Login | Register   
RSS Feed
Download our iPhone app
Browse DevX
Sign up for e-mail newsletters from DevX

By submitting your information, you agree that devx.com may send you DevX offers via email, phone and text message, as well as email offers about other products and services that DevX believes may be of interest to you. DevX will process your information in accordance with the Quinstreet Privacy Policy.


There's More to Typecasting than C++ Cast Operators : Page 2

Knowing exactly which typecasting operation is required for a given task and familiarity with the little known techniques that automate type conversions is essential--even in state-of-the-art C++ projects.




Building the Right Environment to Support AI, Machine Learning and Deep Learning

Presenting the Problem
When I introduced C++ cast operators more than six years ago, I truly wanted to believe that they were the right thing to use in through and through C++ programs. And yet, numerous questions from readers and my own experience have made me question C++ cast operators. This doesn't mean that you should throw C++ cast operators out of the window. However, you should familiarize yourself with alternative cast techniques to produce better code.

Cast Away
In spite of the frowns with which C-style cast is often greeted, it's a powerful and smart tool. The syntax is simple: enclose the target type in a pair of parentheses and place the argument after the parentheses. The following example casts a function pointerto long using C-style cast:

void myfunc(bool) 
void (*pf) (bool) = myfunc;
long long val= (long long) myfunc;

Replacing C-style with C++ cast operators will put you in a dilemma—should you use static_cast or reinterpret_cast? The "recommended" solution is to start with static_castand see if it works:

long long val= static_cast<long long> (myfunc);

Notice how verbose and ugly this statement is compared to the elegance and compactness of C-style cast. But it get worse—this code doesn't even compile. You need to use reinterpret_cast here, not static_cast:

long long val= 
 reinterpret_cast<long long> (myfunc); //ugly but works

No wonder why many C++ programmers give up static_cast entirely and stick to reinterpret_casteven when it's wrong.

Unlike C++ cast operators, a single C-style cast expression can perform two different conversions at once as shown in the following example:

void func(unsigned char * data);//doesn't modify data
const char txt[]="ABC";
func ((unsigned char*) txt);//remove const, add unsigned

C++ pundits didn't like this because the code is purportedly not explicit enough. However, using C++ cast notation makes the code extremely obfuscated, which doesn't exactly make your code clearer or safer:

func (reinterpret_cast<unsigned char *>
(const_cast<char *>(txt)));//remove const, add unsigned

Comment and Contribute






(Maximum characters: 1200). You have 1200 characters left.



Thanks for your registration, follow us on our social networks to keep up-to-date