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Non-initialized variable

Variable not initialized before use

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Description

This defect occurs when a variable is not initialized before its value is read.

Risk

Unless a variable is explicitly initialized, the variable value is unpredictable. You cannot rely on the variable having a specific value.

Fix

The fix depends on the root cause of the defect. For instance, you assigned a value to the variable but the assignment is unreachable or you assigned a value to the variable in one of two branches of a conditional statement. Fix the unreachable code or missing assignment.

Often the result details (or source code tooltips in Polyspace as You Code) show a sequence of events that led to the defect. You can implement the fix on any event in the sequence. If the result details do not show this event history, you can search for previous references of variables relevant to the defect using right-click options in the source code and find related events. See also Interpret Bug Finder Results in Polyspace Desktop User Interface or Interpret Bug Finder Results in Polyspace Access Web Interface (Polyspace Access).

See examples of fixes below. It is a good practice to initialize a variable at declaration.

If you do not want to fix the issue, add comments to your result or code to avoid another review. See:

Extend Checker

You can extend the checker in the following ways:

Examples

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int get_sensor_value(void)
{
    extern int getsensor(void);
    int command;
    int val;

    command = getsensor();
    if (command == 2) 
      {
        val = getsensor();
      }

    return val;              
    /* Defect: val does not have a value if command is not 2 */
}

If command is not 2, the variable val is unassigned. In this case, the return value of function get_sensor_value is undetermined.

Correction — Initialize During Declaration

One possible correction is to initialize val during declaration so that the initialization is not bypassed on some execution paths.

int get_sensor_value(void)
{
    extern int getsensor(void);
    int command;
    /* Fix: Initialize val */
    int val=0;

    command = getsensor();
    if (command == 2) 
      {
        val = getsensor();
      }

    return val;              
 }

val is assigned an initial value of 0. When command is not equal to 2, the function get_sensor_value returns this value.

Result Information

Group: Data flow
Language: C | C++
Default: On
Command-Line Syntax: NON_INIT_VAR
Impact: High

Version History

Introduced in R2013b

See Also

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