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. 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 structure must be preallocated by the user. The structure members are filled in by dladdr() based on the specified address. The Dl_info structure includes the following members:

const char * dli_fname; void * dli_fbase; const char * dli_sname; void * dli_saddr;

Descriptions of these members appear below.

dli_fname

Contains a pointer to the filename of the containing object.

dli_fbase

Contains the base address of the containing object.

dli_sname

Contains a pointer to the symbol name nearest to the specified address. This symbol either has the same address, or is the nearest symbol with a lower address.

dli_saddr

Contains the actual address of the above symbol.

The dladdr1() function provides for addition information to be returned as specified by the flags argument:

RTLD_DL_SYMENT

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).

RTLD_DL_LINKMAP

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 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 (see Linker and Libraries Guide) and are available to dynamically-linked processes only.

See attributes(5) for descriptions of the following attributes:

ld(1), dlclose(3DL), dldump(3DL), dlerror(3DL), dlopen(3DL), dlsym(3DL), attributes(5)

Linker and Libraries Guide

The Dl_info pointer elements point to addresses within the mapped objects. These may become invalid if objects are removed prior to these elements being used (see dlclose()).

If no symbol is found to describe the specified address, both the dli_sname and dli_saddr members are set to 0.