rspec/rules/S5658/cfamily/rule.adoc

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

----
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

----
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
  {
  }
}
----

== See

* 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.
* https://github.com/isocpp/CppCoreGuidelines/blob/036324/CppCoreGuidelines.md#es62-dont-compare-pointers-into-different-arrays[{cpp} Core Guidelines ES.62] - Don't compare pointers into different arrays