[vox-tech] Relocation errors and dynamic symbols

[Peter Jay Salzman]

Hi all,

Continuing from the previous thread on "hello world", we saw an example of a
custom section (.rodata) getting relocated into a canonical section (.text)
in obj or exe files.

But what exactly is a relocation error?  I assume it means there was some
kind of directive to relocate a custom section into canonical section, and if
so, what are the most common causes of such a thing?

Also, looking at the output of nm for an executable:

   080cedf0 T OPdecrement
   080cfd20 T OPdivide
   0821a368 B openbottom
            U opendir@@GLIBC_2.0
            U open@@GLIBC_2.0
   08100820 D OpenGLOptionDef
   08100580 D OpenGLOptionsMenu
   0822ee00 B openings
            U open_music
   0821a36c B openrange
   0821a380 B opentop
   080cef90 T OPequals
   08126d80 D operators
   080cf4c0 T OPgreaterthan

"U" doesn't mean a fatal undefined error; it simply means something that
needs to be linked on the fly by ld.so.  Right?  Is there a way of querying
ld.so about whether it "knows" a particular symbol?

Thanks!
Pete