va_start
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <cstdarg> | ||
| void va_start( va_list ap, parm_n ); | ||
The va_start macro enables access to the variable arguments following the named argument parm_n.  
va_start should be invoked with an instance to a valid va_list object ap before any calls to va_arg.
If parm_n is declared with reference type or with a type not compatible with the type that results from default argument promotions, the behavior is undefined.
| Contents | 
[edit] Parameters
| ap | - | an instance of the va_list type | 
| parm_n | - | the named parameter preceding the first variable parameter | 
[edit] Expanded value
(none)
[edit] Notes
va_start is required to support parm_n with overloaded operator&.
[edit] Example
Run this code
Output:
150
[edit] See also
| accesses the next variadic function argument (function macro) | |
| ends traversal of the variadic function arguments (function macro) | |
| C documentation for va_start | |


