GDB Hopelessly broken (CentOS 5.2, debugging Apache QPid)

GDB Hopelessly broken (CentOS 5.2, debugging Apache QPid)

[Joshua Kramer]

Hello Everyone,

I'm having some really bizarre problems debugging Apache Qpid under 
CentOS 5.2, and I'm wondering if anyone can shed some light on this.  
The application is compiled with -ggdb and no optimization (the -O2 
specified in the makefile was removed).

GDB (as supplied by the OS) is exhibiting odd behavior.  First, I keep 
getting the error about the source files being newer than the 
executable, even though:

1. I have manually deleted all object files and executables, then ran 
make, and
2. I verified that the executable is 30 minutes newer than any source file.

Next, it appears that some code does not get compiled.  If I set a 
breakpoint on line 335 of a certain file, it does not stop until line 
339.  Also, some variables do not get declared.  In the code example 
shown below, the seContext variable is never declared - that is, if I 
set the breakpoint on lines directly after I assign something to that 
variable, when gdb stops and I enter the command 'print seContext', gdb 
replies that there is no seContext in this scope.

Are these things a result of unseen compiler optimizations?  Any help is 
greatly appreciated.

Thanks!
-Joshua Kramer

(gdb) list 
/home/josh/dev/qpid/trunk/qpid/cpp/src/qpid/broker/SessionAdapter.cpp:325
320
321     void SessionAdapter::QueueHandlerImpl::declare(const string& 
name, const string& alternateExchange,
322                                                    bool passive, 
bool durable, bool exclusive,
323                                                    bool autoDelete, 
const qpid::framing::FieldTable& arguments)
324     {
325         AclModule* acl = getBroker().getAcl();
326        
327         std::string seContext;
328         //if (arguments.isSet("secontext"))
329         {

(gdb) list 
/home/josh/dev/qpid/trunk/qpid/cpp/src/qpid/broker/SessionAdapter.cpp:343
338             params.insert(make_pair(acl::PROP_EXCLUSIVE, 
std::string(exclusive ? "true" : "false")));
339             params.insert(make_pair(acl::PROP_AUTODELETE, 
std::string(autoDelete ? "true" : "false")));
340            
341             // JPK: Create some parameters from the arguments.
342            
343             //if (arguments.isSet("secontext"))
344                 {
345                     seContext = arguments.getAsString("secontext");
346                     params.insert(make_pair(acl::PROP_SECONTEXT, 
seContext));
347                 }
(gdb)

Re: GDB Hopelessly broken (CentOS 5.2, debugging Apache QPid)

[Paul Pluzhnikov]

On Fri, Apr 17, 2009 at 8:33 PM, Joshua Kramer <josh@globalherald.net> wrote:
> Hello Everyone,
>
> I'm having some really bizarre problems debugging Apache Qpid under CentOS
> 5.2, and I'm wondering if anyone can shed some light on this.  The
> application is compiled with -ggdb and no optimization (the -O2 specified in
> the makefile was removed).
>
> GDB (as supplied by the OS) is exhibiting odd behavior.  First, I keep
> getting the error about the source files being newer than the executable,
> even though:
>
> 1. I have manually deleted all object files and executables, then ran make,
> and
> 2. I verified that the executable is 30 minutes newer than any source file.
>
> Next, it appears that some code does not get compiled.  If I set a
> breakpoint on line 335 of a certain file, it does not stop until line 339.
>  Also, some variables do not get declared.  In the code example shown below,
> the seContext variable is never declared - that is, if I set the breakpoint
> on lines directly after I assign something to that variable, when gdb stops
> and I enter the command 'print seContext', gdb replies that there is no
> seContext in this scope.
>
> Are these things a result of unseen compiler optimizations?  Any help is
> greatly appreciated.

The most likely cause is a "pilot error".

Are you debugging the binary you just rebuilt?
How do you invoke GDB?

All the symptoms you've listed are consistent with you debugging
some *other* optimized binary.


> Thanks!
> -Joshua Kramer
>
> (gdb) list
> /home/josh/dev/qpid/trunk/qpid/cpp/src/qpid/broker/SessionAdapter.cpp:325
> 320
> 321     void SessionAdapter::QueueHandlerImpl::declare(const string& name,
> const string& alternateExchange,
> 322                                                    bool passive, bool
> durable, bool exclusive,
> 323                                                    bool autoDelete,
> const qpid::framing::FieldTable& arguments)
> 324     {
> 325         AclModule* acl = getBroker().getAcl();
> 326        327         std::string seContext;
> 328         //if (arguments.isSet("secontext"))
> 329         {
>
> (gdb) list
> /home/josh/dev/qpid/trunk/qpid/cpp/src/qpid/broker/SessionAdapter.cpp:343
> 338             params.insert(make_pair(acl::PROP_EXCLUSIVE,
> std::string(exclusive ? "true" : "false")));
> 339             params.insert(make_pair(acl::PROP_AUTODELETE,
> std::string(autoDelete ? "true" : "false")));
> 340            341             // JPK: Create some parameters from the
> arguments.
> 342            343             //if (arguments.isSet("secontext"))
> 344                 {
> 345                     seContext = arguments.getAsString("secontext");
> 346                     params.insert(make_pair(acl::PROP_SECONTEXT,
> seContext));
> 347                 }
> (gdb)
>
>



-- 
Paul Pluzhnikov

Re: GDB Hopelessly broken (CentOS 5.2, debugging Apache QPid)

[Jan Kratochvil]

Hi Joshua,

On Sat, 18 Apr 2009 05:33:00 +0200, Joshua Kramer wrote:
> I'm having some really bizarre problems debugging Apache Qpid under  
> CentOS 5.2,

as CentOS-5.3 is available and GDB is rebased from 6.5 to 6.8 (+many other
patches) could you first that one? Building FSF GDB HEAD may also be worth
a try:
http://www.gnu.org/software/gdb/current/
cvs -d :pserver:anoncvs@sourceware.org:/cvs/src co gdb

Still according to your description I would double-check the compilation
command if some -O2 could not crept in.


Regards,
Jan