DLADDR(3)              FreeBSD Library Functions Manual              DLADDR(3)

NAME
     dladdr - find the shared object containing a given address

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <dlfcn.h>

     int
     dladdr(const void *addr, Dl_info *info);

DESCRIPTION
     The dladdr() function queries the dynamic linker for information about
     the shared object containing the address addr.  The information is
     returned in the structure specified by info.  The structure contains at
     least the following members:

     const char *dli_fname     The pathname of the shared object containing
                               the address.

     void *dli_fbase           The base address at which the shared object is
                               mapped into the address space of the calling
                               process.

     const char *dli_sname     The name of the nearest run-time symbol with a
                               value less than or equal to addr.  When
                               possible, the symbol name is returned as it
                               would appear in C source code.

                               If no symbol with a suitable value is found,
                               both this field and dli_saddr are set to NULL.

     void *dli_saddr           The value of the symbol returned in dli_sname.

     The dladdr() function is available only in dynamically linked programs.

ERRORS
     If a mapped shared object containing addr cannot be found, dladdr()
     returns 0.  In that case, a message detailing the failure can be
     retrieved by calling dlerror().

     On success, a non-zero value is returned.

SEE ALSO
     rtld(1), dlopen(3)

HISTORY
     The dladdr() function first appeared in the Solaris operating system.

BUGS
     This implementation is bug-compatible with the Solaris implementation.
     In particular, the following bugs are present:

     •   If addr lies in the main executable rather than in a shared library,
         the pathname returned in dli_fname may not be correct.  The pathname
         is taken directly from argv[0] of the calling process.  When
         executing a program specified by its full pathname, most shells set
         argv[0] to the pathname.  But this is not required of shells or
         guaranteed by the operating system.

     •   If addr is of the form &func, where func is a global function, its
         value may be an unpleasant surprise.  In dynamically linked programs,
         the address of a global function is considered to point to its
         program linkage table entry, rather than to the entry point of the
         function itself.  This causes most global functions to appear to be
         defined within the main executable, rather than in the shared
         libraries where the actual code resides.

     •   Returning 0 as an indication of failure goes against long-standing
         Unix tradition.

FreeBSD 13.1-RELEASE-p6        February 5, 1998        FreeBSD 13.1-RELEASE-p6