Copyright (c) 1998 John D. Polstra
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$FreeBSD: stable/10/lib/libc/gen/dladdr.3 206622 2010-04-14 19:08:06Z uqs $
.Dd February 5, 1998 .Dt DLADDR 3 .Os .Sh NAME .Nm dladdr .Nd find the shared object containing a given address .Sh LIBRARY .Lb libc .Sh SYNOPSIS n dlfcn.h .Ft int .Fn dladdr "const void *addr" "Dl_info *info" .Sh DESCRIPTION The .Fn dladdr function queries the dynamic linker for information about the shared object containing the address .Fa addr . The information is returned in the structure specified by .Fa info . The structure contains at least the following members: l -tag -width "XXXconst char *dli_fname" t Li "const char *dli_fname" The pathname of the shared object containing the address. t Li "void *dli_fbase" The base address at which the shared object is mapped into the address space of the calling process. t Li "const char *dli_sname" The name of the nearest run-time symbol with a value less than or equal to .Fa addr . When possible, the symbol name is returned as it would appear in C source code.
p If no symbol with a suitable value is found, both this field and .Va dli_saddr are set to .Dv NULL . t Li "void *dli_saddr" The value of the symbol returned in .Li dli_sname . .El
p The .Fn dladdr function is available only in dynamically linked programs. .Sh ERRORS If a mapped shared object containing .Fa addr cannot be found, .Fn dladdr returns 0. In that case, a message detailing the failure can be retrieved by calling .Fn dlerror .
p On success, a non-zero value is returned. .Sh SEE ALSO .Xr rtld 1 , .Xr dlopen 3 .Sh HISTORY The .Fn dladdr function first appeared in the Solaris operating system. .Sh BUGS This implementation is bug-compatible with the Solaris implementation. In particular, the following bugs are present: l -bullet t If .Fa addr lies in the main executable rather than in a shared library, the pathname returned in .Va dli_fname may not be correct. The pathname is taken directly from .Va argv[0] of the calling process. When executing a program specified by its full pathname, most shells set .Va argv[0] to the pathname. But this is not required of shells or guaranteed by the operating system. t If .Fa addr is of the form .Va &func , where .Va 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. t Returning 0 as an indication of failure goes against long-standing Unix tradition. .El