VHDL1066: Objects of different lengths should not be compared

Summary

Count: 1

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Reliability	Security	Maintainability	Code attribute	Effort to fix	Tags
HIGH	-	-	Intentionality | Logical	30min	synthesis, bug-finder, do254, cnes, cnes-std-06600, do254-cp7, linty-ultra

Description

Noncompliant code example

entity top is
  port (
    A : in std_logic_vector(1 downto 0);
    B : in std_logic_vector(2 downto 0);
    Z : out std_logic
  );
end;

architecture rtl of top is
begin
  process (A, B) is
  begin
    if (A = B) then
      Z <= '1';
    else
      Z <= '0';
    end if;
  end process;
end;

Compliant solution

entity top is
  port (
    A : in std_logic_vector(2 downto 0);
    B : in std_logic_vector(2 downto 0);
    Z : out std_logic
  );
end;

architecture rtl of top is
begin
  process (A, B) is
  begin
    if (A = B) then
      Z <= '1';
    else
      Z <= '0';
    end if;
  end process;
end;

Comparing objects of different lengths always returns false. Thus, such comparisons should be removed.

Parameters

No parameters.