On Mar 15, 2008, at 05:59, Derek Ragona wrote:

At 09:49 PM 3/14/2008, Doug Hardie wrote:

On Mar 14, 2008, at 18:31, Derek Ragona wrote:

At 06:56 PM 3/14/2008, Doug Hardie wrote:
There is no code running at that point.  Its just sitting there
waiting for me to enter a gdb command.


On Mar 14, 2008, at 15:16, Derek Ragona wrote:

At 05:10 PM 3/14/2008, Doug Hardie wrote:
I have a program I was testing with gdb.  I was trying to figure
out
why c.rmonths was always zero when it should have been 6. Stepped
through using the gdb n command.  Here is the output:

(gdb)
215                             c.rmonths = (edate - tdate) /
toMONTHS;
(gdb)
223                     c.dial_in = u.dial_in[0];
(gdb)
224                     c.dsl = u.dsl[0];
(gdb) p c.rmonths
$1 = 0
(gdb) p c
$2 = {fa = 0, pwp = 0, disp_email = 0, imonths = 0, rmonths = 6,
  type = 73 'I', cd = 0 '\0', dial_in = 82 'R', dsl = 0 '\0',
  dsl_kit = 0 '\0', ip = 0 '\0', domain = 0 '\0', n_domain = 0
'\0',
  renewal = 89 'Y', program = "I\000\000"}
(gdb) p c->rmonths
$3 = 6
(gdb) p c.rmonths
$4 = 6


Notice, the first time i print it its zero. The second time its 6. What gives here? I have seen this before but couldn't pin it down.
The program is not compiled with any optimization.  It is in a
shared
library though.

It is hard to tell without the code you used.  I would put some
printf's in the code and see what and when that variable gets set to
in actual running code.

        -Derek

I understand it is waiting at a breakpoint in gdb.  What I meant was
put printf's in your code and run the program and look at the
output.  You can use fprintf's to stderr if your prefer and just
look at the stderr output.

It is hard to diagnose what could be a compiler error, or a coding
error.  Remember in C you can do many things you really shouldn't.
It is also advisable to run lint over your source code too.

All that lint shows is it doesn't like comments using // and lots of
errors in /usr/include files.

This sounds more like a c++ program. c++ does a lot of variable initiation in code you usually won't see.

If this is a c++ program, put conditional printf's or cout's in to check the code at actual runtime rather than in the debugger.

You may want to use asserts.

Nope. Very simple c code. I believe as was pointed out earlier that this is a gdb issue. Once gdb found the right value, both it and all the printfs show the correct value. I changed nothing. I am a bit concerned since this is now in a production system that it may eventually start fail again which would have some serious consequences.


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