sunil wrote:
> Prasently am writing a shared library which is used by one
> application.For that application,am not having the code. I know when
> this library will be called after starting the application(by giving a
> call from the client to that server my .so will be called).

This is typically called a plugin. It would be helpful if you told us which
program you are trying to extend.

> Now sometimes the application crashes after execuion of my shared
> library ( it is printing the last statement of my code before
> returning the value from the function). Am unable to understand why it
> is crashing and how it is crashing. How to identify these kind of
> failures ? Is anybody faced the same scenario, if yes please let me
> know.

There are many insecure things in it that the compiler can't check:
1. Destructors of C++ objects (Note: I'm assuming you are using either C or
C++, it would help if you told us which language!) are run after your last
print statement.
2. Plugin cleanup code. dlclose() invokes a function called _fini() if
present.
3. Interface mismatch. This is the hardest to diagnose, because there is no
runtime checking for it. If for example the program expects a function with
the signature 'int function( float)' and your plugin exports one with the
signature 'float function()', i.e. a different signature, many things can
happen due to the way that C transfers data between functions on the stack.
4. Programming error. Those are simple things like e.g. not passing out
pointers to local memory. Other pitfalls are returning 0 for failure while
it means errorcode E_OK in that context. This list could be endless
though...

Uli

On Nov 13, 9:45 am, Ulrich Eckhardt wrote:
> sunil wrote:
> > Prasently am writing a shared library which is used by one
> > application.For that application,am not having the code. I know when
> > this library will be called after starting the application(by giving a
> > call from the client to that server my .so will be called).
>
> This is typically called a plugin. It would be helpful if you told us which
> program you are trying to extend.
Am customizing the functionality of the product named
webseal(TAM) from IBM

>
> > Now sometimes the application crashes after execuion of my shared
> > library ( it is printing the last statement of my code before
> > returning the value from the function). Am unable to understand why it
> > is crashing and how it is crashing. How to identify these kind of
> > failures ? Is anybody faced the same scenario, if yes please let me
> > know.
>
> There are many insecure things in it that the compiler can't check:
> 1. Destructors of C++ objects (Note: I'm assuming you are using either C or
> C++, it would help if you told us which language!) are run after your last
> print statement.
What you said is correct,am using the C language for my coding.Am
not using C++ thats why there are no issues with the destructors. My
guess it might be related the heap memory issues.
> 2. Plugin cleanup code. dlclose() invokes a function called _fini() if
> present.
I didn't get this dclose function.If possible could u
elaborate on this.

> 3. Interface mismatch. This is the hardest to diagnose, because there is no
> runtime checking for it. If for example the program expects a function with
> the signature 'int function( float)' and your plugin exports one with the
> signature 'float function()', i.e. a different signature, many things can
> happen due to the way that C transfers data between functions on the stack.
> 4. Programming error. Those are simple things like e.g. not passing out
> pointers to local memory. Other pitfalls are returning 0 for failure while
> it means errorcode E_OK in that context. This list could be endless
> though...
>
> Uli

Thanks Uli for u'r kind reply.If u having any ideas on this please let
me know.

Regards
Sunil.

sunil wrote:
> On Nov 13, 9:45 am, Ulrich Eckhardt wrote:
>> 2. Plugin cleanup code. dlclose() invokes a function called _fini() if
>> present.
> I didn't get this dclose function.If possible could u
> elaborate on this.

man dlopen

Uli