Bug 3738

Summary: pthread lib not compatible
Product: [Retired] Red Hat Linux Reporter: brownb
Component: glibcAssignee: Cristian Gafton <gafton>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: 6.0   
Target Milestone: ---   
Target Release: ---   
Hardware: i386   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 1999-07-09 21:33:46 UTC Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description brownb 1999-06-25 23:17:49 UTC
The pthread library has changed the size of some data
structures, such as sem_t, but the major version number on
the shared library was not incremented.  Hence, old RH 5.1
binaries that use semaphores segfault on RH 6.0.  Lack of
backward compatibility is a disaster, since it makes
upgrading machines much harder.

Comment 1 Cristian Gafton 1999-07-02 21:19:59 UTC
Do you have example code that breaks between glibc 2.0 and glibc 2.1?

Comment 2 Cristian Gafton 1999-07-09 02:37:59 UTC
Reply from the e-mail message:

Here is the sem_t structure definition from the include files of Red
Hat 5.1.
It's defined in /usr/include/semaphorebits.h.

        typedef struct {
          long int sem_status;
          int sem_spinlock;
        } sem_t;

Here is the Red Hat 6.0 version, from file /usr/include/semaphore.h.

        typedef struct
        {
          struct
          {
            long int status;
            int spinlock;
          } __sem_lock;
          int __sem_value;
          _pthread_descr __sem_waiting;
        } sem_t;

You'll notice that the second structure is larger than the first.
When a Red
Hat 5.1 program runs on Red Hat 6.0 and calls sem_init, the function
modifies
memory off the end of the space the program allocated for the sem_t
object.

Since the size of the data structure changed, the shared object should
have
been versioned, so that old programs got the older version of
sem_init.

Is this enough explanation?  All of the real applications that break
in my
environment are GUI tools.  If needed I could write a test program
demonstrating the problem.

                                bob

Comment 3 Cristian Gafton 1999-07-09 21:33:59 UTC
Fixed in glibc-2.1.2-1