HP-UX Reference (11i v1 05/09) - 3 Library Functions N-Z (vol 7)

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shl_load(3X) shl_load(3X)

If shl_findsym()

cannot ﬁnd the indicated symbol, errno is set to

0 (zero). On PA-RISC 32-bit sys-

tems only, if

shl_findsym()

ﬁnds the indicated symbol but cannot resolve all the symbols it depends

on,

errno is set to [ENOSYM].

ERRORS

Possible values for

errno include:

[ENOEXEC] The speciﬁed ﬁle is not a shared library, or a format error was detected.

[ENOSYM] Some symbol required by the shared library could not be found.

[EINVAL] The speciﬁed handle or index is not valid or an attempt was made to load a library at

an invalid address.

[ENOMEM] There is insufﬁcient room in the address space to load the library.

[ENOENT] The speciﬁed library does not exist.

[EACCES] Read or execute permission is denied for the speciﬁed library.

WARNINGS

shl_unload() detaches the library from the process and frees the memory allocated for it, but does not

break existing symbolic linkages into the library. In this respect, an unloaded shared library is much like a

block of memory deallocated via free() (see malloc(3C)).

On PA-RISC 32-bit systems, shl_unload() unloads the shared library regardless of whether there are

other references to it. On PA-RISC 64-bit systems, a reference count is kept for each loaded library, and

shl_unload() does not remove the shared library until all references are removed.

Some implementations may not, by default, export all symbols deﬁned by a program (instead exporting only

those symbols that are imported by a shared library seen at link time). Therefore the -E

option to ld(1)

should be used when using these routines if the loaded libraries are to refer to program symbols.

All symbol information returned by

shl_getsymbols()

, including the name ﬁeld, become invalid once

the associated library is unloaded by

shl_unload() . On PA-RISC 64-bit systems, this is also true if a

library is unloaded by a call to dlclose() .

Use caution when building shared libraries with external library dependencies. Any library that contains

Thread Local Storage (TLS) should not be used as a dependency. If a dependent library contains TLS, and

it is not loaded during program startup (that is, not linked against the executable), the dynamic loader fails

to perform the operation.

When a routine or ﬂag is used which may not be supported in the future, the dynamic loader can display a

warning message. See the WARNINGS section in dld.sl(5) for further details.

Future HP-UX 64-bit environments may not support these routines and ﬂags or may only support a subset

of them. Instead, they will use the SVR4 dynamic loading API. Users are encouraged to migrate to the

dl* family of dynamic linking routines. See the dlclose(3C), dlerror(3C), dlget(3C), dlgetname(3C),

dlmodinfo(3C), dlopen(3C), and dlsym(3C) man pages for more information.

AUTHOR

shl_load(3X) and related functions were developed by HP.