Proper way to define type (typedef vs #define)
Which of these methods is more secure for defining variable types? I know that we all frown when we see #defines, but it seems to work just as well as typedef here:
Is there an advantage one way or the other, and if so what might it be?
Method One:
#include <iostream>
#define byte unsigned char
int main() {
byte testByte = 'A';
std::cout << testByte << std::endl;
return 0;
}
Method Two:
#include <iostream>
int main() {
typedef unsigned char byte;
byte testByte = 'A';
std::cout << testByte << std::endl;
return 0;
}
You should always use the 2nd one (ie typedef or using).
Try to not use macros in c++ as far as possible, and most cases could be avoided. They're just text replacement before compiling, and more "dangerous". eg
#define byte_pointer unsigned char*
byte_pointer p, q; // only p is a pointer
Only one of your examples actually is a way to define a type, so there's no contest between them.
#define byte unsigned char
This just makes all utterances of byte in your code get replaced with unsigned char before compilation begins. It does not define a type.
The declaration int byte; will become int unsigned char; , which is nonsense.
typedef unsigned char byte;
This defines a type. The type will be subject to syntax rules, scoping rules and all of that lovely stuff.
The declaration int byte; will still be the declaration int byte; , because byte here is found in the space for a variable name.
using byte = unsigned char;
This is the "modern" way to define a type alias, which has much clearer syntax than a typedef statement (especially for more complex types).
It was introduced because otherwise the new syntax for template type aliases would have been next to impossible to make sane.
Using #define is not safe (see other answer) Using typedef is the usual way to define types aliases.
There's also the new "using" syntax
using MyByte = unsigned char;
see this answer to a related question (typedef vs. using) https://stackoverflow.com/a/10748056/446303
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