RedHat 9, GNAT 3.15p, and Pentium 4 tasking failure/work-around

RedHat 9, GNAT 3.15p, and Pentium 4 tasking failure/work-around

[Marc A. Criley]

On my new system that has the mentioned configuration, programs
compiled with GNAT 3.15p that have tasking hang.

The reason appears to be some sort of incompatibility between GNAT
3.15p tasking and the "Native POSIX Threads Library" (NPTL)
implementation of libpthread.so distributed with RH 9. This
problematic version of libpthread.so resides in
/lib/tls/libpthread.so, while the alternate LinuxThreads version
resides in /lib/i686/libpthread.so.

Under RedHat Linux 9, the version that is linked against depends on
your system's processor:

"On an i686, you get NPTL -- /lib/tls/libpthread.so.0
 On i586, you get LinuxThreads -- /lib/libpthread.so.0" (Bob Holder)

Since I'm getting the NPTL versions and I have a Pentium 4, I presume
that an i686 is a Pentium 4.

The work-around for this is to set the LD_ASSUME_KERNEL environment
variable to the appropriate value (I use 2.4.1):

'"export LD_ASSUME_KERNEL=2.4.1" will "force" LinuxThreads on i686 --
you'll get /lib/i686/libpthread.so.0, and LD_ASSUME_KERNEL=2.2.5 will
force i586 version from /lib/lipthread.so.0'

This information is extracted from the following
comp.programming.threads posting:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&selm=uel0sqyq8.fsfYB8X%40earthlink.net

and is posted here for archival purposes.

Marc A. Criley