C + + exception handling

A C + + exception handling mechanism

Exception handling Basic idea: the process of executing a function found an exception, can not be processed immediately within the function, but to throw the exception, so that the function of the caller directly or indirectly deal with the problem.

C + + exception handling binary consists of three modules: try, throw, catch

　　Try---Catch basic syntax:

Try     catch (type name [formal parameter name])//{//     catch(type name [formal parameter name])//{  //   catch(..... )//{  

Example:

voidF1 (inti) {    if(i<0)        Throw 1;}voidF2 () {F1 (- $);}voidF3 () {F2 ();}voidF4 () {F3 ();}intMain () {Try{f4 (); }    Catch(inti) {cout<<"Error code:"<< I <<"\ n"<<Endl; } System ("Pause"); return 0;}

Matching rules for two exception captures

What type of exception is thrown inside a try block, and in general, the type must match exactly, but the following three cases can be type-cast:

(1) Run from non-const object to const object conversion, that is, throw a non-const object, catch a const object

(2) running conversions from a derived class type to a base type

(3) Convert an array to a pointer to a group type, and convert the function to a pointer to a function type

voidFuninti) {    if(I <0)        Throw-1;}voidfun2 () {Try{Fun (- at); }    Catch(inti) { switch (i)
{
Case -1;
throw "data out of bounds";  Re-throw
}    }}intMain () { try
{
Fun2 (-34);
}
catch (const char *s)
{
cout << "error code:" << s<<"\ n" << Endl;
}
System ("pause");
return 0;           }

Three exception specification

(1) After the function declaration, list the type of exception that the function might throw, and ensure that the function does not throw other types of exceptions

A. void fun () throw (Toobig,toosmall,divzero); function throws a specified exception

B. void f (); This means that the function throws any kind of exception

C. void f () throw (); This means that the function does not throw an exception

(2) The guarantee does not throw an exception in the constructor, because the function of the constructor is to construct and initialize the object, and once an exception is thrown, it may cause the object to be incomplete or not fully initialized

(3) Guaranteed not to throw an exception in the destructor, because the function of the destructor is to complete the cleanup of resources, once thrown an exception, it is possible to cause memory leaks and so on

C + + exception handling