dlerror(3p) [suse man page]

DLERROR(3P)						     POSIX Programmer's Manual						       DLERROR(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       dlerror - get diagnostic information

SYNOPSIS

       #include <dlfcn.h>

       char *dlerror(void);

DESCRIPTION

       The dlerror() function shall return a null-terminated character string (with no trailing <newline>) that  describes  the  last  error  that
       occurred  during  dynamic  linking processing. If no dynamic linking errors have occurred since the last invocation of dlerror(), dlerror()
       shall return NULL.  Thus, invoking dlerror() a second time, immediately following a prior invocation, shall result in NULL being returned.

       The dlerror() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

RETURN VALUE

       If successful, dlerror() shall return a null-terminated character string; otherwise, NULL shall be returned.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       The following example prints out the last dynamic linking error:

	      ...
	      #include <dlfcn.h>

	      char *errstr;

	      errstr = dlerror();
	      if (errstr != NULL)
	      printf ("A dynamic linking error occurred: (%s)
", errstr);
	      ...

APPLICATION USAGE

       The messages returned by dlerror() may reside in a static buffer that is overwritten on each call to dlerror().	 Application  code  should
       not  write  to  this  buffer.  Programs wishing to preserve an error message should make their own copies of that message. Depending on the
       application environment with respect to asynchronous execution events, such as  signals	or  other  asynchronous  computation  sharing  the
       address space, conforming applications should use a critical section to retrieve the error pointer and buffer.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       dlclose(), dlopen(), dlsym(), the Base Definitions volume of IEEE Std 1003.1-2001, <dlfcn.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							       DLERROR(3P)

DLCLOSE(3P)						     POSIX Programmer's Manual						       DLCLOSE(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       dlclose - close a dlopen object

SYNOPSIS

       #include <dlfcn.h>

       int dlclose(void *handle);

DESCRIPTION

       The dlclose() function shall inform the system that the object referenced by a handle returned from a previous dlopen()	invocation  is	no
       longer needed by the application.

       The  use  of  dlclose() reflects a statement of intent on the part of the process, but does not create any requirement upon the implementa-
       tion, such as removal of the code or symbols referenced by handle. Once an object has been closed using	dlclose()  an  application  should
       assume that its symbols are no longer available to dlsym(). All objects loaded automatically as a result of invoking dlopen() on the refer-
       enced object shall also be closed if this is the last reference to it.

       Although a dlclose() operation is not required to remove structures from an address space, neither is  an  implementation  prohibited  from
       doing  so.  The	only  restriction  on  such a removal is that no object shall be removed to which references have been relocated, until or
       unless all such references are removed. For instance, an object that had been loaded with a dlopen() operation specifying  the  RTLD_GLOBAL
       flag  might  provide a target for dynamic relocations performed in the processing of other objects-in such environments, an application may
       assume that no relocation, once made, shall be undone or remade unless the object requiring the relocation has itself been removed.

RETURN VALUE

       If the referenced object was successfully closed, dlclose() shall return 0. If the object could not be closed, or if handle does not  refer
       to an open object, dlclose() shall return a non-zero value. More detailed diagnostic information shall be available through dlerror().

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       The following example illustrates use of dlopen() and dlclose():

	      ...
	      /* Open a dynamic library and then close it ... */

	      #include <dlfcn.h>
	      void *mylib;
	      int eret;

	      mylib = dlopen("mylib.so", RTLD_LOCAL | RTLD_LAZY);
	      ...
	      eret = dlclose(mylib);
	      ...

APPLICATION USAGE

       A conforming application should employ a handle returned from a dlopen() invocation only within a given scope bracketed by the dlopen() and
       dlclose() operations. Implementations are free to use reference counting or other techniques such that multiple calls to dlopen() referenc-
       ing  the  same object may return the same object for handle.  Implementations are also free to reuse a handle. For these reasons, the value
       of a handle must be treated as an opaque object by the application, used only in calls to dlsym() and dlclose().

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       dlerror(), dlopen(), dlsym(), the Base Definitions volume of IEEE Std 1003.1-2001, <dlfcn.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							       DLCLOSE(3P)