rspec/rules/S5658/cfamily/rule.adoc

== Why is this an issue?

Attempting to make a comparison between pointers using >, >=, < or +<=+ will produce undefined behavior if the two pointers point to different arrays.

Additionally, directly comparing two arrays for equality or inequality has been deprecated in {cpp}. 

However, equality or inequality between an array and a pointer is still valid


=== Noncompliant code example

[source,cpp]
----
void f1 ( )
{
  int a1[ 10 ];
  int a2[ 10 ];
  int * p1 = a1;
  if ( p1 < a2 ) // Non-compliant, p1 and a2 point to different arrays.
  {
  }
  if ( p1 - a2 > 0 ) // Non-compliant, p1 and a2 point to different arrays.
  {
  }
  if ( a1 == a2) // Non-compliant (in C++). Comparing different array for equality is deprecated
  {
  }
}
----


=== Compliant solution

[source,cpp]
----
void f1 ( )
{
  int a1[ 10 ];
  int * p1 = a1;
  if ( p1 < a1 ) // Compliant, p1 and a1 point to the same array.
  {
  }
  if ( p1 - a1 > 0 )  // Compliant, p1 and a1 point to the same array.
  {
  }
  if ( p1 == a2 ) // Compliant, comparing a pointer and an array for equality is valid
  {
  }
}
----


== Resources

* MISRA C:2004, 17.3 - >, >=, <, +<=+ shall not be applied to pointer types except where they point to the same array.
* MISRA {cpp}:2008, 5-0-18 - >, >=, <, +<=+ shall not be applied to objects of pointer type, except where they point to the same array.
* {cpp} Core Guidelines - https://github.com/isocpp/CppCoreGuidelines/blob/e49158a/CppCoreGuidelines.md#es62-dont-compare-pointers-into-different-arrays[ES.62: Don't compare pointers into different arrays]


ifdef::env-github,rspecator-view[]
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== Comments And Links
(visible only on this page)

=== is related to: S939

=== is related to: S940

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