pthread.h: typo in #define pthread_cleanup_push/pthread_cleanup_pop

[Kostik Belousov]

On Tue, Nov 24, 2009 at 05:18:29PM +0200, Mikolaj Golub wrote:
> On Tue, 24 Nov 2009 16:53:35 +0200 Mikolaj Golub wrote:
> 
> > Hi,
> >
> > I have problems with compiling our application under 8.0.
> >
> > It fails due to these definitions in pthread.h that look like a typo or
> > incorrectly applied patch:
> >
> >     170 #define         pthread_cleanup_push(cleanup_routine, cleanup_arg)              \
> >     171                 {                                                               \
> >     172                         struct _pthread_cleanup_info __cleanup_info__;          \
> >     173                         __pthread_cleanup_push_imp(cleanup_routine, cleanup_arg,\
> >     174                                 &__cleanup_info__);                             \
> >     175                         {
> >     176 
> >     177 #define         pthread_cleanup_pop(execute)                                    \
> >     178                         }                                                       \
> >     179                         __pthread_cleanup_pop_imp(execute);                     \
> >     180                 }
> >
> >
> > This patch fixes the problem for me:
> 
> I was hurry when said that the patch fixed the problem. The application
> compiled but later it crashed in pthread_cleanup_pop:
> 
> (gdb) bt
> #0  0xbf4f9ee0 in ?? ()
> #1  0x287d18c9 in __pthread_cleanup_pop_imp () from /lib/libthr.so.3
> #2  0x287d18ed in pthread_cleanup_pop () from /lib/libthr.so.3
> #3  0x287d123c in pthread_exit () from /lib/libthr.so.3
> #4  0x287c7757 in pthread_getprio () from /lib/libthr.so.3
> #5  0x00000000 in ?? ()
> 
> So, I don't know what these macros actually were supposed to be. They were
> introduced in r179662:
> 
> Revision 1.43: download - view: text, markup, annotated - select for diffs
> Mon Jun 9 01:14:10 2008 UTC (17 months, 2 weeks ago) by davidxu
> Branches: MAIN
> Diff to: previous 1.42: preferred, colored
> Changes since revision 1.42: +21 -2 lines
> 
> SVN rev 179662 on 2008-06-09 01:14:10Z by davidxu
> 
> Make pthread_cleanup_push() and pthread_cleanup_pop() as a pair of macros,
> use stack space to keep cleanup information, this eliminates overhead of
> calling malloc() and free() in thread library.
> 
> Discussed on: thread@
> 
> > --- pthread.h.orig    2009-11-24 16:44:13.000000000 +0200
> > +++ pthread.h   2009-11-24 16:44:45.000000000 +0200
> > @@ -172,10 +172,10 @@
> >                         struct _pthread_cleanup_info __cleanup_info__;          \
> >                         __pthread_cleanup_push_imp(cleanup_routine, cleanup_arg,\
> >                                 &__cleanup_info__);                             \
> > -                       {
> > +               }       
> >  
> >  #define                pthread_cleanup_pop(execute)                                    \
> > -                       }                                                       \
> > +               {                                                       \
> >                         __pthread_cleanup_pop_imp(execute);                     \
> >                 }

pthread_cleanup_push/pop are supposed to be used from the common
lexical scope. Citation from SUSv4:

These functions may be implemented as macros. The application shall
ensure that they appear as statements, and in pairs within the same
lexical scope (that is, the pthread_cleanup_push() macro may be
thought to expand to a token list whose first token is '{' with
pthread_cleanup_pop() expanding to a token list whose last token is the
corresponding '}' ).

Your change is wrong.

Basically, the code should do
	pthread_cleanup_push(some_func, arh);
	something ...
	pthread_cleanup_pop(1);
(1 denotes that some_func should be called).
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