C compiler issue perhaps?

[Doug Hardie]

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.