rspec/rules/S5825/cfamily/rule.adoc

== Why is this an issue?

C provides a way of defining or aliasing a type through ``++typedef++``. On top of it, {cpp} adds ``++using++`` that can do the same and more.


Using a macro to define a type is inferior to the previous ways for two reasons:

* macros cannot be enclosed into scopes. Or at least, doing so is cumbersome and error-prone, as in that case, the macro needs to be defined and undefined manually.
* macros are handled by the preprocessor and are not understood by the compiler. They can easily pollute the code in places where types are not expected. ``++typedef++`` and ``++using++`` are known to the compiler to define types and can be more strictly checked.

As a result, macros should not be used as a replacement for ``++typedef++`` or ``++using++``.


=== Noncompliant code example

[source,cpp]
----
#define UINT unsigned int  // Noncompliant
#define INT int  // Noncompliant
UINT uabs( INT i );
----


=== Compliant solution

[source,cpp]
----
typedef unsigned int UINT;
typedef int INT;
UINT uabs( INT i );
----
or

[source,cpp]
----
using UINT = unsigned int;
using INT = int;
UINT uabs( INT i );
----


== Resources

=== Documentation

* {cpp} reference - https://en.cppreference.com/w/cpp/language/typedef[typedef specifier]
* {cpp} reference - https://en.cppreference.com/w/cpp/language/type_alias[Type alias, alias template]

=== Standards

* CERT - https://wiki.sei.cmu.edu/confluence/display/c/PRE03-C.+Prefer+typedefs+to+defines+for+encoding+non-pointer+types[PRE03-C. Prefer typedefs to defines for encoding non-pointer types]