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enumssystem-verilog
Victor L
Victor L

Reputation: 10220

Can SystemVerilog enums be null?

I'm using enum method name() to print the string value of an enum variable.

Should I do a null check first?

Upvotes: 2

Views: 1808

Answers (2)

Greg
Greg

Reputation: 19094

The name() method cannot return null. It will return an empty string if the value does not correspond to an enumerated value. It may be advisable to do an empty string check.

Quoting from IEEE std 1800-2012 § 6.19.5.6 Name()

The name() method returns the string representation of the given enumeration value. If the given value is not a member of the enumeration, the name() method returns the empty string.

Upvotes: 3

Victor L
Victor L

Reputation: 10220

No, you don't need to worry about a null enum. However, an enum could be un-initialized if it does not have a state corresponding to 0

For example:

typedef enum {STATE0, STATE1} plain_enum;
typedef enum {VAL0=1, VAL1} special_enum;

module test;

  initial begin
    plain_enum plain;
    special_enum special;
    $display("plain: %s", plain.name());
    $display("special: %s", special.name());
  end

endmodule

Returns:

# plain: STATE0
# special:

Because special_enum does not have a state corresponding to 0

Edit/re-run the code here: http://www.edaplayground.com/s/4/647

Upvotes: 1

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