RE: [PATCH v4] gdb, gdbserver: support dlmopen()

["Metzger, Markus T" <markus.t.metzger@intel.com>]

Hello Tom,

>Markus> +  /* There may be different instances of the same library, in different
>Markus> +     namespaces.  Each instance, however, must have been loaded at a
>Markus> +     different address so its relocation offset would be different.  */
>Markus> +  const lm_info_svr4 *lmg = (const lm_info_svr4 *) gdb->lm_info;
>Markus> +  const lm_info_svr4 *lmi = (const lm_info_svr4 *) inferior->lm_info;
>Markus> +
>Markus> +  return (lmg->l_addr_inferior == lmi->l_addr_inferior);
>
>Can you explain how objfile handling works?
>
>I'd suspect that just a single objfile will be made for a given .so.
>But, if that comment is correct (I think it is) then that would be
>wrong, because an objfile has to know the correct runtime offset.

GDB creates separate objfile objects per instance.  I placed a breakpoint at
symbol_file_add_with_addrs and compared the objfile * returned from
objfile::make().

See also the output of 'maint print objfiles':
[...]
Object file /users/mmetzger/gdb/build/dlmopen-fc35/gdb/testsuite/outputs/gdb.base/dlmopen/dlmopen-lib.1.so:  Objfile at 0x4bec900, bfd at 0x4ee7f60, 19 minsyms

Psymtabs:
/users/mmetzger/gdb/git/gdb/testsuite/gdb.base/dlmopen-lib.c at 0x4d05200

Object file /users/mmetzger/gdb/build/dlmopen-fc35/gdb/testsuite/outputs/gdb.base/dlmopen/dlmopen-lib.1.so:  Objfile at 0x4beee90, bfd at 0x4ee7f60, 19 minsyms

Psymtabs:
/users/mmetzger/gdb/git/gdb/testsuite/gdb.base/dlmopen-lib.c at 0x4d05200
[...]

Regards,
Markus.
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