HP UX Software Transition Kit (STK) Initializer Syntax, Example An Initializer for Each Library

Initializer Syntax

initializer	The name of the initializer as specified with the +I linker option.
handle	The initializer is called with this parameter set to the handle of the shared library for which
	it was invoked.
loading	The initializer is called with this parameter set to 1 (true) when the shared library is loaded
	and 0 (false) when the library is unloaded.

The initializers cannot be defined as local definitions. Initializers cannot be hidden through the use of the -h option when building a shared library. HP recommends that initializers be defined with names which do not cause name collisions with other user-defined names in order to avoid overriding behavior of shared library symbol binding.

Accessing Initializers' Addresses

Prior to the HP-UX 10.0 release, initializer's addresses could be accessed through the initializer field of the shared library descriptor which is returned from a call to shl_get(). To support multiple initializers, the shl_getsymbols() routine is enhanced to support the return of the initializer's address. If only one initializer is specified for a given library, its address is still available through the initializer field of a shared library descriptor. If more than one initializer is specified, the initializer field is set to NO_INITIALIZER. Access to multiple initializers can then be accomplished through the use of shl_getsymbols(). (The shl_getsymbols() routine can also access a single initializer.)

NOTE: The shl_getsymbols() routine may not return the initializer which was invoked for a given library if a more visible initializer symbol is defined after the library being queried has been loaded. This can occur through the use of shl_definesym() and by explicitly loading a more visible symbol using the BIND_FIRST flag upon loading.

To access initializers, use the new flag, INITIALIZERS, in the shl_getsymbols() routine. This flag can be ORed with the NO_VALUES and GLOBAL_VALUES flags. For example,

shl_getsymbols(handle,

TYPE_PROCEDURE,

INITIALIZERS GLOBAL_VALUES, malloc,

&symbol_array);

If the GLOBAL_VALUES modifier is not used and the initializer is defined in another shared library or in the program file, shl_getsymbols() does not find the initializer for the requested library because it is not defined within the library. For more information on the usage of shl_getsymbols(), see The shl_getsymbols Routine.

Example: An Initializer for Each Library

One way to use initializers is to define a unique initializer for each library. For instance, the following example shows the source code for a library named libfoo.so that contains an initializer named init_foo:

C Source for libfoo.c #include <stdio.h> #include <dl.h> /*

*This is the local initializer that is called when the libfoo.so

*is loaded and unloaded:

*/

void init_foo(shl_t hndl, int loading)

{

if (loading) printf("libfoo loaded\n");

else

printf("libfoo unloaded\n");

144 Shared Library Management Routines