pthread_stubs.5 (2010 09)

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pthread_stubs(5) pthread_stubs(5)

NAME

pthread_stubs - list of pthread calls for which the stubs are provided in the C library

DESCRIPTION

The libc shared libraries in libc cumulative patches,

PHCO_22923 (11.00) and PHCO_23772 (11.11)

onwards, contain stubs for the pthread functions in

libpthread and libcma. The stubs allow non-

threaded applications to dynamically load thread-safe libraries successfully, so that the pthread symbols

are resolved. Applications that resolve pthread/cma calls to the stub must be built without

-lpthread

or -lcma on the link line. Stubs provided in

libc do not have any functionality, these are dummy func-

tions returning zero, except the pthread_getspeciﬁc(3T) family of APIs, which have full functionality

implemented in the stubs.

The pthread calls to any of the stub functions below return zero.

pthread_atfork(3T)

pthread_attr_destroy(3T)

pthread_attr_getdetachstate(3T)

pthread_attr_getguardsize(3T)

pthread_attr_getinheritsched(3T)

pthread_attr_getschedparam(3T)

pthread_attr_getschedpolicy(3T)

pthread_attr_getscope(3T)

pthread_attr_getstackaddr(3T)

pthread_attr_getstacksize(3T)

pthread_attr_setdetachstate(3T)

pthread_attr_setguardsize(3T)

pthread_attr_setinheritsched(3T)

pthread_attr_setschedparam(3T)

pthread_attr_setschedpolicy(3T)

pthread_attr_setscope(3T)

pthread_attr_setstackaddr(3T)

pthread_attr_setstacksize(3T)

pthread_cancel(3T)

pthread_cond_broadcast(3T)

pthread_cond_destroy(3T)

pthread_cond_init(3T)

pthread_cond_signal(3T)

pthread_cond_timedwait(3T)

pthread_cond_wait(3T)

pthread_condattr_destroy(3T)

pthread_condattr_getpshared(3T)

pthread_condattr_init(3T)

pthread_condattr_setpshared(3T)

pthread_continue(3T)

pthread_detach(3T)

pthread_getconcurrency(3T)

pthread_getschedparam(3T)

pthread_join (3T)

pthread_kill (3T)

pthread_mutex_destroy(3T)

pthread_mutex_getprioceiling(3T)

pthread_mutex_init(3T)

pthread_mutex_lock(3T)

pthread_mutex_setprioceiling(3T)

pthread_mutex_trylock(3T)

pthread_mutex_unlock(3T)

pthread_mutexattr_destroy(3T)

pthread_mutexattr_getprioceiling(3T)

pthread_mutexattr_getprotocol(3T)

pthread_mutexattr_getpshared(3T)

pthread_mutexattr_gettype(3T)

pthread_mutexattr_init(3T)

pthread_mutexattr_setprioceiling(3T)

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (8 pages)

PAGE 1
pthread_stubs(5) pthread_stubs(5) NAME pthread_stubs - list of pthread calls for which the stubs are provided in the C library DESCRIPTION The libc shared libraries in libc cumulative patches, PHCO_22923 (11.00) and PHCO_23772 (11.11) onwards, contain stubs for the pthread functions in libpthread and libcma. The stubs allow nonthreaded applications to dynamically load thread-safe libraries successfully, so that the pthread symbols are resolved.
PAGE 2
pthread_stubs(5) pthread_stubs(5) pthread_mutexattr_setprotocol(3T) pthread_mutexattr_setpshared(3T) pthread_mutexattr_settype(3T) pthread_once (3T) pthread_rwlock_destroy(3T) pthread_rwlock_init(3T) pthread_rwlock_rdlock(3T) pthread_rwlock_tryrdlock(3T) pthread_rwlock_trywrlock(3T) pthread_rwlock_unlock(3T) pthread_rwlock_wrlock(3T) pthread_rwlockattr_destroy(3T) pthread_rwlockattr_getpshared(3T) pthread_rwlockattr_init (3T) pthread_rwlockattr_setpshared(3T) pthread_self (3T) pthread_setcancelstate(3T) p
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pthread_stubs(5) pthread_stubs(5) Example 1 An application or any library linked, that requires pthread/cma calls to resolve to the pthread stubs in libc must be built without -lpthread or -lcma on the link line. If -lc is specified before -lpthread or -lcma on the link line, pthread/cma calls resolve to pthread stubs in libc. This may lead to problems as given in the examples below: $ cat thread.c #include #include
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pthread_stubs(5) pthread_stubs(5) dynamic /usr/lib/libpthread.1 dynamic /usr/lib/libc.2 shared library binding: deferred global hash table disabled ... Example 2 Specifying -lc before -lpthread in threaded applications can cause run-time problems like the following because the pthread calls get resolved to stubs in libc rather than the functions in pthread library. • Calls to pthread functions fail, due to uninitialized internal structures. • Calls to gethostbyname(3N) fail and return null.
PAGE 5
pthread_stubs(5) pthread_stubs(5) Due to the problems mentioned above, -lc should never be specified in the build command of an executable or shared library. By default, the compiler drivers (cc, aCC, f90) automatically pass -lc to the linker at the end of the link line of the executables. To see if a shared library was built with -lc, look at the shared library list in the chatr output (see chatr (1)), or list the dependent libraries with ldd (see ldd(1)): $ cc +z -c lib1.c $ ld -b -o lib1.sl lib1.
PAGE 6
pthread_stubs(5) pthread_stubs(5) libc.2. The dependency list of the first case is: a.out / \ lib1 lib2 libc | | libc libpthread / Therefore the load graph is constructed as: lib1.sl --> lib2.sl -->libc.2 --> libpthread.1 This is the desired behavior for non-threaded applications, but causes threaded applications (that use either libpthread or libcma) to fail. lib1.sl specifies -lc, lib2.sl specifies -lpthread and no -lpthread on a.out. $ cc -c +z +DA2.0W lib1.c lib2.c lib1.c: lib2.c: $ ld -b -o lib1.
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pthread_stubs(5) pthread_stubs(5) $ cc +DA2.0W thread.c -L. -l1 -l2 $ a.out Error $ ldd a.out lib1.sl => ./lib1.sl lib2.sl => ./lib2.sl libc.2 => /usr/lib/pa20_64/libc.2 libpthread.1 => /lib/pa20_64/libpthread.1 libdl.1 => /usr/lib/pa20_64/libdl.1 $ LD_PRELOAD="/lib/pa20_64/libpthread.1" a.out Success a.out correctly lists -lpthread for a threaded application. $ ld -b -o lib1.sl lib1.o $ ld -b -o lib2.sl -lpthread lib2.o $ cc +DA2.0W thread.c -L. -l1 -l2 -lpthread $ a.out Success $ ldd a.out lib1.sl => .
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(Notes) A (Notes) pA 8 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010