C++ and "no data fields" when printing objects
Stefano Sabatini
stefano.sabatini-lala@poste.it
Thu Apr 2 13:28:00 GMT 2009
Hi all,
It often occurrs to me to find such situatons when debugging:
(gdb) p ptr
$8 = {
<> = {<No data fields>}, <No data fields>}
and everytime I wonder why the object is not represented meanignfully.
I previously made many researches on the subject, maybe I also already
asked on this list, and came out with the following man of the road
wisdom notions:
1) the problem shows up when you use inlined functions (but the
problem here seems to be related to printing *objects* rather than
step over functions).
2) in order to avoid that you need to use -ggdb -O0
3) it depends on some compiler magic which you really can't
understand
I'm quite sure that even using code compiled with gcc and -ggdb -O0
the abovementioned problem shows anyway.
I'd happily spend months studying the objcode structure and the gdb
internals, but unfortunately I can't, so I'm here to just ask if you
can reply to this questions:
1) which are the conditions under which the abovementioned problem
occurrs (e.g. with shared/static lib, with some arch, only with some
compiler+flags/binary format)?
2) how can I do to be sure not to encounter this problem when
debugging, i.e. which magic do I need to add to the compilation
command, even affecting code size/speed?
Thanks in advance, and thanks for the great tool.
Cheers.
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