dladdr, dladdr1 - translate address to symbolic information
int dladdr(void *address, Dl_info_t *dlip);
int dladdr1(void *address, Dl_info_t *dlip, void **info, int flags);
The dladdr() and dladdr1() functions determine if the specified address
is located within one of the mapped objects that make up the current
applications address space. An address is deemed to fall within a
mapped object when it is between the base address, and the _end address
of that object. See NOTES. If a mapped object fits this criteria, the
symbol table made available to the runtime linker is searched to locate
the nearest symbol to the specified address. The nearest symbol is one
that has a value less than or equal to the required address.
The Dl_info_t structure must be preallocated by the user. The structure
members are filled in by dladdr(), based on the specified address. The
Dl_info_t structure includes the following members:
const char *dli_fname;
const char *dli_sname;
The Dl_info_t members provide the following information.
Contains a pointer to the filename of the containing
Contains the base address of the containing object.
Contains a pointer to the symbol name that is nearest to
the specified address. This symbol either represents the
exact address that was specified, or is the nearest symbol
with a lower address.
Contains the actual address of the symbol pointed to by
The dladdr1() function provides for addition information to be returned
as specified by the flags argument:
Obtain the ELF symbol table entry for the matched
symbol. The info argument points to a symbol pointer
as defined in <sys/elf.h> (Elf32_Sym **info or
Elf64_Sym **info). Most of the information found in
an ELF symbol can only be properly interpreted by
the runtime linker. However, there are two fields
that contain information useful to the caller of
dladdr1(): The st_size field contains the size of
the referenced item. The st_info field provides sym‐
bol type and binding attributes. See the Linker and
Libraries Guild for more information.
Obtain the Link_map for the matched file. The info
argument points to a Link_map pointer as defined in
<sys/link.h> (Link_map **info).
If the specified address cannot be matched to a mapped object, a 0 is
returned. Otherwise, a non-zero return is made and the associated
Dl_info_t elements are filled.
The dladdr() and dladdr1() functions are one of a family of functions
that give the user direct access to the dynamic linking facilities.
These facilities are available to dynamically-linked processes only.
See Linker and Libraries Guide.
See attributes(5) for descriptions of the following attributes:
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│MT-Level │ MT-Safe │
SEE ALSOld(1), dlclose(3C), dldump(3C), dlerror(3C), dlopen(3C), dlsym(3C),
Linker and Libraries Guide
The Dl_info_t pointer elements point to addresses within the mapped
objects. These pointers can become invalid if objects are removed prior
to these elements use. See dlclose(3C).
If no symbol is found to describe the specified address, both the
dli_sname and dli_saddr members are set to 0.
If the address specified exists within a mapped object in the range
between the base address and the address of the first global symbol in
the object, the reserved local symbol _START_ is returned. This symbol
acts as a label representing the start of the mapped object. As a
label, this symbol has no size. The dli_saddr member is set to the base
address of the associated object. The dli_sname member is set to the
symbol name _START_. If the flag argument is set to RTLD_DL_SYMENT,
symbol information for _START_ is returned.
If an object is acting as a filter, care should be taken when inter‐
preting the address of any symbol obtained using a handle to this
object. For example, using dlsym(3C) to obtain the symbol _end for this
object, results in returning the address of the symbol _end within the
filtee, not the filter. For more information on filters see the Linker
and Libraries Guide.
Feb 4, 2009 DLADDR(3C)