_ Declspec (noreturn) Usage

_ Declspec (noreturn) Usage

Floating white clouds 2008.11.26 first look at the annotation of noreturn in msdn:

A function is _ Declspec (noreturn)As agreed, it means to tell the compiler that this function will not be returned, and the result is to let the compiler know that the call convention is _ Declspec (noreturn)The code after the function is not reachable.
If the compiler finds that a function has a code branch with no return value, the compiler reports a c4715 warning or c2202 error message. If this code branch cannot be reached because the function does not return, you can use the Convention. _ Declspec (noreturn)To avoid the above warnings or errors.

Note:
Convention on a function to be returned_ Declspec (noreturn)Will lead to undefined behavior.

Example:

In the following example, the main function is notElseBranch return, so the agreed FunctionFatalIs_ Declspec (noreturn)To avoid compilation or warning.

// noreturn2.cpp__declspec(noreturn) extern void fatal () {}int main() { if(1) return 1; else if(0) return 0; else fatal();}

----------------------------------------------------------- Another purpose is to use _ Declspec (noreturn)To define the throw function. Therefore, when an exception is thrown, the subsequent statement is not executed. Example:

1. // Exception
2. Class exception {
3. Public:
4. Virtual ~ Exception ()
5. {
6. }
7. };
8. // Exception
10. // Logicalerror
11. Class logicalerror:
12. Public exception {
13. Cstringw m_message;
14. Public:
15. Logicalerror (lpcwstr MSG ):
16. M_message (MSG)
17. {
18. }
20. Virtual ~ Logicalerror ()
21. {
22. }
24. Lpcwstr getmessage () const
25. {
26. Return m_message;
27. }
29. Static void decl_noreturn throw (lpcwstr MSG)
30. {
31. Throw logicalerror (MSG );
32. }
33. };

In use, the code will not be executed after the throw statement is called.

For example: lpcwstr getstring (File * FP) {If (FP = NULL) {logicalerror: Throw (L "getstring (File * FP): file handle FP is null! ");}......}