dlsetlibpath(3C)

NAME

dlsetlibpath() — set the dynamic search path used to locate shared libraries

SYNOPSIS

cc [flag]... file... -ldl [library]...

#include <dlfcn.h>

int dlsetlibpath(const char *libpath, int flags)

Multithread Usage

This routine is thread-safe. Calls to dlsetlibpath() affect all subsequent calls to dlopen(), dlopene(), and dlgetfileinfo(), on any thread.

DESCRIPTION

dlsetlibpath() is one of a family of routines that give the user direct access to the dynamic linking facilities (using the -ldl option on the compiler or ld command line). dlsetlibpath() sets the dynamic search path used by dlopen(), dlopene(), and dlgetfileinfo() to locate shared libraries.

libpath is the dynamic search path. It is a list of one or more path names separated by colons (:).

When searching for a library, the dynamic loader uses search paths in the following default order:

1.: The dynamic search path specified in a call to dlsetlibpath().
2.: The LD_LIBRARY_PATH environment variable.
3.: The SHLIB_PATH environment variable.
4.: The embedded path of the calling module (executable program or shared library) for libraries named in calls to dlopen(), dlopene(), or dlgetfileinfo(). For dependent libraries, the embedded path of the library that named it as a dependent is used.
5.: The standard library path.
6.: The current working directory. (This is only for libraries named in calls to dlopen(), dlopene(), and dlgetfileinfo(), not their dependent libraries.)

(See dld.so(5) for additional information on search paths and options that can change the order described above.)

Any combination of these paths may be disabled by setting flags to one or more of the following flag values OR'ed together. If the following value is set, the dynamic loader does not search the specified location:

RTLD_FLAG_DISABLE_DYNAMIC_PATH: Directories specified in the dynamic search path.
RTLD_FLAG_DISABLE_LD_LIBRARY_PATH: Directories specified in the LD_LIBRARY_PATH environment variable.
RTLD_FLAG_DISABLE_SHLIB_PATH: Directories specified in the SHLIB_PATH environment variable.
RTLD_FLAG_DISABLE_EMBEDDED_PATH: Directories specified in the embedded path.
RTLD_FLAG_DISABLE_STD_PATH: Standard library directory.
RTLD_FLAG_DISABLE_CWD_PATH: Current working directory.

Multiple search paths can be disabled by OR'ing individual flags:

    flags = RTLD_FLAG_DISABLE_STD_PATH | RTLD_FLAG_DISABLE_CWD_PATH

A single search path can be enabled by setting flags to the complement of the flag value that disables that search path:

    flags = ~RTLD_FLAG_DISABLE_DYNAMIC_PATH

EXAMPLES

The following example illustrates the use of dlsetlibpath() to set the dynamic search path and disable other search paths. For simplicity, error checking has been omitted.

          #include <dlfcn.h>

          int main() {
              void *handle;
              int   status;
              int   flags;

              /* Set dynamic search path and disable the embedded
               * path and the standard library directory.
               */
              flags = RTLD_FLAG_DISABLE_EMBEDDED_PATH |
                       RTLD_FLAG_DISABLE_STD_PATH;
              status = dlsetlibpath("/opt/lib:/opt/usr/lib", flags);

              /* Call dlopen to load a library using the dynamic
               * search path.
               */
              handle = dlopen("mylib.so", RTLD_LAZY);

              /* Remove the dynamic search path and reenable all
               * disabled search paths.
               */
              status = dlsetlibpath(NULL, 0);
          }

RETURN VALUE

If successful, dlsetlibpath() returns 0, otherwise a non-0 value is returned. More detailed diagnostic information is available through dlerror() or dlerrno().

ERRORS

If dlsetlibpath() fails, a subsequent call to dlerrno() returns one of the following values:

RTLD_ERR_NO_MEMORY: Cannot allocate dynamic memory.
RTLD_ERR_CANT_APPLY_RELOC: Failed to apply relocation while resolving call to dlsetlibpath().
RTLD_ERR_SIGINHIBIT_FAILED: siginhibit call failed on entry to dlsetlibpath().
RTLD_ERR_SIGENABLE_FAILED: sigenable call failed on exit from dlsetlibpath().
RTLD_ERR_SETCANCELSTATE_FAILED: __thread_setcancelstate failed on entry to or exit from dlsetlibpath().
RTLD_ERR_INV_DLSETLIBPATH_ARGUMENT: Invalid argument in call to dlsetlibpath().

dlsetlibpath(3C)

Technical documentation

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