HP-UX Linker and Libraries User's Guide

Dynamic Path Searching for Shared Libraries
Any library whose name has no "/" character in it becomes a candidate for dynamic path
searching. Also, the linker always uses the LD_LIBRARY_PATH and the SHLIB_PATH environment
variable to add directories to the run time search path for shared libraries, unless the ld
+noenvvar option is set.
In PA-32 compatibility mode of the linker toolset (selected by the +compat option), the linker
enables run-time dynamic path searching when you link a program with the -llibrary and +b
path_name options. Or, you can use the -llibrary option with the +s path_name option. When
programs are linked with +s, the dynamic loader searches directories specified by the SHLIB_PATH
environment variable to find shared libraries.
The following example shows dynamic path searching changes for default mode.
$ ld main.o \ Subject to
-lfoo -o main dynamic path searching.
The dynamic loader searches for libfoo.so in the directories specified by the LD_LIBRARY_PATH
and SHLIB_PATH environment variables.
Shared Library Symbol Binding Semantics
Symbol binding resolution, both at link time and run time, changes slightly in the IPF and PA-64
HP-UX linker toolset. The symbol binding policy is more compatible with other open systems.
This section covers the following topics:
• Link-time symbol resolution in shared libraries
• Resolution of unsatisfied shared library references
• Promotion of uninitialized global variables
• Symbol searching in dependent libraries
Link-Time Symbol Resolution in Shared Libraries
In the IPF and PA-64 linker toolset, the linker remembers all symbols in a shared library for the
duration of the link. Global definitions satisfy trailing references, and unsatisfied symbols remaining
in shared libraries are reported.
The PA-32 linker does not remember the definition of a procedure in a shared library unless it was
referenced in previously scanned object files.
If you have function names that are duplicated in a shared and archive library, the IPF and PA-64
linker may reference a different version of a procedure than is referenced by the PA-32 mode
linker. This change can lead to unexpected results.
For example, given these source files:
sharedlib.c
void afunc()
{
printf("\tin SHARED library procedure 'afunc'\n");
}
unsat.c
void bfunc()
{
afunc();
}
archive.c
126 Creating and Using Libraries