# V3079. The 'ThreadStatic' attribute is applied to a non-static 'A' field and will be ignored.

The analyzer detected a suspicious declaration of a non-static field, to which the 'ThreadStatic' attribute is applied.

Using this attribute with a static field allows one to set an individual value for this field for each thread. Besides, it prohibits simultaneous access to this field by different threads, thus eliminating the possibility of mutual exclusion when addressing the field. However, this attribute is ignored when used with a non-static field.

Consider the following example:

    [ThreadStatic]
    bool m_knownThread;

This field looks like a flag that must have individual values for each thread. But since the field is not static, applying the 'ThreadStatic' attribute to it does not make sense. If the program's logic does imply that the field must have a unique value for each thread (as suggested by its name and the presence of the 'ThreadStatic' attribute), there is probably an error in this code.

To fix the error, we need to add the 'static' modifier to the field declaration:

    [ThreadStatic]
    static bool m_knownThread;

References:

- ThreadStaticAttribute Class.

This diagnostic is classified as:

CWE-821

You can look at examples of errors detected by the V3079 diagnostic.