cpp program

Hello,

are you sure your error appears at run time ?
I think the error you get is at LINK time.
When you create a C / C++ program, you got 2 steps before running you program :

First, the source code is turned into object code so that the cpu can understand it. This is the compilation step.

Then, your program is linked to external libraries or modules. Basically, it's a way to tell to your program where it can find the functions that he calls but that aren't implemented in itself. For example, to use printf() function, your program must be linked to the standard C library.

In your case, the linker tells you that :
 - in the main() function, you called a function named myRecover
 - he knows how to call it (parameters, ...) because you typed the function's prototype at the beginning
 - he don't know in which file he can find the executable where this function is implemented

To make your program work, you must :
 - compile your source file above
 - compile the source file where myRecover is implemented
 - link them together between execution.

The way to specify link options and library is different for every development tool.
Which platform and development tool do you use ?
  MS Visual Studio, Borland, Dev-C++, ... ?
  On Windows, Linux, ... ?

Sorry for double post - browser problem

Not really answering your question but just a little comment on style.

C++ allows you to have a huge number of arguments to a function. However, that doesn't mean it is a good idea to do so. It is easy to get lost in all those 'double' parameters.

A good thing here is to define a class that is used to pass arguments to the function:

instead of
void func(double a, double b, double a2, double b2);


we define first a class to hold the parameters:

class Params {
private:
   double xa, xb, xa2, xb2;

public:
    Params() { /* set default values for each param */ }
    Params & set_a(double x) { xa = x; return *this; }
    Params & set_b(double x) { xb = x; return *this; }
    Params & set_a2(double x) { xa2 = x; return *this; }
    // you get the idea...

    double a() const { return xa; }
    double b() const { return xb; }
    // again you get the idea...
};

void func(const Params & p)
{
   func(p.a(), p.b(), p.a2(), p.b2(), ... );
}

// to call:

void do_something()
{
   func(Params().set_a(4.0).set_b(2.0).set_a2(3.14)...);

   or

   Params p;

   p.set_a(4.0);
   // do some computing...
   p.set_a2(....);
   // now we know what value to set for b...
   p.set_b(....);
   // etc..
   func(p);
}

tend to make the program easier to read AND the caller can set the parameters in the sequence of his or her choice, for example you can set a2 before b etc...

Whenever you have a function with 10 args or more (some would say even 5 or more) you should SERIOUSLY consider this approach.

Alf

ARAVINDBABU,
The Experts cannot help you if you do not respond to questions.  Please don't leave us in suspense!
-- Dan

>> are you sure your error appears at run time ?

Krap, it is possible to get the error at run time. with debugging info(and code) embedded into the program (automatically by the compiler), when an error occurs, the error is captured and displayed just like what aravindbabu says.

one very famous way of doing this is to trap the exceptions and passing it to gdb which with the debug info in the program will tell u wat line contains wat error.

CoolBreeze, do you agree that this error is a LINKER error (ld is a linker !) ?
How can it be possible to have such a link error at run time ? The linkage allways appears before runtime in C/C++, right ?
The only way I know to have runtime linkage is to dynamically load libraries, and I don't remember that this exact error can appear when loading dynamic libraries (and I got so many errors in the past, implementing a plugin system !)
So, it seems to be a linker error, we can see that the program uses multiple source files, and that's why i suspected a build problem...

Let me know if i missed something, or if this exact error can occur at run time (in this case, please tell me how) !

PS : I know what debug info are, and what a debugger can display using them... :-)

hai dan!
    i am sorry .i was sick for four days.that is why i could not respond but today i am back to work i will check out.and thanks for the reply

consider the case of a dynamically linked library. you use an exported function of a dll and compile it into your program. everything works okay. then one day, there comes a new version of the dll, but without the function that you had used. but you did not recompiled your program with the new library. so when you run the program, it causes an error. and with exception handling, the program may be able to output that there is an undefined reference.

the case may be uncommon, but it still exists. and yes i do agree in this case, it is most probably a link problem. juz wanted to point out...

You're right !
I didn't thinked of this case.
Rare, but possible.