rspec/rules/S830/cfamily/rule.adoc

== Why is this an issue?

Having a single declaration of a type, object or function allows the compiler to detect incompatible types for the same entity.


Normally, this will mean declaring an external identifier in a header file that will be included in any file where the identifier is defined or used.


=== Noncompliant code example

[source,cpp]
----
// header.hpp
extern int16_t a;

// file1.cpp
#include "header.hpp"

extern int16_t b;

// file2.cpp
#include "header.hpp"
extern int32_t b; // Noncompliant, compiler may not detect the error
int32_t a; // Compliant, compiler will detect the error
----


=== Compliant solution

[source,cpp]
----
// header.hpp
extern int16_t a; // Compliant, declared once in a header
extern int32_t b; // Compliant, declared once in a header

// file1.cpp
#include "header.hpp"

// file2.cpp
#include "header.hpp"
----


== Resources

* MISRA {cpp}:2008, 3-2-3


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Move the declaration of "xxx" to a header file.


'''
== Comments And Links
(visible only on this page)

=== relates to: S826

=== relates to: S828

=== relates to: S829

=== relates to: S831

endif::env-github,rspecator-view[]