Relocation Errors

The most common relocation error occurs when a symbol cannot be found. This condition results in an appropriate runtime linker error message and the termination of the application. For example:

$ ldd prog
        libfoo.so.1 =>   ./libfoo.so.1
        libc.so.1 =>     /usr/lib/libc.so.1
        libbar.so.1 =>   ./libbar.so.1
        libdl.so.1 =>    /usr/lib/libdl.so.1
$ prog
ld.so.1: prog: fatal: relocation error: file ./libfoo.so.1: \
symbol bar: referenced symbol not found

The symbol bar, which is referenced in the file libfoo.so.1, cannot be located.

During the link-edit of a dynamic executable, any potential relocation errors of this sort are flagged as fatal undefined symbols. See "Generating an Executable Output File" for examples. This runtime relocation error can occur if the link-edit of main used a different version of the shared object libbar.so.1 that contained a symbol definition for bar, or if the -z nodefs option was used as part of the link-edit.

If a relocation error of this type occurs because a symbol used as an immediate reference cannot be located, the error condition will occur immediately during process initialization. Because of the default mode of lazy binding, if a symbol used as a lazy reference cannot be found, the error condition will occur after the application has gained control. This latter case can take minutes or months, or might never occur, depending on the execution paths exercised throughout the code.

To guard against errors of this kind, the relocation requirements of any dynamic executable or shared object can be validated using ldd(1).

When the -d option is specified with ldd(1), all dependencies will be printed and all immediate reference relocations will be processed. If a reference cannot be resolved, a diagnostic message is produced. From the previous example this option would result in:

$ ldd -d prog
        libfoo.so.1 =>   ./libfoo.so.1
        libc.so.1 =>     /usr/lib/libc.so.1
        libbar.so.1 =>   ./libbar.so.1
        libdl.so.1 =>    /usr/lib/libdl.so.1
        symbol not found: bar           (./libfoo.so.1)

When the -r option is specified with ldd(1), all immediate and lazy reference relocations will be processed. If either type of relocation cannot be resolved, a diagnostic message is produced.