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dlinfo (3)

dlinfo (3) ( Solaris man: Библиотечные вызовы )

>> dlinfo (3) ( FreeBSD man: Библиотечные вызовы )

BSD mandoc

NAME

dlinfo

 - information about dynamically loaded object

LIBRARY

Lb libc

SYNOPSIS

#include <link.h>
#include <dlfcn.h>
int dlinfo (void * restrict handle int request void * restrict p);

DESCRIPTION

The dlinfo ();
function provides information about dynamically loaded object. The action taken by dlinfo ();
and exact meaning and type of Fa p argument depend on value of the Fa request argument provided by caller.

The Fa handle argument is either the value returned from the dlopen(3) function call or special handle RTLD_SELF If Fa handle is the value returned from dlopen(3), the information returned by the dlinfo ();
function pertains to the specified object. If handle is the special handle RTLD_SELF the information returned pertains to the caller itself.

Possible values for the Fa request argument are:

RTLD_DI_LINKMAP

Retrieve the Vt Link_map (Vt struct link_map ) structure pointer for the specified Fa handle . On successful return, the Fa p argument is filled with the pointer to the Vt Link_map structure (Fa Link_map **p ) describing a shared object specified by the Fa handle argument. The Vt Link_map structures are maintained as a doubly linked list by ld.so1, in the same order as dlopen(3) and dlclose(3) are called. See Sx EXAMPLES , example 1.

The Vt Link_map structure is defined in #include <link.h>
and has the following members:

caddr_t         l_addr;    /* Base Address of library */
const char      *l_name;   /* Absolute Path to Library */
const void      *l_ld;     /* Pointer to .dynamic in memory */
struct link_map *l_next,   /* linked list of mapped libs */
                *l_prev;

l_addr: The base address of the object loaded into memory.
l_name: The full name of the loaded shared object.
l_ld: The address of the dynamic linking information segment (PT_DYNAMIC ) loaded into memory.
l_next: The next Vt Link_map structure on the link-map list.
l_prev: The previous Vt Link_map structure on the link-map list.

RTLD_DI_SERINFO

Retrieve the library search paths associated with the given Fa handle argument. The Fa p argument should point to Vt Dl_serinfo structure buffer (Fa Dl_serinfo *p ) The Vt Dl_serinfo structure must be initialized first with the RTLD_DI_SERINFOSIZE request.

The returned Vt Dl_serinfo structure contains dls_cnt Vt Dl_serpath entries. Each entry's dlp_name field points to the search path. The corresponding dlp_info field contains one of more flags indicating the origin of the path (see the LA_SER_* flags defined in the #include <link.h>
header file). See Sx EXAMPLES , example 2, for a usage example.

RTLD_DI_SERINFOSIZE

Initialize a Vt Dl_serinfo structure for use in a RTLD_DI_SERINFO request. Both the dls_cnt and dls_size fields are returned to indicate the number of search paths applicable to the handle, and the total size of a Vt Dl_serinfo buffer required to hold dls_cnt Vt Dl_serpath entries and the associated search path strings. See Sx EXAMPLES , example 2, for a usage example.

RTLD_DI_ORIGIN

Retrieve the origin of the dynamic object associated with the handle. On successful return, Fa p argument is filled with the Vt char pointer (Fa char *p )

RETURN VALUES

The dlinfo ();
function returns 0 on success, or -1 if an error occurred. Whenever an error has been detected, a message detailing it can be retrieved via a call to dlerror(3).

EXAMPLES

Example 1: Using dlinfo ();
to retrieve Vt Link_map structure.

The following example shows how dynamic library can detect the list of shared libraries loaded after caller's one. For simplicity, error checking has been omitted.

Link_map *map;

dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map);

while (map != NULL) {
        printf("%p: %s\n", map->l_addr, map->l_name);
        map = map->l_next;
}

Example 2: Using dlinfo ();
to retrieve the library search paths.

The following example shows how a dynamic object can inspect the library search paths that would be used to locate a simple filename with dlopen(3). For simplicity, error checking has been omitted.

Dl_serinfo       _info, *info = &_info;
Dl_serpath      *path;
unsigned int     cnt;

/* determine search path count and required buffer size */
dlinfo(RTLD_SELF, RTLD_DI_SERINFOSIZE, (void *)info);

/* allocate new buffer and initialize */
info = malloc(_info.dls_size);
info->dls_size = _info.dls_size;
info->dls_cnt = _info.dls_cnt;

/* obtain sarch path information */
dlinfo(RTLD_SELF, RTLD_DI_SERINFO, (void *)info);

path = &info->dls_serpath[0];

for (cnt = 1; cnt <= info->dls_cnt; cnt++, path++) {
        (void) printf("%2d: %s\n", cnt, path->dls_name);
}

HISTORY

The dlinfo ();
function first appeared in the Solaris operating system. In Fx , it first appeared in Fx 4.8 .

AUTHORS

An -nosplit The Fx implementation of the dlinfo ();
function was originally written by An Alexey Zelkin Aq phantom@FreeBSD.org and later extended and improved by An Alexander Kabaev Aq kan@FreeBSD.org .

The manual page for this function was written by An Alexey Zelkin Aq phantom@FreeBSD.org .