Linker (ld) takes one or more object files or libraries as input
and combines them to produce a single file.
The dynamic loader (dld) attaches each required library to the process and resolves
all the symbolic references between the program and its libraries.
Is
Summary
of Change |
 |
Both linker and dynamic loader now have support to create
and dynamically load [using dlopen() and shl_load() APIs] shared libraries containing thread local storage
(TLS).
Details
of Change |
|
Two thread local storage models are supported: static and
dynamic, which is controlled by a compiler option +tls=static/dynamic.
The default is +tls=dynamic. Shared libraries
built with the dynamic model can be loaded using dlopen() and shl_load() APIs. An attempt to load a shared library built with
the static model using dlopen() or shl_load() APIs results in the following error:
/usr/lib/hpux[32|64]/dld.so: Can't shl_load() a library containing
Thread Local Storage: /usr/lib/hpux[32|64]/libpthread.so.1
The dynamic loader tallies each shared library's thread local
storage size, as well as, the program's thread local storage size.
When all libraries are loaded, the dynamic loader invokes an initializer
in the system library libc, which does the thread initialization, allocation of
the initial thread, and sets the thread pointer.
Impact |
|
There are no changes to the linker options/usage patterns
with respect to building executables and shared libraries. As long
as +tls=dynamic compiler option is used to create
object files containing TLS, the linker creates load modules with
the dynamic TLS model which in all cases is transparent. There are
no changes to the options provided by the APIs dlopen(), shl_load(), to dld.so flags , and run time options. The dynamic loader operation,
with respect to dynamic TLS support, is transparent.
Compatibility |
|
Applications built on systems prior to HP-UX 11i v1.6 and
moved forward to run on HP-UX 11i v1.6 systems are compatible.
Performance |
|
Due to longer access sequences for TLS variables and more
complex internal data structures, we expect a slight degradation
in performance (within 10%) for applications that heavily use thread
local storage.
Obsolescence |
|
Not applicable.
Documentation |
|
These manpages have been updated accordingly:
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