Our website uses cookies to enhance your browsing experience.
Accept
to the top
close form

Fill out the form in 2 simple steps below:

Your contact information:

Step 1
Congratulations! This is your promo code!

Desired license type:

Step 2
Team license
Enterprise license
** By clicking this button you agree to our Privacy Policy statement
close form
Request our prices
New License
License Renewal
--Select currency--
USD
EUR
* By clicking this button you agree to our Privacy Policy statement

close form
Free PVS‑Studio license for Microsoft MVP specialists
* By clicking this button you agree to our Privacy Policy statement

close form
To get the licence for your open-source project, please fill out this form
* By clicking this button you agree to our Privacy Policy statement

close form
I am interested to try it on the platforms:
* By clicking this button you agree to our Privacy Policy statement

close form
check circle
Message submitted.

Your message has been sent. We will email you at


If you haven't received our response, please do the following:
check your Spam/Junk folder and click the "Not Spam" button for our message.
This way, you won't miss messages from our team in the future.

>
>
>
V721. The VARIANT_BOOL type is used inc…
menu mobile close menu
Analyzer diagnostics
General Analysis (C++)
General Analysis (C#)
General Analysis (Java)
Micro-Optimizations (C++)
Diagnosis of 64-bit errors (Viva64, C++)
Customer specific requests (C++)
MISRA errors
AUTOSAR errors
OWASP errors (C#)
Problems related to code analyzer
Additional information
toggle menu Contents

V721. The VARIANT_BOOL type is used incorrectly. The true value (VARIANT_TRUE) is defined as -1.

Mar 31 2015

The analyzer has detected an incorrect use of the VARIANT_BOOL type. The reason is that the value true (VARIANT_TRUE) is designated as -1. Many programmers are unaware of this detail and tend to use this type incorrectly.

This is how the VARIANT_TRUE type and constants denoting "true" and "false" are declared:

typedef short VARIANT_BOOL;
#define VARIANT_TRUE ((VARIANT_BOOL)-1)
#define VARIANT_FALSE ((VARIANT_BOOL)0)

Let's take a look at a few examples when the VARIANT_TRUE type is used incorrectly. In all the cases, the programmer expects the condition to be true, while it is actually always false.

Example 1.

VARIANT_BOOL variantBoolTrue = VARIANT_TRUE;
if (variantBoolTrue == true) //false

If we substitute the value into the expression, we'll get ((short)(-1) == true). When this expression is evaluated, 'true' will turn into '1'. The condition (-1 == 1) is false.

The correct code:

if (variantBoolTrue == VARIANT_TRUE)

Example 2.

VARIANT_BOOL variantBoolTrue = TRUE;
if (variantBoolTrue == VARIANT_TRUE) //false

The programmer made a mistake here and used TRUE instead of VARIANT_TRUE. It will result in the variantBoolTrue variable being assigned the value 1. This value is illegal for variables of the VARIANT_BOOL type.

If we substitute the value into the expression, we will get (1 == (short)(-1)).

The correct code:

VARIANT_BOOL variantBoolTrue = VARIANT_TRUE;

Example 3.

bool bTrue = true;
if (bTrue == VARIANT_TRUE) //false

Let's expand the expression: (true == (short)(-1)). When it is evaluated, 'true' will turn into '1'. The condition (1 == -1) is false.

It's not easy to suggest a correct version of this code as it is just fundamentally incorrect. One can't mix variables of the 'bool' type and values of the 'VARIANT_TRUE' type.

There are numbers of other examples like these to be found in code. For instance, when a function's formal argument is of the VARIANT_BOOL type but it is the 'true' value that will be passed as the actual one. Another example is when a function returns an incorrect value. And so on and so forth.

The most important thing you should keep in mind is that you can't mix the VARIANT_BOOL type with the types BOOL, bool, and BOOLEAN.

References:

This diagnostic is classified as:

You can look at examples of errors detected by the V721 diagnostic.