>  #endif
> diff --git a/sysdeps/unix/sysv/linux/timer_routines.c b/sysdeps/unix/sysv/linux/timer_routines.c
> index 30ad32b4fc..02bad0384e 100644
> --- a/sysdeps/unix/sysv/linux/timer_routines.c
> +++ b/sysdeps/unix/sysv/linux/timer_routines.c
> @@ -107,12 +107,11 @@ timer_helper_thread (void *arg)
>  
>  
>  /* Control variable for helper thread creation.  */
> -pthread_once_t __timer_helper_once __attribute__ ((nocommon))
> -  = PTHREAD_ONCE_INIT;
> +pthread_once_t __timer_helper_once = PTHREAD_ONCE_INIT;
>  
>  
>  /* TID of the helper thread.  */
> -pid_t __timer_helper_tid __attribute__ ((nocommon));
> +pid_t __timer_helper_tid;
>  
>  
>  /* Reset variables so that after a fork a new helper thread gets started.  */
>